Chantier Infrastructures et Ouvrages d’art Mission technique sur les ponts en aluminium
Endroit : Tampa Bay, Floride
Date : 28 et 29 octobre 2015
Préparé par : Denis Beaulieu et Jacques Internoscia
1- BUT DE LA MISSION
Une première rencontre a eu lieu à Tampa Bay, Floride, le 26 février 2015 entre le groupe de Greg Osberg d’AlumaBridge et une délégation du Québec, composée de Jacques Internoscia, Martin Hartlieb et Denis Beaulieu. Cette rencontre avait pour but de préparer le terrain pour une rencontre plus formelle entre le groupe de développement de platelages et de tabliers de ponts en aluminium des États-Unis et une délégation de représentants de divers organismes québécois et ontariens ayant un intérêt dans le développement et l’utilisation d’un tel produit au Canada.
La deuxième rencontre qui s’est déroulée du 28 au 29 octobre 2015 à Tampa Bay, à nouveau, a permis à la délégation d’industriels, d’universitaires et de représentants d’organismes publics du Québec et de l’Ontario de prendre connaissance, en détail, des plus récents développements réalisés aux États-Unis pour le remplacement des platelages en grillage métallique des ponts mobiles de l’État de la Floride par des platelages d’aluminium. Sept délégués du Québec étaient présents sur place pour rencontrer six représentants américains de l’équipe de Greg Osberg. Lors de la principale rencontre du 29 novembre, en avant-midi, 16 autres personnes, qui n’ont pas pu effectuer le déplacement en Floride, se sont joints à la discussion par conférence téléphonique de type Go-To-Meeting.
2- PARTICIPANTS À LA RENCONTRE
Les hôtes américains : - Greg Osberg, President & CEO, AlumaBridge, [email protected] - George Patton, Hardesty & Hanover, Movable Bridge Design Lead,
[email protected] - Don Foster, Manor Associates, [email protected] - Mike Riley, L.B. Foster, Marketing Manager, Bridge group, [email protected] - Randy Kissel, TGB Partneurship, (AAA representative), [email protected] - Richard Molloy, AlumaBridge Administrator, [email protected] - R. Randy Johnson, Seacoast Inc., Vice President (visité le 29 PM), [email protected]
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La délégation québécoise:
- Jacques Internoscia, Coprésident Chantier Infrastructure et Ouvrage d’Art, AAC, [email protected]
- Denis Beaulieu, Consultant, [email protected] - Daniel Néron, Canmec, Directeur développement corporatif, [email protected] - Éric Lévesque, Canam Ponts, Directeur du Développement Commercial,
[email protected] - Sofiene Amira, CMQ, CEGEP de Trois-Rivières, [email protected] - Charles-Darwin Hannan, REGAL, Département de Génie Civil, Université Laval,
[email protected] - Alexandre de la Chevrotière, MAADI Group, Président, [email protected]
Les participants de l’extérieur (Go-To-Meeting):
- Martin Hartlieb, AluQuébec, [email protected] - Tom Waits, FDOT Structures Design Office, Project Manager, [email protected] - Tony Merlo, MTO, Manager, Bridge Office, [email protected] - David Lai, MTO, Bridge Rehabilitation, [email protected] - Ranko Mihaljevic, MTO, Head, Bridge Standards, [email protected] - Kris Mermigas, MTO, Head, Bridge Management, [email protected] - Walter Kenedi, MTO, Head, Bridge Design, [email protected] - Magdy Meleka, MTO, Lead, Bridge Engineer, [email protected] - Jim Au, MTO, Lead, Bridge Engineer, [email protected] - Jim Connell, MTO, Lead, Bridge Engineer, [email protected] - Gérard Desgagné, MTQ, Chef du Service de la Conception des Structures,
[email protected] - Marcel Vallières, MTQ, Direction des Structures, [email protected] - Dominic Fortin, MTQ, Direction des Structures, [email protected] - Andrew Werblinski, Parks Canada, Senior Structural Engineer,
[email protected] - Scott Walbridge, University of Waterloo, [email protected] - Dominic Vachon, Ville de Montréal, Chef de groupe - conception et normalisation,
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CONTENU
1- But de la mission .................................................................................................................................. 1
2- Participants à la rencontre .................................................................................................................... 1
3- Déroulement de la rencontre de deux jours .......................................................................................... 4
4- Les travaux d’AlumaBridge et de son équipe ....................................................................................... 5
5- L’étude comparative du FDOT .............................................................................................................. 8
6- Programmes de développement, d’analyse et de recherche ............................................................. 11
7- Le Pont de St-Ambroise ...................................................................................................................... 18
Conclusion .............................................................................................................................................. 23
Annexes
Aluminum Bridge Decking
5-inch Aluminum Orthotropic Deck Research and Development
Bascule bridge lightweight solid deck; Retrofit research project
Lightweight prefabricated bridge deck – Scope of services
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3- DÉROULEMENT DE LA RENCONTRE DE DEUX JOURS
Journée du 28 octobre
Une rencontre informelle a été tenue en après-midi avec Greg Osberg afin de faire le point sur le projet du Pont de St-Ambroise avant d’aborder la question dans sa présentation plus officielle du lendemain.
Journée du 29 octobre, en avant-midi
La participation en personne et au téléphone à l’importante rencontre de l’avant-midi a été très bonne.
La matinée a débuté par une présentation technique de l’évolution des solutions techniques développées par AlumaBridge. Greg Osberg a présenté en détail et de façon factuelle des cas concrets, dont le projet de Saint-Ambroise. Voir à cet effet la présentation Adobe Acrobat Reader intitulée AlumaBridge Presentation, 10-29-15 disponible sur le site web d’AluQuébec.
Cette présentation a été suivie de l’intervention de Tom Waits du FDOT qui a présenté le projet de réhabilitation des ponts mobiles de Floride, dont le pilote de Fort Pierce, et l’étude comparative qui avait été effectuée pour la sélection des matériaux. Voir à cet effet le document Adobe Acrobat Reader intitulé Lightweight Solid Deck Alternatives Evaluation FINAL (05-14-13) disponible sur le site web d’AluQuébec. Le titre du rapport est Bascule bridge lightweight solid deck retrofit research project – Deck alternative screening report – Final, FDOT, prepared by URS, May 14, 2012.
George Patton, le concepteur du platelage d’AlumaBridge, a ensuite complété les aspects techniques de la présentation de Greg Osberg et a décrit plus en détail de projet de Fort Pierce. Voir à cet effet la présentation Adobe Acrobat Reader intitulée Aluminum Deck Meeting (10-29-2015) disponible sur le site web d’AluQuébec. Il a mentionné que près de 1200 ponts mobiles devront être réhabilités aux États-Unis, dont un bon nombre en Floride, et que la technologie d’AlumaBridge s’applique aussi bien aux ponts fixes que mobiles.
Beaucoup d’échanges techniques ont eu lieu avec les participants. Sur la question des marchés publics, Parcs Canada et la Ville de Montréal ont mentionné qu’ils sont dans le même bateau et que pour eux il est difficile de procéder par devis de performance. Ils vont tenter d’intégrer la solution aluminium à un pilote, tout comme l’a fait et tentera à nouveau de le faire le MTQ à Metabetchouan – Lac-à-la-Croix dans un pont de même envergure que celui de St-Ambroise.
Greg Osberg a proposé que soit utilisé un modèle d’évaluation des soumissions qui permettrait d’évaluer le matériau au mérite. Voir le document Word intitulé Lightweight Bridge Deck RFP Template (non-proprietary) disponible sur le site web d’AluQuébec. Il a aussi suggéré que soient utilisées les études techniques d’autres juridictions comme une étude faite en Oregon (D. Evans), de même que le rapport comparatif du FDOT présenté plus haut.
La présentation technique qui suit s’est inspirée dans ses grandes lignes de l’ensemble de ces rapports et présentations audiovisuelles. Il convient de souligner que le rapport intitulé Ponts et Passerelles en Aluminium – Rapport de visites et de rencontres en Suède, en Hollande et aux États-Unis, aussi disponible sur le site d’AluQuébec, est tout à fait complémentaire au présent rapport, puisqu’il présente, entre autres, le compte rendu technique de la mission préparatoire aux États-Unis en février 2015. De l’information technique pertinente, qui ne sera pas nécessairement répétée dans le présent rapport, y est présentée.
Journée du 29 octobre, en après-midi
En après-midi, nous avons visité SeaCoast, l’entrepreneur chargé d’installer deux sections de platelage d’aluminium sur le tablier existant du pont mobile de Fort Pierce. Une section a été conçue à l’aide des extrusions de 5 pouces de profondeur et de 13 pouces de largeur, et l’autre a été fabriquée à l’aide des nouvelles extrusions améliorées de 18 pouces de largeur. Les deux sections avec leur revêtement de surface étaient déjà boulonnées aux poutres de support en acier galvanisé dans l’atelier lors de la visite.
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4- LES TRAVAUX D’ALUMABRIDGE ET DE SON ÉQUIPE
Alors qu’il travaillait pour SAPA à Connersville, en Indiana, Greg Osberg a utilisé l’extrusion de pont Alumadeck de 8 pouces (200 mm) de profondeur développé il y a plusieurs années par la Reynolds Metals pour produire des panneaux soudés pour platelage de ponts de façon standard. Un de ces platelages a été utilisé à titre expérimental pour le pont de St-Ambroise au Québec (figure 1).
Figure 1- Pré-assemblage des deux panneaux du tablier de 8 pouces du pont de St-Ambroise
Greg Osberg a démarré sa propre firme, AlumaBridge, et, en partenariat avec quelques collaborateurs, il a développé un nouveau profilé extrudé (de première génération) de 5 pouces (127 mm) de profondeur et de 13,624 pouces (346 mm) de largeur, calqué sur le modèle du profilé de 8 pouces, c’est-à-dire avec une paroi supérieure plus épaisse que la paroi inférieure (figure 2).
Figure 2 – Profilé de 5 pouces de profondeur et de 13 pouces de largeur, de première génération
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Ce profilé est plus adapté au remplacement des grillages métallique vieillissants de 5 pouces de profondeur que l’on retrouve sur des centaines de ponts mobiles aux États-Unis et en particulier en Floride. Un exemple de ces ponts est montré sur la figure 3.
Figure 3 – Exemple de pont mobile avec grillage en acier comme platelage
Les profilés de 8 et 5 pouces (première génération) sont extrudés par SAPA en Indiana et sont soudés par friction-malaxage à l’aide d’une toute nouvelle machine chez HF Webster de Rapid City, au Dakota du Sud (figure 4).
Figure 4 – Soudage par friction-malaxage d’un panneau de platelage de 5 pouces
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Le revêtement de type Flexolith (low modulus epoxy coating and broadcast overlay system) produit par Euclid Chemical à Cleveland, OH, (http://www.euclidchemical.com/) est ensuite appliqué par HRI Inc. à Williamsport, PA, (http://wwwhriinc.com/). La figure 5 montre un panneau sur lequel le revêtement de surface Flexolith vient d’être appliqué. Il existe une variété de couleurs et de textures d’agrégats pouvant être utilisées. Ce revêtement offre une excellente adhérence à l’aluminium et une très grande résistance au dérapage puisque son coefficient de friction est de l’ordre de 0,9.
Les panneaux ainsi fabriqués sont enfin expédiés sur les sites par camions (figure 6). Le panneau montré sur la figure 5 est le premier à être livré chez Seacost Inc. de Floride pour être installé et testé sur un pont de Fort Pierce, FL. La firme LBFoster développe le produit en partenariat avec AlumaBridge et en fait la promotion.
Plus récemment, Greg Osberg et son équipe ont développé un profilé extrudé de 5 pouces de deuxième génération, plus large et plus facile à souder par friction-malaxage, puisque le support envers est fourni par la section elle-même aux niveaux des parois horizontales. Ce profilé, montré sur la figure 7, a maintenant 18 pouces (457 mm) de largeur et possède des parois supérieures et inférieures d’égale épaisseur. Il permet une fabrication plus rapide des panneaux, ce qui abaisse le coût de production de 150$ à 119$US/pi2. Le profilé de deuxième génération est maintenant extrudé par Taber Extrusions de Russelville, Arkansas ou Gulfport, Mississippi.
Figure 5 – Panneau de tablier de 5 pouces avec revêtement Flexolith (époxy-granulats)
avant la livraison chez Seacoast
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Figure 6 – Nouvelle façon de faire : large extrusion, soudage par friction-malaxage
et livraison des panneaux sur les sites
Ce qui a conduit AlumaBridge à concevoir et produire un platelage de 5 pouces est un programme de recherche qui a été mis sur pied par le Florida Department of Transportation (FDOT) pour évaluer différentes options de platelage ou de tablier léger pour le remplacement des grillages d’acier vieillissants de leurs nombreux ponts mobiles (figure 8). C’est le platelage d’aluminium qui a finalement été retenu comme étant la meilleure option.
5- L’ÉTUDE COMPARATIVE DU FDOT
Les grillages d’acier, utilisés abondamment dans les années 50 à 70 comme platelage dans la plupart des ponts mobiles des États-Unis et surtout en Floride, ont démontré plusieurs lacunes au fil des ans. Le Florida Department of Transportation a donné le mandat à la firme URS Corporation Inc. de mener une étude permettant de comparer diverses alternatives de remplacement du grillage d’acier par des systèmes de platelage plus modernes, plus appropriés et, dans la mesure du possible, aussi légers que l’acier grillagé. Cette étude doit ultimement permettre d’identifier le système qui s’avèrera le plus avantageux sur la base de plusieurs critères.
Figure 7 – Profilé de 5 pouces de profondeur et de 18 pouces de largeur, de deuxième génération
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Figure 8 – Rapport du FDOT sur l’étude comparative de solutions de remplacement des grillages d’acier des
ponts mobiles de Floride par des platelages légers plus adaptés
Les systèmes de platelage sélectionnés sont :
1- le système de panneau sandwich (sandwich plate system, dit SPS) montré sur la figure 9; 2- le platelage orthotrope en aluminium (aluminum orthotropic deck) montré sur la figure 10; 3- le tablier composite en polymère renforcé de fibre de verre (fiberglass reinforced polymer (FRP)
composite deck), montré sur la figure 11; 4- le tablier de béton ultra-haute-performance (ultra-high performance concrete (UHPC) deck),
montré sur la figure 12.
Figure 9 - Système de panneau sandwich
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Figure 10 – Platelage orthotrope de 5 pouces en aluminium (alors en développement)
Figure 11 - Tablier composite en polymère renforcé de fibre de verre
Figure 12 - Tablier de béton ultra-haute-performance
On a donné au grillage d’acier une note moyenne de 500/1000 et on a comparé les quatre autres systèmes à ce dernier. Une note finale inférieure à 500 indique que le système considéré n’est pas plus avantageux que le grillage d’acier. Seuls les systèmes de platelage qui ont reçu une note de passage substantiellement supérieure à 500 sont susceptibles d’être retenus. Le Tableau détaillé, montré à la page 10 du rapport du FDOT, présente la grille d’évaluation de l’étude.
Les six principaux critères retenus sont le coût, la fonctionnalité et la sécurité, la maintenance, la durée de vie et la durabilité, la constructibilité et les autres risques. Le platelage orthotrope en aluminium est le seul qui s’est vraiment différencié avec une note de 557/1000 points. C’est ainsi qu’on a confié à
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George Patton la responsabilité de procéder à une étude plus poussée et à une série d’essais en laboratoire sur le système de platelage de 5 pouces avec la collaboration de Greg Osberg qui en était déjà le promoteur. Le tablier d’aluminium de 5 pouces a un poids tout à fait équivalent à celui du grillage d’acier, comme le confirme le Tableau des résultats obtenus par le FDOT. C’était un des principaux critères recherchés pour éviter d’avoir à intervenir au niveau des contrepoids. Le rapport de recherche du FDOT doit être lu par quiconque s’intéresse à l’utilisation de matériaux légers dans les ouvrages d’art. Il contient une mine d’informations susceptibles d’intéresser les décideurs dans leur choix de matériaux.
L’équipe de développement autour de G. Patton et de G. Osberg s’affaire présentement à valider expérimentalement, avec le support du FDOT, les résultats d’analyse obtenus par les études analytiques et numériques de G. Patton
6- PROGRAMMES DE DÉVELOPPEMENT, D’ANALYSE ET DE RECHERCHE
Puisque le système de tablier de pont avec platelage d’aluminium de 5 pouces de profondeur n’était pas entièrement conçu et fabriqué au moment de la rédaction et de la publication du rapport du FDOT, il a fallu mettre le pied sur l’accélérateur en termes de développement, d’analyse et d’essais de qualification du produit, lorsque ce dernier a été sélectionné.
Les premiers développements ont été faits autour du profilé de 5 pouces de première génération : conception et extrusion du profilé, soudage du platelage par friction-malaxage, pose du revêtement, analyses par éléments finis, analyse du diaphragme selon les recommandations d’AASHTO et réalisation du programme d’essais. Les travaux de conception, d’analyse et d’essais sont essentiellement sous la responsabilité de G. Patton. Les analyses sont, à toutes fins pratiques, terminées, même pour le profilé amélioré de deuxième génération, qui n’a été développé que tout récemment. Les figures 13 à 18 qui suivent montrent les différentes étapes de la fabrication du profilé de deuxième génération et du platelage qui en a résulté.
Figure 13 – Matrice et extrusion du profilé
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Figure 14 – Soudage par friction-malaxage des profilés extrudés
Figure 15 – Les trois extrusions de base du nouveau platelage
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Figure 16 – Vue en coupe du platelage montrant la possibilité d’ajustement des extrusions d’extrémité permettant d’obtenir la largeur de panneau voulue
Figure 17 – Montage des panneaux sur les poutres de support – boulonnage anti-glissement en atelier aux
poutres galvanisées secondaires et boulonnage sur l’âme des poutres transversales du pont
Figure 18 – Illustration du joint d’expansion entre deux panneaux de première génération
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Différents systèmes ont été analysés tant analytiquement que numériquement. Le système 1, par exemple, a permis l’évaluation de la flexion en considérant l’action composite du diaphragme disposé longitudinalement sur les poutres de support. Le système 2 a permis l’analyse de la flexion transversale positive, de la flexion négative et de la flexion du porte-à-faux, et le système 3, l’analyse des contraintes locales des parois. Les trois systèmes considérés sont illustrés sur la figure 19 et un résultat des analyses par éléments finis est présenté sur la figure 20.
Figure 19 – Les trois systèmes analysés
Figure 20 – Un des résultats des analyses par éléments finis démontrant le faible niveau des contraintes
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dans les parois du diaphragme
Le constructeur Seacoast a reçu un panneau de première génération au début de l’année 2015 et un panneau de deuxième génération à l’automne de la même année. Ces deux diaphragmes ont été boulonnées côte-à-côte sur les poutres de support, à temps pour la visite de la délégation dans l’après-midi du 29 octobre. Les figures 21 à 26 qui suivent montrent les détails du tablier orthotrope résultant.
Figure 21 – Vue d’ensemble des deux panneaux montés sur les poutres de support (le panneau de première génération est en avant-plan)
Figure 22 – Détails de l’extrémité du panneau de deuxième génération
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Figure 23 – Emplacement du joint d’expansion entre les deux panneaux
Figure 24 – Boulonnage du platelage à une poutre de support
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Figure 25– George Patton et Greg Osberg devant leur œuvre
Figure 26 – Équipement magnétique développé pour le positionnement des boulons
à l’intérieur des cavités du diaphragme
Les assemblages et le revêtement (phase 1; figure 28) et le tablier dans son ensemble (phase 2), subiront une série d’essais en laboratoire en Floride pour confirmer les résultats d’analyse obtenus par George Patton. Les deux générations de platelage seront ensuite installées et testées, à titre expérimental, sur un pont mobile de Fort Pierce (phase 3; figure 29). Il est possible que la phase 2 ne soit pas réalisée pour raccourcir la période de validation et parce que les concepteurs et le FDOT ont confiance que le produit devrait bien se comporter.
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Figure 27 – Montage expérimental pour les essais de cisaillement de l’assemblage boulonné (phase 1)
Figure 28 – Installation par Seacoast du platelage expérimental sur une section
d’un pont mobile de Fort Pierce, FL (phase 3)
Le platelage de première génération a été décrit dans le rapport de la mission préparatoire du mois de février 2015. Les caractéristiques des extrusions principales et d’extrémité y sont présentées, de même que l’installation du diaphragme, les assemblages, les joints d’expansion, le recouvrement et les dispositifs de retenue.
7- LE PONT DE ST-AMBROISE
Il convient de glisser quelques mots sur la première expérience du Ministère des Transports du Québec dans l’utilisation d’un platelage orthotrope en aluminium sur son territoire.
Pour valider le bon comportement d’un pont avec platelage d’aluminium dans les conditions climatique et d’utilisation du Québec, le MTQ a choisi de réhabiliter un petit pont dans la région du Saguenay (figure 29). AlumaBridge s’est qualifié pour la conception et la fabrication du platelage d’aluminium et un entrepreneur local s’est vu octroyer le mandat de procéder à la construction de la structure de support et à l’installation du platelage.
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Figure 29 – Pont de St-Ambroise au Saguenay
AlumaBridge a répondu à l’appel d’offre du MTQ, mais des délais sont survenus autant de la part du MTQ que d’AlumaBridge qui a vécu une série d’événements incontrôlables. Effectivement, la compagnie propriétaire de l’imposante machine à souder par friction-malaxage a dû démonter sa machine en mai 2014 et la déménager au Dakota du Sud, puisque son contrat de location dans des locaux de l’armée américaine n’a pu être renouvelé. Comble de malheur, elle a ensuite été victime d’une inondation de ses nouveaux locaux et il a fallu refaire la dalle de béton sur laquelle reposait la machine. De plus, la fabrication de matrices d’extrusion s’est avérée beaucoup plus longue que prévue.
En décembre 2014, AlumaBridge livre finalement les deux sections soudées du platelage d’aluminium au Saguenay (figure 30). Comme le MTQ avait décidé de faire installer le revêtement Bimagrip sur le site et non pas en usine, l’installation du platelage fut retardée à l’été 2015. Selon Greg Osberg, le revêtement Flexolith qu’il avait recommandé aurait dû être retenu et installé à l’usine, ce qui aurait pu permettre la mise en place du pont dès décembre 2014.
Figure 30 – Livraison des panneaux du pont de St-Ambroise
Chaque panneau a 32,9 pieds (10,04 m) de longueur et 12,3 pieds (3,75 m) de largeur. Le profilé de 8 pouces (203 mm) de profondeur utilisé (figure 31) est le premier modèle d’extrusion exploité par AlumaBridge. C’est en fait le profilé de la Reynolds Metals déjà utilisé, entre autres, dans le pont Corbin, PA, le pont de la Route 58, VA, et le pont Sandisfield, MA. Pour plus de détails sur ces ouvrages, le lecteur est invité à consulter le rapport de mission de février 2015 ainsi que la présentation de G. Osberg sur le site web d’AluQuébec. Il convient de souligner que les panneaux de 5 pouces de
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profondeur auraient pu aussi être utilisés pour ce pont. Ils n’étaient toutefois pas encore développés au moment de l’attribution du contrat.
Figure 31 – Trois extrusions de 8 pouces soudées par friction–malaxage et recouvertes du revêtement Flexolith
Les figures 32 à 36 montrent certaines étapes de la construction du pont de St-Ambroise et certaines particularités du platelage orthotrope utilisé. La présentation de G. Osberg présente un supplément d’information.
Figure 32 – Autres types d’extrusions utilisés pour la fabrication du platelage du pont de St-Ambroise
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Figure 33 – Dessins d’atelier du pont : 5 poutres de support, connexions du platelage aux poutres et glissières boulonnées au platelage
Figure 34– Installation du platelage sur la structure de support
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Figure 35– Moyen retenu pour connecter le platelage aux poutres - le perçage des ailes de poutres n’était pas autorisé
Figure 36 – Le pont de St-Ambroise en phase finale de construction
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CONCLUSION
Tous les participants à la rencontre de Tampa Bay, qu’ils soient américains, ontariens ou québécois, s’accordent à dire qu’elle s’est bien déroulée et qu’elle fut très instructive. Nous tenons à souligner la qualité des échanges et des informations fournies par nos hôtes américains. Ces derniers ont fait preuve d’une très grande ouverture à partager leurs technologies et leurs aspirations. Nous les en remercions très sincèrement. Il est à espérer que de nouveaux projets de réalisation et des alliances découleront de ces échanges à court et à moyen termes aussi bien au Canada qu’aux États-Unis.
Il est intéressant de constater que plusieurs participants et autres intervenants ont exprimé le désir de participer à un exercice semblable du côté de l’Europe dans un avenir rapproché. Les platelages et ponts en aluminium semblent réellement susciter de l’intérêt en Amérique du Nord.
Aluminum Bridge Decking
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• AlumaBridge Introduction
• Benefits of Aluminum Decking
• Product Features
• Deck Systems
• Bridges in Service
• Case Study
• Project Examples
• Extrusion Design
• Gen I 5” Deep Deck
• Gen II 5” Deep Deck Launch
• Supply Chain
• Bimetallic Corrosion
• Fire Resistance
• Research History
• Non-Proprietary Bid Template
• Q&A 2
Overview
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• AlumaBridge leading the way in design and supply of aluminum deck panels
• First deck of this type installed in 1996
• Patent protected and new patent pending
• Exclusive access to critical manufacturing assets
• L. B. Foster Fabricated Bridge Products – Exclusive North American Distributor
• Ideal alternative for:
– Structurally deficient bridges
– Functionally obsolete bridges
– Moveable bridges
– Historic bridges
Leadership in Aluminum Bridge Decking
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Solid Foundation & Well Positioned
• Successfully developed cutting-edge aluminum bridge technology
– Friction stir welding (FSW) introduced in 2012, optimized in 2015
• Aluminum bridge decking tested and in service
– 19 years of successful performance in U.S.
• AASHTO Code revisions to include aluminum were ratified in July 2012
• Growing interest in Canada
– Ministry of Transportation awards aluminum deck in Quebec
– Installation completed in July 2015
• Florida DOT selects aluminum decking to replace steel open grid
– Gen I 5” deep decking delivered in February 2015
– Gen II 5” deep decking delivered in October 2015
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FDOT Study Aluminum Decking to Replace Steel Open Grid
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• Lightweight structural aluminum to reduce dead-load
• Prefabricated for accelerated bridge construction
– Minimizes traffic interruptions and need for expensive traffic control
• Lower lifecycle costs
• Advantages over existing deck alternatives
– Corrosion resistant with minimal maintenance…no painting!
– Better skid resistance and less road surface noise compared to grid decks
– Capable of a 3.5’ cantilever on each side of bridge to widen roadway
• Can utilize existing superstructure
– Simple mechanical connections for fast installation and easy inspection
– Damaged deck panels can be quickly fabricated and replaced
Benefits of Solid Deck Aluminum Panels
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Aluminum Deck Features
• Weight: 21 - 23 lbs./sq. ft. (depending upon deck depth and wearing surface)
• Structural Efficiency
– Composite or non-composite behavior with steel beams
– Similar to monolithic concrete deck
– 90% as strong transversely as longitudinally
– Designed for infinite fatigue life using AASHTO Specifications
– Polymer concrete wearing surface performs well on highways
– Impacts from pneumatic tires not a concern
– Meets LRFD code
– Chemical and UV resistant
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• Maintenance Requirements
– No corroded surfaces to repair
– Wearing surface can be removed and applied in field (indefinitely sustainable)
• Constructability
– Meets goals for Accelerated Bridge Construction (ABC)
– Rapid deployment of lightweight panels
• Adaptability
– Decks in service with beam spacing up to 9’
– Potential to reuse beams
– Addresses functionally obsolete bridges (too narrow) with cantilever
Aluminum Deck Features
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• Wearing Surface
– 2-part epoxy wearing surface
– Variety of aggregate colors and textures
• Functionality and Safety
– Improved skid resistance (0.8 to 0.9 friction coefficient)
Aluminum Deck Features
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• Experience and Performance
– Decades of aluminum bridge applications and evolution
– 100-year deck technology may have been deployed 19 years ago
• Specifications
– AASHTO LRFD Section 7 Code incorporates aluminum
• Revisions ratified on July 9, 2012 by T-14 Steel Design Committee
– AWS D1.2 includes friction stir welding as of June 2014
– Meets Canadian Highway Bridge Design Code S6-06
Aluminum Deck Features
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8” Deep Deck Profile Replaces Concrete on Steel Girders
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WELDING ALUMINUM ORTHOTROPIC DECK
Corbin Bridge Huntingdon, PA
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Case Study
• Aluminum deck installed on the Corbin Bridge in Huntingdon, PA
• A historic bridge, so reconstruction was not an option
• Bridge posted for 7 tons before rehab
• Over 80,000 pounds of dead-load removed
• Load rated for 24 tons after rehab
• Performing well after 19 years of service
Before After
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- Bridge was functionally obsolete - Bridge was widened using existing substructure
U.S. Route 58 – Virginia
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Sandisfield, MA Bridge Completion & Shipment
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Sandisfield, MA Bridge Lifting & Positioning: 15 minutes
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Sandisfield, MA Bridge Placement on Bearings: 15 minutes
“From crane to bearings in 30 minutes!” 21
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Sandisfield, MA Bridge April 21, 2015
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• Deck Design Requirements:
– 8” (203.2 mm) deep deck
– Non-composite
– 2 large panels with a longitudinal splice joint
• Each panel 32.9’ (10,040 mm) x 12.3.’ (3,750 mm)
– Need method to attach guard railings to deck
– Cannot bolt deck to beams
• Need non-mechanical connection at base of longitudinal splice joint
• 4 unique extrusion dies had to be cut in Europe with a 10-week lead-time
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St. Ambroise River Bridge Quebec, Canada
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• May 2014: Fabricator’s contract for leased space in U.S. Army facility is cancelled
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St. Ambroise River Bridge Fabrication ‘One-Time’ Delays
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• Friction stir welding machine had to be disassembled and relocated
• Fabricator acquires new facility near current operation in Rapid City, SD
• New facility floods after record rainfall
• New concreate floor had to be poured for FSW machine
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St. Ambroise River Bridge Fabrication ‘One-Time’ Delays
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• May 2, 2014: Final shop drawings approved by MTQ and contractor
• August 11, 2014: First weld is made
– Two-sided FSW was necessary for Gen I profile design
– Two welding head passes to ensure full weld consolidation
– Some extrusions had be rerun and others roll corrected
• October 24, 2014 Fabrication and machining completed
– AlumaBridge included machining (hole drilling/countersinking) at no additional cost
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St. Ambroise River Bridge Fabrication ‘One-Time’ Delays
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• December 10, 2014: Panels ship from fabrication facility in Rapid City, SD
• January 15, 2015: Independent inspection completed in Quebec
– Friction stir weld and leak proof tests
• January 20, 2015: Ministry of Transportation – Quebec (MTQ) issues acceptance
• July 2015 installation
St. Ambroise River Bridge
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• 32.9’ (10,040 mm) x 24.6’ (7,500 mm) deck assembly (all within tolerance)
– Flatness Avg.: 0.37” (9.4 mm)
– Straightness: 0.21” (5.4 mm)
– Squareness: 0.167” (4.2 mm)
– Width: 0.125” (3.2 mm)
St. Ambroise River Bridge
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• Less than 5/16” (7.9mm) gap between deck and girder
• Deck is well within tolerance
• Beam camber unknown?
• Are bearing seats level?
• Installation process solution:
– Polyethylene sheet to provide bond breaker between girder and epoxy resin
– Aluminum deck and girder remain non-composite
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St. Ambroise River Bridge Installation
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• Ballast wall concrete prepared without clearance for corner guardrail fasteners
– Contractor drills holes for guardrail posts before realizing there is no clearance
• Installation process solution:
– Guard rails relocated slightly away from ballast wall for clearance
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St. Ambroise River Bridge Installation
No clearance
Improperly drilled holes
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• Water leak at splice joint
• Leak occurred before wearing surface/waterproof membrane applied
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St. Ambroise River Bridge Installation
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St. Ambroise River Bridge Polyurethane Wearing Surface/Waterproof Membrane
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Watertight Seal Along Splice
with Membrane
Mechanically Fastened Closure Plate
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St. Ambroise River Bridge New 8” Deck Extrusion Profiles
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St. Ambroise River Bridge Shop Drawings
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St. Ambroise River Bridge
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St. Ambroise River Bridge
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St. Ambroise River Bridge
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St. Ambroise River Bridge
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St. Ambroise River Bridge
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St. Ambroise River Bridge
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St. Ambroise River Bridge
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Gen I 5” (127 mm) Deep Deck Profile Replaces Grid Decks (Ideal for Movable Bridges)
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Movable Bridge Applications
• Improved safety
– Better skid resistance
– No ‘see through’ decks
– No car steering influences
– Quick installation
• Rehabilitation potential
• Reduced maintenance
• Enhanced longevity
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5” Deep Deck - Base Extrusion Profile 5” Deep Deck - End Extrusion Profile
• New 6063-T6 alloy chemical composition offers improved ductility and fatigue resistance
• End extrusion offers structural panel closure and width adjustability
– End extrusion legs can be trimmed back for panel width variance
• Three primary FSW tests for quality assurance (Ultrasonic testing can also be performed)
– Macro Analysis: Cut, polish and analyze weld core during pre-production trials
– Tensile Tests at start and stop of weld seams
– Force Analysis: Compares forces of welder for acceptable welds in trials to production welds
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5” Deep Deck Gen I
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Extrusion Production
• Extrusion trials confirm 50’ maximum length for 5” deep deck
• Extrusion trials confirm 33’ length required for 8” deep deck
– St. Ambroise River Bridge, Quebec
– Potential for longer length on new extrusion press
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FDOT Panel Fabrication Gen I 5” Deep Deck
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• Maximum panel length: 50’
• Maximum panel width: 14’ – Longer and wider available with transverse FSW or panel splice joints
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Wearing Surface Application Gen I 5” Deep Deck
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5” Deep Deck Gen I
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5” Deep Deck Gen I
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Gen II 5” Deep Deck (18”-Wide Profiles) Optimized for Friction Stir Welding Efficiency
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Gen II 5” Deep Deck (18”-Wide Profiles)
Deck Enhancements
Wider extrusions
Fewer welded joints
Single-sided FSW
More efficient than self-reacting (2-sided FSW)
Over 2x to 3x the welding speed with no weld flash
Faster setup times
Matched top and bottom flange thicknesses
Greater weld shrinkage control with 20% less heat
Verification of Refinements
Structurally equivalent to original deck product
Performance of new profiles
Manual calculations (section properties) – System 2
Transverse forces from loading between stringers
Finite element analysis – System 3
Localized flexure from wheel patch loading
Male - Female
Male - Male
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Gen II 5” Deep Deck Trimmable End Extrusion
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Very Low Stress at FSW Joint Re-Entrant Corners (Very Low Risk of Cracks at Stress Raisers)
Maximum Live Load Fatigue Stress Range < 0.5 x Constant Amplitude Fatigue Stress (Conservative Design)
Moving Wheel Patches FEA Model
FATIGUE STRESS RANGE RESULTS
Gen II Finite Element Analysis Results Conducted by Hardesty & Hanover
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Trimmable End Extrusion
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Gen II 5” Deep Deck Extrusion Dies
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Gen II 5” Deep Deck FDOT Panel Fabrication
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Gen II 5” Deep Deck FDOT Panel Fabrication
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Gen II 5” Deep Deck FDOT Panel Fabrication
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Gen II 5” Deep Deck FDOT Panel Fabrication
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• Facilitates alignment
• Minimizes field work
• Stringers clear floorbeam flange
• Typical existing bascule spacing 4.0’ to 4.5’
• Increased panel strength/stiffness provides opportunity to respace stringers
– Deflection: L/3,000
• 6.0’ span (optimal spacing for most bascules)
• 2.0’ cantilever (avoid support on main girders and floorbeams)
• Panel splices and/or expansion joints (WABO Evazote UV Seal – 1” Joint)
• ASTM A325 ¾” bolts
Shop Connection of Panels to Stringers Gen II 5” Deep Deck
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Manufacturing Supply Chain
• AlumaBridge has long-term exclusive manufacturing supply agreements
• Extrusion material specification with tight tolerances for friction stir welding
• New fabrication equipment for precision-welded deck panels
• Automation platform designed to meet market demand
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Aluminum-to-Steel with Zinc Coating
Electrical Potential Metal or alloy Potential (mV) silver -130 titanium -150 nickel -200 bronze -360 copper -360 steel -610 cadmium -700 aluminum (6063) -740 zinc -1130 magnesium -1600 Because the difference between aluminum’s potential (-740) and steel’s potential (-610) exceeds 100 mV, galvanic corrosion is possible when they are in contact. Since aluminum’s potential is less than steel’s, aluminum can be corroded by this contact, while the steel is protected.
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Corrosion Resistance 54-Year Aluminum-to-Steel Connection
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Fire Resistance
• 6063 structural aluminum alloy the same as used in mass transit trains
• Aluminum acts as a heat sink due to high thermal conductivity
– 4x greater than steel
• Dissipates heat from the flame source
• Absorbs more energy than steel from the center of the fire
• When aluminum melts it acts as flame retardant insulation
• Results in higher response time for fire fighters
• Mechanical strength of structural aluminum safe to 572 degrees
• Train floors achieved 19-minute fire resistance rating without fire barrier
– NFPA 130 and ASTM E 119 Standards
*Federal Transit Administration
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FHWA Sponsored Evaluations
• http://www.fhwa.dot.gov/publications/publicroads/97spring/alum.cfm
– FHWA article written by Bill Wright and published in Public Roads Magazine,1997 Spring Edition.
• http://www.virginiadot.org/vtrc/main/online_reports/pdf/99-r22.pdf
– Article written by the Virginia Transportation Research Council regarding tests performed on Little Buffalo Creek Bridge.
• http://www.virginiadot.org/VTRC/main/online_reports/pdf/00-r5.pdf
– Article on aluminum bridge deck built by Reynolds Metals Co. and written by VTRC.
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• Performance-based bid template
– No mention of aluminum
– Similar templates for Roadway Asset Management already in use
– Works well with design/build projects
• Avoids ‘sole-source’ concerns with proprietary/patented products
• Delivers ‘best value’ for bridge owners (technical proposal + price)
• Bid model reviewed and supported by FHWA
Lightweight Bridge Deck RFP Template
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• Gen II 5” Deep Deck Pricing: $119 (USD)/sq. ft.
– 21% price reduction from Gen I pricing of $150 (USD)/sq. ft.
– Assumes cost of aluminum at $.80/lb. – metal cost is a pass through
– Includes factory applied skid-resistant wearing surface
– Deck application engineering
– On-site consultation during deck installation
Pricing
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Next Steps?
www.alumabridge.com
AlumaBridge Video: http://www.alumabridge.com/alumabridge_video.htm
Q & A
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Contact Info
Mike Riley Marketing Manager
Construction Products – Bridge Group 415 Holiday Drive Pittsburgh, PA 15220 (412) 928-3452 Phone (724) 355-1878 Cell
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5-inch Aluminum Orthotropic Deck Research and Development
Florida Department of Transportation/AlumaBridge, LLC
Aluminum Bridge Deck Meeting
Tampa, FL October 29, 2015
Presented by: George Patton, PE
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FDOT Lightweight Solid Deck Research Project
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Purpose: Identify/Develop Viable Lightweight Deck System with Solid Surface to Replace Steel Open Grid Deck on Typical Florida Bascule Bridges
Weight Limitations on Existing Bridges
Trunnions, Main Girders 5-inch Aluminum Orthotropic Deck with FSW Joints Scored
Highest during Alternatives Screening Phase FRP, SPS, UHPC Waffle Slab also Considered 5-inch Depth not Originally Available Working with SAPA/AlumaBridge to Develop Derivative of Reynolds Alumadeck
5-inch Version Not Available - Project advanced to Deck System Development and Laboratory Testing Phase
Aluminum Orthotropic Deck
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Advantages:
Solid Surface (Functionality and Safety)
Weight Neutral Solution (21 - 22 psf)
Durability and Service Life Robust Design
Meets all AASHTO Limit States
High Stiffness
Corrosion Resistant
Fatigue Resistant (FSW Yields Improvements)
Configuration Adaptable to Different Bascule Configurations
Minimal Bridge Modifications
Accelerated Bridge Construction (ABC)
Aluminum Orthotropic Deck
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Advantages:
Available AASHTO LRFD Design Specifications
Material Familiarity and Predictability
Previous Testing and Research – 8-inch Deck Since 1936 (Smithfield Street Bridge, PA)
Derivative of Reynolds Alumadeck
FHWA/VDOT/VaTech Testing Program: 1995-1998
Previous Installations Rte. 58 over Little Buffalo Creek Bridge, VA
Sandisfield Bridge, MA
70+ Bridges in Europe
Aluminum Orthotropic Deck
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Disadvantages/Challenges: Relatively High Initial Cost
Initially $150/sf Now $120/sf (After Recent Refinements)
New Use of Product (Derivative) Coefficient of Thermal Expansion
12.8x10-6/F (Alum.) vs. 6.5x10-6/F (Steel) Panel Joints Recommended
Wearing Surface (Periodic Replacement) Galvanic Corrosion
Perception Issue Easily Addressed
Fasteners (Hollow Profile) Proprietary Product General Misconceptions
Aluminum Orthotropic Deck
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Extrusions 6063-T6 Aluminum Alloy
32-foot Max. Extrusion Lengths
5-inch Deep x 18-inch Wide Main Extrusions
5-inch Deep x 13 ½ -inch Wide End Extrusions
Ix = 60.76 in4/ft Sxb = 24.53 in3/ft Sxt = 24.08 in3/ft Ax = 15.11 in2/ft w = 18.4 psf
Male-Female Male-Male End
Aluminum Orthotropic Deck
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Extrusions Friction Stir Welded (FSW) to Create Panels
Infinite Range of Panel Widths Extrusions in Multiples of 4½” (18”, 13½” Main Extrusions)
End Extrusion Width Varies by 2¼” (Trim Flanges from 13 ½” to 11¼”)
Aluminum Orthotropic Deck
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5-inch Deck Spans Transversely across Stringers Typical Existing Bascule Spacing 4.0 to 4.5 feet
Increased Strength/Stiffness Provides Opportunity to Respace Stringers
6.0 feet Max. Recommended Span (Optimal Spacing for Most Bascules)
2.0 feet Max. Cantilever (Avoid Support on Main Girders and Floorbeams)
Aluminum Orthotropic Deck
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Accelerated Bridge Construction (ABC) Shop Bolt New Stringers to Deck Panels
Facilitate Alignment, Minimize Field Work
Stringers Clear Floorbeam Flange
WT Connection Stiffeners/Splice Type Connections
Friction Stir Welding (FSW)
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Renewed Interest in Aluminum Deck The Welding Institute, UK – 1991 Solid-State, Hot Shear Joining Process
Rigidly clamped plates Profiled pin plunges into material Shoulder in firm contact with surface Tool rotates rapidly and advances along joint Friction generates heat, softens material Produces plastic deformation and flow Material re-deposited from front to trailing edge Material forges into solid-state as it cools
Complex Thermo-Mechanical Process Varying temperature (0.7 to 0.9 melting point) Varying deformation Yields varying recrystallization Different zones and microstructures Translation and rotation yields asymmetric profile
Friction Stir Welding (FSW)
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Friction Stir Welding (FSW)
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Higher Quality Joint than previous Metal Inert Gas (MIG) Welding Significantly Less Heat Input with Lower Distortion and Residual Stress
Flaws still Possible: Voids, Lack of Fusion, Lack of Penetration, Faying Surface Defects, Presence of Entrapped Oxides
Quality Influenced by Tooling (Shoulder Size, Probe Size, Depth and Thread Details) Support (Alignment, Clamping Force) FSW Process (Rotation/Advancement Speed, Force, Inclination Angle)
Quality Control/Weld Inspection AWS D1.2 Structural Welding Code – Aluminum (2014) WPS, PQR, WPQR Bend and Macroetch Tests (Weld Tabs), Visual, RT/UT
Wearing Surface
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Euclid Flexolith (Low Modulus Epoxy Coating w/ Broadcast Overlay) - Recommended
Skid/Wear Resistance (Basalt/Alum. Oxide Aggregate Blend)
Two Layers (¼” Thickness, 3 to 4 psf Unit Weight)
Adhesion/Cohesion Bond Strength Environmental Factors (Temperature, Humidity)
Surface Preparation (Anchor Profile, Chemical Treatment, Cleaning)
Bond Strength Tests
Stiff Substrate permits Epoxy Polymer Binder
Resurfacing 10 to 15 Year Service Life Anticipated
17+ Year Service Life (Rte. 58 over Little Buffalo Creek, VA)
Resurface before Aluminum Substrate Exposed
Simplify Prep
Avoid Field Applied Chemical Treatment
Panel Joints
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Locate over Floorbeams and at Stringer Mid-Span
Reduce Thermal Forces (End Connection Moments)
Accommodate Panel Tolerances
WABO Evazote UV Seal (1” Joint) – FDOT Preference
Ultra Low Modulus Silicone Sealant (1/2” Joint)
Deck to Stringer Fasteners
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Treat Deck as Non-Composite for Stringer Design
Anticipate Composite Behavior for Connections (Slip Critical)
Class ‘B’ Surface Condition (Certified by RCSC) Abrasion Blast Aluminum Surface
Steel with Hot Dip Galvanized or Inorganic Zinc Primer Coatings
Proof Load (28 kips – ¾” Dia. ASTM A325 Bolt)
Design for No Slip from Live Load High Number of Cycles
Prevent Fretting (Premature Wear of Protective Coatings)
Prevent Bolt Fatigue (Reverse Bending)
Prevent Loosening from Vibration
Allow Slip from Thermal Load Low Number of Cycles
Forces Relieved after Slip Occurs
Conventional Fasteners - Recommended
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ASTM A325 Bolts (¾” Dia.) Heavy Hex
Tension Control Bolts
Hollow Profile Installation Challenges Requires Special Installation/Tightening Tools
Blind Type Fasteners – Not Recommended
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Böllhoff Rivnuts
Lindapter Hollo-Bolts
Not Recommended as Primary Fastener
Limited Bridge Applications (Used for Appurtenances)
Limited Pre-load Capability (Not used for Slip-critical)
Possible Loosening Under Vibrations
Possible Use for Maintenance Purposes
Fastener Design
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Compute Fastener Pitch for Composite Behavior (Live Load Shear Flow)
Discontinuity in Deck at Mid-Span Joint → “Spike” in Horizontal Shear Flow
Composite Section Properties Influenced by Shear Lag
Bottom Plate Fully Connected
Top Plate Attached to Bottom Plate through Inclined Webs
AASHTO LRFD Bridge Design Specifications
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Section 7 (Aluminum Structures) and Article 9.8.4 (Orthotropic Aluminum Decks) Analysis Similar to Orthotropic Steel Decks
Load Distribution Similar to Concrete Decks
Current Design Specifications Developed with Stiffening Ribs Parallel to Traffic
Additional Investigation Recommended for Stiffening Ribs Perpendicular to Traffic
Extensive FEA Program followed by Testing Program
HL-93 Design Truck and Tandem (Placement for Max. Effect) Maximum Positive, Negative, and Cantilever Negative Bending
Limit States Service I (Deflections)
Strength I
Strength II (Overload Permitting)
Fatigue I (Infinite Life)
Aluminum Orthotropic Deck Analysis
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System 1 Deck Longitudinal Forces (Axial and Flexure) from
Stringer Flexure with Composite Deck
System 2 Deck Transverse Forces (Flexure) from Loading
between Stringers
Positive, Negative and Cantilever Flexure
System 3 Localized Flexure of Deck from Wheel Patch Loading
Hollow Profiles behave as Rigid Frames
Aluminum Orthotropic Deck Analysis
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Load Distribution Equivalent Strip Width Equations
Wheel Distribution Similar to Concrete Decks
Simplified Analysis/Avoid FEA Each Time
Closed Form Equation – Compares Closely with FEA
Effective Slab Width, be = 0.5 x (26.0+6.6S) – Truck Wheel(s) at Edge of Panel Controls
Combined Effects System 2 (Global Flexure) x Shear Lag Multiplier + System 3 (Local Wheel Patch)
System 1 (Composite Flexure) + System 3 (Local Wheel Patch)
Shear Lag Effects Not Addressed in AASHTO LRFD
Multiplier from FEA
20% Increase in System 2 Stress (Top of Panel)
10% Increase in System 2 Stress (Bottom of Panel)
Aluminum Orthotropic Deck Analysis
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Deck Top Stress (Positive Moment – Tandem Loading) Section thru between Stringers
10” x 20” Unit 10 kip
Wheel Patch
System 2 – Load Distribution – 3D Plate and Shell FEA
6’-0” 6’-0” 2’-0” Stringer Spacing
Dir
ecti
on
of
Traf
fic
Panel Joint
Panel Joint
Deck Span
Aluminum Orthotropic Deck Analysis
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System 2 – Load Distribution – 3D Plate and Shell FEA
Deck Top Stress (Positive Moment – Truck Loading) Section thru Deck between Stringers
Direction of Traffic
Loca
l Eff
ect
Pan
el E
dge
Pan
el E
dge
Shear Lag
Aluminum Orthotropic Deck Analysis
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SYSTEM 2 POSITIVE FLEXURE MAXIMUM STRESSES AND DEFLECTIONS
Limit State
Loading
Max. Stress (ksi) Max. Deflection
(in) Tension (Bottom) Compression (Top)
Service I
HL-93 Design Truck 6.3 6.7 0.090
HL-93 Design Tandem 5.6 5.7 0.082
Strength I
HL-93 Design Truck 11.1 11.7 0.158
HL-93 Design Tandem 9.7 10.0 0.144
Strength II FL-120 Permit Truck 14.3 15.0 0.203
Limits ФfFnb = 27.5 25.2 0.090
SYSTEM 2 NEGATIVE FLEXURE MAXIMUM STRESSES AND DEFLECTIONS
Limit State
Loading
Max. Stress (ksi) Max. Deflection
(in) Tension (Top) Compression (Bottom)
Service I
HL-93 Design Truck 6.3 8.7 0.069
HL-93 Design Tandem 5.0 6.8 0.056
Strength I
HL-93 Design Truck 11.0 15.1 0.121
HL-93 Design Tandem 8.7 11.9 0.097
Strength II FL-120 Permit Truck 14.2 19.5 0.156
Limits ФfFnb = 25.2 27.5 0.090
SYSTEM 2 CANTILEVER NEGATIVE FLEXURE MAXIMUM STRESSES AND DEFLECTIONS
Limit State
Loading
Max. Stress (ksi) Max. Deflection
(in) Tension (Top) Compression (Bottom)
Service I
HL-93 Design Truck 5.7 8.1 0.107
HL-93 Design Tandem 4.6 6.8 0.097
Strength I
HL-93 Design Truck 10.0 14.3 0.187
HL-93 Design Tandem 8.1 11.9 0.169
Strength II FL-120 Permit Truck 12.9 18.3 0.241
Limits ФfFnb = 25.2 27.5 --
Aluminum Orthotropic Deck Analysis
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Design for Infinite Fatigue Life
Fatigue Sensitive Details Base Metal: Cat. ‘A’
FSW Joint (Stress Normal to Weld Axis): Cat. ‘C’
Consistent with CJP Welds Ground Smooth
Conservative Approach Based on MIG Welding
Testing - FSW Joints → Greater Fatigue Resistance than Base Metal
Conservative Design Design Nominal Fatigue Resistance =
½ x Constant Amplitude Fatigue Threshold
(ΔF)N=½(ΔF)TH
SYSTEM 3 - FATIGUE LIFE VALUES
Variable Category ‘A’ Category ‘C’
(ΔF)TH 9.5 ksi 4.0 ksi
Design (ΔF)N=½(ΔF)TH 4.75 ksi 2.0 ksi
ϒ (Δf) ≤ (ΔF)N 4.35 ksi 1.95 ksi
Aluminum Orthotropic Deck Analysis
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System 3 – Fatigue
3D Solid Element FEA
Stress Range from Moving Wheel Patch
General Corrosion
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6063-T6 Alloy – Excellent Corrosion Resistance Tightly Bonded Aluminum Oxide Film
Experiences Superficial Pitting Maximum Pit Depth is Fraction of Material Thickness
Avoid Standing Water Wetness from Condensation - Limited Duration
Rainwater Runoff through Joints/Edges
Seal Openings in Hollow Extrusions vs. Drain Holes
Experience FDOT, et al - Significant Experience with Galvanized
Fasteners in Marine Environments with No Significant Issues
Railings, Sidewalk Planking, Light Poles
Galvanic Corrosion
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Dissimilar Metals (Galvanic Series)
Less Noble (Anodic) Material Sacrifices to Protect More Noble (Cathodic) Material
Galvanized Steel Bolts/Stringers Zinc Less Noble than Aluminum
Zinc Sacrifices to Protect Aluminum
Maximize Zinc with Hot Dip or Mechanically Galvanized Coatings
After Zinc Material Spent Uncoated Steel is More Noble
Aluminum Deck Corrodes but is Negligible
Surface Area of Cathodic Material (Bolts/Stringers) Significantly Less than Surface Area of Anodic Material (Aluminum Deck)
Test Program - Goals
29
Deck System Performance per AASHTO LRFD Design Provisions
Compare Measured Stresses and Deflections to FEA
Applicability of AASHTO LRFD Equivalent Strip Width Equations Load Distribution
Required Adjustments for Shear Lag Effects
Combined System 2 and System 3 Effects
Fastener Performance/Design Parameters
Performance of Wearing Surface
Test Program – Phase 1 (Component Testing)
30
Verify FEA Results
Deck Panel Performance (Static)
Connection Testing
Constructability
Test Program – Future Phases
31
Phase 2 (Full System Testing) Skip Phase to “Fast Track” Test Program
Significant Confidence in Deck System
Phase 3 (Field Testing) Install Test Panels on Existing Bascule Bridge
Reuse Panels from Laboratory Testing
One Floorbeam Bay, Half Roadway Width
Latest Developments
32
5-inch Deep Deck Refinements Wider Extrusions (Reduced Number of Welded Joints)
Single Sided FSW Joints (More Efficient FSW)
Matched Top and Bottom Flange Thickness at Welded Joints (More Efficient FSW)
Verification of Refinements Structurally Equivalent to Previous Research
Performance of New Details
Finite Element Analysis – System 3
Manual Calculations (Section Properties) – System 2
Latest Developments
33
Finite Element Analysis (FEA) Results
Very Low Stress at FSW Joint Re-entrant Corners (Very Low Risk of Cracks at Stress Raisers)
Maximum Live Load Fatigue Stress Range < 0.5 x Constant Amplitude Fatigue Stress (Conservative Design)
Moving Wheel Patches FEA Model
FATIGUE STRESS RANGE RESULTS
Questions/Discussion?
BASCULE BRIDGE LIGHTWEIGHT SOLID DECK RETROFIT RESEARCH PROJECT
DECK ALTERNATIVE SCREENING REPORT
FINAL
FPID 419497‐1‐B2‐01
Prepared for:
Florida Department of Transportation Structures Design Office
Prepared by:
URS Corporation, Inc. 7650 West Courtney Campbell Causeway, Suite 700
Tampa, Florida 33607
May 14, 2012
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TABLE OF CONTENTS
1.0 INTRODUCTION AND EXECUTIVE SUMMARY ................................................................................... 1
1.1 PROJECT NEED ............................................................................................................................... 1
1.2 DECK SELECTION FACTORS ............................................................................................................ 2
1.2.1 General .................................................................................................................................. 2
1.2.2 Weight Considerations .......................................................................................................... 3
1.2.3 Deck Thickness Considerations ............................................................................................. 5
1.2.4 Deck Attachment Considerations ......................................................................................... 6
1.2.5 Bascule Leaf Framing System Considerations ....................................................................... 6
1.2.6 Constructability Considerations ............................................................................................ 7
1.2.7 Design Considerations ........................................................................................................... 8
1.2.8 Financial and Technical Support Considerations .................................................................. 8
1.2.9 Maintenance and Durability Considerations ........................................................................ 8
1.3 LIGHTWEIGHT SOLID DECK SYSTEM EVALUATION ........................................................................ 9
1.3.1 Evaluated Deck Systems ........................................................................................................ 9
1.3.2 Evaluation Process ................................................................................................................ 9
1.3.3 Evaluation Findings ............................................................................................................. 11
2.0 OVERVIEW OF EVALUATED LIGHTWEIGHT SOLID DECK SYSTEMS ................................................. 18
2.1 SANDWICH PLATE SYSTEM (SPS) DECK ....................................................................................... 18
2.1.1 Description .......................................................................................................................... 18
2.1.2 Product Development and Corporate Information ............................................................ 20
2.1.3 Constructability ................................................................................................................... 20
2.1.4 Functionality and Safety...................................................................................................... 22
2.1.5 Design and Analysis ............................................................................................................. 23
2.1.6 Durability and Service Life ................................................................................................... 27
2.1.7 Maintenance ....................................................................................................................... 29
2.1.8 Research .............................................................................................................................. 30
2.1.9 Recent Bridge Installations ................................................................................................. 30
2.1.10 Florida Bascule Bridge Specific Solution ............................................................................. 33
2.1.11 Costs .................................................................................................................................... 37
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2.1.12 References .......................................................................................................................... 38
2.2 ALUMINUM ORTHOTROPIC DECK ............................................................................................... 40
2.2.1 Description .......................................................................................................................... 40
2.2.2 Product Development and Corporate Information ............................................................ 41
2.2.3 Recent Bridge Installations ................................................................................................. 44
2.2.4 Florida Bascule Bridge Specific Solution ............................................................................. 46
2.2.5 Functionality and Safety...................................................................................................... 51
2.2.6 Durability and Service Life ................................................................................................... 51
2.2.7 Design and Analysis ............................................................................................................. 55
2.2.8 Constructability ................................................................................................................... 55
2.2.9 Costs .................................................................................................................................... 56
2.2.10 References .......................................................................................................................... 58
2.3. FIBERGLASS REINFORCED POLYMER (FRP) COMPOSITE DECK ................................................... 59
2.3.1 Description .......................................................................................................................... 59
2.3.2 Product Development and Corporate Information ............................................................ 60
2.3.3 Recent Bridge Installations ................................................................................................. 61
2.3.4 Design and Analysis ............................................................................................................. 66
2.3.5 Functionality and Safety...................................................................................................... 69
2.3.6 Durability and Service Life ................................................................................................... 70
2.3.7 Florida Bascule Bridge Specific Solution ............................................................................. 77
2.3.8 Constructability ................................................................................................................... 80
2.3.9 Costs .................................................................................................................................... 81
2.3.10 References .......................................................................................................................... 83
2.4 ULTRA‐HIGH PERFORMANCE CONCRETE (UHPC) DECK .............................................................. 85
2.4.1 Description .......................................................................................................................... 85
2.4.2 Product Development and Corporate Information ............................................................ 88
2.4.3 Recent Bridge Installations ................................................................................................. 88
2.4.4 Florida Bascule Bridge Specific Solution ............................................................................. 89
2.4.5 Functionality and Safety...................................................................................................... 91
2.4.6 Durability and Service Life ................................................................................................... 92
2.4.7 Maintenance ....................................................................................................................... 93
2.4.8 Design .................................................................................................................................. 94
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2.4.9 Research .............................................................................................................................. 94
2.4.10 Constructability ................................................................................................................... 94
2.4.11 Costs .................................................................................................................................... 95
2.4.12 References ........................................................................................................................ 101
3.0 WEARING SURFACE EVALUATION ................................................................................................. 102
3.1 INTRODUCTION ......................................................................................................................... 102
3.2 ALTERNATIVE WEARING SURFACES .......................................................................................... 103
3.3 THIN POLYMER OVERLAY WEARING SURFACES ....................................................................... 104
3.4 HOT SPRAY APPLIED METAL OVERLAYS .................................................................................... 106
3.5 DECK OVERLAY PROPERTIES ..................................................................................................... 108
3.6 REFERENCES .............................................................................................................................. 111
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1.0 INTRODUCTION AND EXECUTIVE SUMMARY
1.1 PROJECT NEED
The deck on the majority of bascule bridges in Florida consist of steel open grid roadway flooring, except
for the portion of deck over the machinery room, which consists of concrete filled steel grid roadway
flooring to protect the operating equipment below. The original decision to use steel open grid deck
was primarily to reduce weight and thus reduce load on the structure and operating equipment with
corresponding cost savings. At the time the majority of these bridges were constructed (from the mid
1950’s through the early 1970’s) steel open grid deck was considered the only available and practical
lightweight deck system.
However, steel open grid deck has been problematic for a number of reasons including:
Openings in the deck permit dirt and debris to collect on the steel framing members below. The
dirt and debris retains moisture that contains chlorides from the saltwater environment, which
is conducive to corrosion development. The network of steel grid bars makes cleaning of the
steel framing members difficult.
Although the deck typically includes a serrated top surface to improve skid resistance, the top
surface polishes over time from contact with wheels, which eventually reduces the skid
resistance, especially when wet, and reduces safety.
The welded fabrication of the steel open grid deck includes numerous fatigue sensitive details
(Category E Details per AASHTO LRFD) that are prone to fatigue development and as such the
deck design is typically governed by fatigue provisions. Bridges with heavier truck traffic have
commonly experienced premature fatigue cracking and localized failure of the secondary and
tertiary bars that result in larger holes in the deck.
Fabrication tolerances of both the steel open grid deck and bascule leaf steel framing have
resulted in difficulties in achieving uniform bearing of the deck main bars on the supports.
Excessive root openings and poor field welding practices have resulted in widespread cracking of
the deck attachment welds.
Tires in contact with the network of steel open grid bars and corresponding openings between
the bars create resonant vibrations that generate noise that is considered a nuisance to
residences and businesses nearby these bascule bridges.
The relatively large openings in the deck and the slippery surfaces make crossing the bascule
span on a bicycle a challenge. The bicycling community considers steel open grid deck a safety
concern.
Over the past 60 years, the Florida Department of Transportation has invested considerable resources in
addressing the above concerns including frequent repairs and replacement of the decks, and research
and development to address the safety and functionality concerns including methods to improve skid
resistance, wheel paths to reduce noise, and implementation of bicycle friendly surfaces in the shoulder
areas.
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The Department has recognized for many years that a deck with a solid surface solves most if not all of
these issues. Most new bascule bridges in Florida, constructed since 1999, have included a lightweight
solid deck with a concrete riding surface. There have been a number of deck systems classified as
lightweight solid deck systems that have been used on new bascule bridges throughout the United
States and abroad including:
Conventionally Reinforced Concrete Slabs using Lightweight Concrete,
Concrete Filled Steel Grid Deck (a.k.a. Grid Reinforced Concrete) using Lightweight Concrete,
Exodermic Deck using Lightweight Concrete,
Steel Orthotropic Deck.
However, because the weight of these deck systems is significantly greater than those of steel open grid
deck and there are limitations in the amount of weight that can be added to an existing bascule bridge,
it is not practical to use these deck systems to retrofit existing bascule bridges. Therefore these deck
systems were not evaluated in this study.
1.2 DECK SELECTION FACTORS
1.2.1 General
There are a number of factors that should be considered in the selection of a lightweight solid deck
system to replace steel open grid deck on typical Florida bascule bridges. These factors include:
Costs including:
o Deck fabrication and installation,
o Modifications to the bascule leaf steel framing, bascule pier, flanking spans,
counterweight, and trunnion assemblies required to implement the new deck system,
o Design and construction inspection for the new deck system,
o Future maintenance and inspection.
Functionality and Safety including:
o Load capacity (i.e. support of legal loads and permitted overloads),
o Improved riding surface and skid resistance for vehicular and bicycle traffic,
o Reduced traffic generated noise.
Maintenance including:
o Ease of repair and/or replacement of all or portions of the deck,
o Need for periodic maintenance (e.g. reapplication of coatings and/or replacement of
wearing surfaces).
Service‐life and Durability including:
o Deck and/or deck component (e.g. wearing service, fasteners, etc.) service‐life,
o Resistance to corrosion, fatigue, wear, impact, fire, ultraviolet light, and chemicals,
o Accommodation of thermal movements.
Constructability including:
o Disruption to traffic (e.g. overall construction duration, maintenance of traffic),
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o Ability to accommodate fabrication and installation tolerances,
o Sensitivity to environmental conditions during construction,
o Shipping, storage and handling,
o Specialized inspection requirements during fabrication and installation.
Other Risks including:
o Familiarity of the product and technology (e.g. years’ experience, previous bridge
installations, quantity and quality of applicable research, endorsement by bridge design
community and AASHTO ),
o Availability of design tools and construction techniques,
o Financial and technical support from supplier(s),
o Product availability (e.g. opportunities for competitive bidding, sole source and/or
patents).
1.2.2 Weight Considerations
In addition to the above factors, it is critical that the weight of a lightweight solid deck system including
all associated appurtenances, wearing surfaces, and modifications to the bascule leaf required to
implement the new deck, be as close as possible to that of the existing steel open grid deck that it will
replace. Because a bascule leaf is typically balanced to reduce the power required to operate the
bridge, weight added to the bascule leaf forward of the trunnions (i.e. forward of the pivot point)
requires corresponding weight in the counterweight to yield a balanced condition. Furthermore,
because the length of the counterweight is significantly shorter than the length of the bascule leaf, the
weight added to the counterweight is typically two to three times the weight added forward of the
trunnion.
Steel open grid deck found on most Florida bascule bridges consists of standard duty, hot dip galvanized,
diagonal roadway flooring (a.k.a. 5‐Inch 4‐Way Decks with main and secondary bars in an orthogonal
configuration, and tertiary bars in a diagonal configuration) with a unit weight of approximately 21
(pounds per square foot). The steel open grid deck used when the bridges were first constructed from
the mid 1950’s through the early 1970’s typically consisted of painted rectangular grid decks (i.e. main,
secondary and tertiary bars in an orthogonal configuration) with a unit weight of approximately 18 psf.
Additional ballast was added to the counterweights when these decks were replaced. Many additional
repairs and modifications have typically been performed on these bridges since they were originally
constructed that has increased the weight of the bascule leaves. These repairs and modifications have
typically included addition of steel reinforcing plates, replacement of structural members with new
heavier members, replacement of span lock assemblies with new heavier duty equipment and access
platforms, modifications to the bridge railings for safety purposes, addition of strips of concrete to the
steel open grid deck in the wheel lines to reduce traffic generated noise, et al and corresponding
addition of ballast to balance the span. Some attempts to offset the increased weight have been made
including the use of lighter weight aluminum components, where practical.
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There are a number of factors that limit the amount of weight that can be added to existing Florida
bascule bridges including limited trunnion capacity, space to accommodate additional counterweight
ballast, and structural capacity of the main girders.
The trunnion assemblies found on most existing Florida bascule bridges were originally designed for
lighter loads and have little or no reserve capacity. As such, increased bascule leaf weight is anticipated
to overload the trunnion assemblies, which will reduce the service life and/or result in premature failure
of trunnion assembly components. Increasing the loads on the trunnions beyond recommended limits is
not recommended because of anticipated:
Accelerated wear of the bronze bushings,
Increased structural deformation of the trunnion shafts and trunnion girders that affects
trunnion alignment with corresponding edge loading of the shaft journals on the bearing
bushings,
Higher fatigue stresses,
Significant vehicular and navigation traffic impacts, costs, and technical challenges to remove
and replace the trunnion assemblies.
Factors that limit the amount of ballast that can be added to the counterweights on most Florida
bascule bridges include:
Limited space in the counterweight adjustment pockets,
Limited clearance between the top of the counterweight and underside of the bascule pier or
flanking span deck with the bascule leaf in the lowered position,
Limited clearance between the underside of the counterweight and the machinery platform and
operating equipment with the bascule leaf in the raised position,
Limited space and technical challenges with mounting ballast to the rear counterweight girder,
Limited structural capacity of the bascule leaf main girders.
There are means to offset the increase in weight of a heavier deck system by replacing other elements
of the bridge with lighter components (e.g. replacement of the steel sidewalk grating, sidewalk support
members, bridge railings, and curb assemblies with lighter aluminum or fiber reinforced plastic (FRP)
members.) However, this strategy involves replacement of members that do not otherwise require
replacement and thus adds additional work and cost, and should generally be avoided where practical.
Because a portion of the existing bascule leaf deck consists of 3‐inch deep concrete filled steel grid deck
with a typical unit weight of approximately 50 psf, there are opportunities to reduce weight be also
replacing this portion of deck with the lightweight solid deck system when the steel open grid deck is
replaced. However, because the concrete filled steel grid deck is near the trunnion assemblies, there is
not a significant corresponding reduction in the amount of ballast in the counterweight with this
replacement.
Considering all of the above limitations and potential offsets, the maximum unit weight for lightweight
solid deck system that can be accommodated is approximately 25 psf.
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It may be possible to offset the increase in weight of a lightweight solid deck system by taking advantage
of improved structural efficiency including greater strength, stiffness, structural continuity, and/or
composite behavior of the new deck system to eliminate or reduce the number and/or size of existing
stringers supporting the deck. However, this may require additional modifications to the bascule leaf
steel framing system, bascule piers and/or flanking span structure that may not otherwise be required.
1.2.3 Deck Thickness Considerations
Proposed lightweight solid decks may have thicknesses that are different than the thicknesses of existing
5‐3/16” deep steel open grid deck and/or 3” deep concrete filled steel grid deck found on typical
existing Florida bascule bridges. The steel grid deck is typically supported directly on the rolled steel
stringers and on steel spacer bars on the main girders, floorbeams and forward counterweight girder.
On some Florida bascule bridges with Hopkins frame drive systems, the existing concrete filled steel grid
deck is also supported directly on the rack girders.
The difference in thickness between the new lightweight solid deck system and existing steel grid deck
must be addressed in the detailing of the deck support members. Lightweight solid deck systems with a
thickness similar to that of the existing steel grid deck will require fewer modifications to the existing
bascule leaf framing system.
Lightweight solid deck systems with a thickness greater than the existing steel open grid deck will result
in a roadway surface that is higher than the existing roadway surface. Modifications required to raise
the roadway surface on the bascule pier and/or flanking span deck surface to match that on the bascule
leaves will be significant including:
Adjustment of the approach span deck profile to match the raised deck on the bascule leaf by
lifting the end at the bascule pier by installing a fill at the flanking beam floorbeam bearings,
Replacement of the bascule pier sidewalk or raising of the sidewalk by pouring a new sidewalk
slab on top of the existing sidewalk slab,
Raising the bascule leaf sidewalk by replacing the sidewalk support framing, curbs, sidewalk
grating, pedestrian railings, and span lock access hatches,
Raising the control house floor and doors, flooring, floor hatches, ladders, plumbing, control
desk, electrical penetrations, etc.
Because of the magnitude of the required modifications, raising the roadway surface should be avoided.
Lightweight solid deck systems with a thickness less than the existing steel open gird deck will require
details that make up the difference between the top of the bascule leaf steel framing members
(stringers, main girders, floorbeams and forward counterweight girder) and the underside of the deck.
This can include setting the top of the stringers at a higher position. However, because it is generally
not practical to modify the height of the top flange of the main girders, floorbeams and/or forward
counterweight girder, it will be necessary to develop alternative details that allow for support and
attachment to the top flanges at these locations or additional members that permits support of the deck
that avoids support on these members.
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1.2.4 Deck Attachment Considerations
Each lightweight solid deck system uses a different method for attaching the deck to the bascule leaf
steel framing. A number of factors should be considered in attaching the deck to the bascule leaf steel
framing including the following:
Existing steel grid deck is typically field welded to the top of the steel stringers and spacer bars
on the main girders, floorbeams and forward counterweight girder and the current bascule leaf
steel framing details are geared toward these welded attachments that may not be conducive to
the attachment of alternative deck systems.
The solid deck surface may make attachment of the deck from the top side difficult or
impractical and thus the details may need to include access from below.
Details vary from bridge to bridge (e.g. riveted built‐up construction or welded built‐up
construction of the main girders, floorbeams, and forward counterweight girder) that can affect
the attachment details.
Differences in coefficients of thermal expansion between the deck material and the steel
bascule leaf framing may require the need for provisions to accommodate associated thermal
movements if restraint forces are determined to be excessive.
Tolerances in steel fabrication and erection may result in non‐uniform support conditions that
need to be addressed in the connections.
Use of dissimilar metals can produce conditions conducive for galvanic corrosion and thus it
may be necessary to implement measures to mitigate this concern including strategic selection
of materials and separation of dissimilar metals.
1.2.5 Bascule Leaf Framing System Considerations
Although there are similarities in the structural configuration of typical Florida bascule bridges, there are
also a number of variations in the configuration. The lightweight solid deck system must be able to
accommodate a wide range of dimensions and possible configurations using standard details.
The steel framing system for typical Florida bascule bridges all include a framework of:
Two (2) longitudinal main girders,
Multiple, parallel, transverse floorbeams that span between the main girders,
Multiple, parallel, longitudinal steel stringers located between the main girders and that span
between the floorbeams,
Steel grid deck (5‐3/16” deep steel open grid deck and 3” deep concrete filled steel grid deck
over the machinery room) that spans transversely, extends from outboard edge to outboard
edge of main girders, and is supported on the top of rolled steel stringers, and spacer bars on
the top flange of the main girders, and floorbeams,
Transversely level roadway surface with no cross slope or crown.
However, numerous differences can exist from bridge to bridge including:
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Two (2) travel lanes with a clear roadway width of 26 feet to 32 feet between curbs and with no
traffic separator, or four (4) travel lanes with a clear roadway width of 42 feet to 48 feet
between curbs with a mountable traffic separator (raised median),
Double‐leaf or single‐leaf configuration,
One or two sidewalks that are either raised or at the same level behind curbs,
Five (5) or six (6) floorbeams (including the forward counterweight girder) spaced from 15 feet
to 20 feet on center,
Varying number of stringers spaced from 4 feet to 4.5 feet on center,
Curbs that separate the roadway from the sidewalk either located outboard the steel grid deck
or attached to the top of the grid deck over the main girders.
Although the majority of older typical Florida bascule bridges do not currently include crash‐tested
traffic railings that separate the roadway from the sidewalk, the Department has a program to
incorporate these traffic railings were practical and where warranted. In most configurations, the traffic
railing would be mounted to the bascule leaf steel framing outboard the main girders and not mounted
to the bascule leaf deck. However, there may be isolated conditions where it may be necessary to
mount the crash‐tested traffic railing to the deck including temporary traffic railings for future traffic
control purposes. As such, the lightweight solid deck system must be able to accommodate mounting of
a crash‐tested traffic railing and to resist the vehicular impact loads transferred to the deck without
damage.
Roadway drainage of the solid surface is not considered to be a concern with transversely level roadway
surface. As such, the introduction of a roadway cross slope and/or crown is not recommended. The
bascule span is typically located at or near the peak of the roadway vertical profile and as such the area
of bridge deck that collects the stormwater is limited. The longitudinal profile grade will act to channel
stormwater off of the bascule span.
1.2.6 Constructability Considerations
Most existing Florida bascule bridges are located in urban areas with relatively high volumes of vehicular
traffic and over active navigation channels that require frequent bridge operation. Bascule leaf deck
replacement can have significant impacts on the traveling public. The modular configuration of steel
open grid deck has typically permitted rapid replacement of the deck, and associated stringers where
required, with minimal disruptions to traffic, using:
Short duration nighttime bridge closures, when traffic volumes are low, and restoration of
vehicular traffic during daytime periods, or
Phased construction with replacement of half of the deck at a time while vehicular traffic is
maintained on the bridge.
Lightweight solid deck systems should be able to accommodate replacement in a similar manner with
either of the above construction approaches where required to reduce traffic impacts.
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Lightweight solid deck fabrication and erection tolerances (e.g. flatness, squareness, sweep, camber,
length, width, thickness, etc.) should permit proper alignment and fit‐up of the deck without
unnecessary field modifications, construction delays, or poor final workmanship. Construction
requirements should generally avoid or minimize the need for specialized shop and/or field inspection
equipment and personnel, although critical deck material and physical properties should be verifiable by
testing. Quality of the field installation should not be sensitive to environmental conditions. The
lightweight solid deck system should have the capability to be field installed by typical bridge
rehabilitation contractors.
1.2.7 Design Considerations
Design methodology used to confirm the lightweight solid deck design should be relatively simple,
straightforward, and easily understood by qualified design professionals. Calculations to verify the deck
design and load rating should generally be based on conservative, simple closed‐form equations and not
sophisticated, in‐depth finite element analysis. Design methodology should be endorsed by AASHTO
and included in the AASHTO LRFD Bridge Design Specifications for use in consistent application by the
bridge design community.
It is preferred that the lightweight solid deck technology is generally familiar to the bridge design
community, has a significant positive track record in similar applications, and is supported by applicable
sound and reliable research and testing.
1.2.8 Financial and Technical Support Considerations
It is preferred that the lightweight solid deck system be a non‐proprietary product, with opportunity for
competitive bidding, and without royalty payments. Where the lightweight solid deck system is
proprietary, without similar competitive products, the deck supplier should have sufficient financial
support to ensure that the product is available in the future and that there is corresponding technical
support.
1.2.9 Maintenance and Durability Considerations
The lightweight solid deck primary structural system should be durable with a service life with that will
outlast the remaining service life of the typical Florida bascule bridges to receive the deck. Required
maintenance should be minimal and the intervals between required maintenance should be consistent
with other Florida bascule bridge maintenance activities (e.g. duration between steel cleaning and
painting, electrical and mechanical system repairs, etc. which typically is every 10 to 15 years.) The
lightweight solid deck should be capable of both localized repair (patching) on short notice using typical
Department maintenance crews, and replacement of individual deck panels with advanced notice.
Procurement duration should be similar to that required for steel open grid panels. Deck systems with
closed voids should have means to access the interior spaces for periodic inspections (e.g. access holes
for cameras.)
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1.3 LIGHTWEIGHT SOLID DECK SYSTEM EVALUATION
1.3.1 Evaluated Deck Systems
In the past 15 years, new materials and technologies have developed that introduce new lightweight
solid decks with weights similar to that of steel open grid deck and potential of solving the issues with
steel open grid deck. This study investigates and evaluates these new deck products in detail to
determine whether there is a viable lightweight solid deck to replace steel open grid decks on typical
Florida bascule bridges. Alternative deck products that are investigated include:
Sandwich Plate System (SPS) Deck by Intelligent Engineering
Aluminum Orthotropic Deck by Sapa Group
Fiber Reinforced Polymer (FRP) Composite Deck by ZellComp, et al.
Ultra‐high Performance Concrete (UHPC) Waffle Slab Deck by FIU/UCF.
1.3.2 Evaluation Process
The alternative lightweight solid deck systems are investigated and evaluated for the deck selection
criteria described above. The investigation included thorough review of available literature, research
and testing and review of in‐service performance of the deck systems in similar applications. Conceptual
level engineering development was performed for each of the deck systems to estimate the deck weight
and corresponding span balance requirements, and required structural modifications.
A Value Engineering (VE) approach was used to provide a reasonable, quantifiable evaluation and
comparison of the different alternatives. The existing steel open grid deck was used as the baseline for
the evaluation and comparison. The alternative lightweight solid deck systems were scored and
compared to steel open grid deck to determine whether the alternative deck system would add value,
and compared with each other to determine which deck offered the most value. In the VE approach,
each of the evaluation criteria is assigned an importance factor, in the form of a percentage of the
overall importance that the criteria are considered in the evaluation. Each of the alternative deck
systems is assigned a value of 1 to 9 for each of the criteria that represent an assessment of the
capability of the deck to addresses the criteria in comparison to steel open grid deck. Steel open grid
deck is assigned a baseline value of 5 for each of the criteria. Values for the alternative deck systems
higher than 5 indicate that the alternative is superior to steel open grid deck for that criteria, while
values lower than 5 indicate that the alternative is inferior to steel open grid deck, and values equal to 5
indicate that the alternative is generally equivalent to steel open grid deck. The values are multiplied by
the importance factor (percentage) and summed to yield a total ranking.
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1.3.3 Evaluation Findings
Steel Open Grid Deck has a total baseline ranking value of 500. Total ranking values for the alternative
deck systems above 500 are generally considered superior to Steel Open Grid Deck and are considered
to add overall value as an alternative deck on typical existing Florida bascule bridges. Total ranking
values below 500 are considered inferior to Steel Open Grid Deck and are generally not considered to
provide overall value. Based on this evaluation, the Aluminum Orthotropic Deck system is the only deck
system to have a value that ranks well above Steel Open Grid Deck (557 vs. 500) and thus is considered
to add value when replacing Steel Open Grid Deck. Ultra High Performance Concrete (UHPC) Waffle
Slab Deck, SPS Deck and FRP Composite Deck systems have values that are slightly above or slightly
below Steel Open Grid Deck (502, 492 and 496 respectively vs. 500). As such, these deck systems are
generally considered to provide similar value to Steel Open Grid Deck. On the basis of this comparison,
the Aluminum Orthotropic Deck is considered superior to the other deck systems that were evaluated,
and offers the most value as an alternative deck system on typical existing Florida bascule bridges, with
the least overall risks and challenges.
Aluminum Orthotropic Deck System: A friction‐stir welded 5‐inch deep Aluminum Orthotropic Deck,
similar to the 8‐inch deep Sapa R‐Section Deck, but fabricated specifically to replace 5‐inch deep Steel
Open Grid Deck, offers a number of advantages and is recommended over the other evaluated
alternative deck systems to replace Steel Open Grid Deck on typical Florida bascule bridges. This
lightweight solid deck system is recommended because of the following reasons:
The solution will address most if not all of the functionality and safety concerns of the Steel
Open Grid Deck.
It provides a nearly weight neutral solution that can be implemented on most typical existing
Florida bascule bridge with minimal changes in overall weight and minimal modifications to the
structure.
The aluminum orthotropic deck is anticipated to be durable and provide a long service life with
excellent resistance to corrosion and other environmental factors, and to protect the bascule
leaf structural steel. The deck is conservatively designed for infinite fatigue resistance and the
use of new friction‐stir welding technology is anticipated to greatly improve the fatigue
resistance.
Although the deck system will have a significantly higher initial construction cost (approximately
twice that required to replace the deck with Steel Open Grid Deck), the longer anticipated
service life, lower maintenance costs, and reduced user impacts (i.e. reduced user delay costs
and accident cost) will offset these higher initial costs.
The deck will span transversely across stringers similar to Steel Open Grid Deck and can be
fabricated in panels of similar width to typical Steel Open Grid Deck panels to facilitate
replacement with short duration closures of the bridge or phased construction while traffic is
maintained. Temporary short‐term repair of the deck top surface is relatively simple and can be
performed quickly by Department maintenance crews with the addition of a field welded
aluminum plates.
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The proposed deck is generally of a robust design that conservatively meets all Strength, Service
(deflection) and Fatigue Limit States in the AASHTO LRFD Bridge Design Specifications. Updated
design specifications for the aluminum orthotropic deck, which utilize simple, conservative
closed‐form equations, have been ratified by AASHTO and incorporated into the latest revision
of the AASHTO LRFD Bridge Design Specifications.
A significant amount of research, development, testing, analysis and evaluation of the very
similar 8‐inch deep SAPA R‐Section Aluminum Orthotropic Deck was previously performed that
supports the design. The proposed 5‐inch deep Aluminum Orthotropic Deck is a direct
derivative of the 8‐inch deep SAPA R‐Section and is conservative by way of use of similar
material thicknesses (top, bottom and web) but with shorter distances between panel points.
There are several recent installations of similar aluminum orthotropic deck products in the
United States and Europe that provide useful information.
Aluminum is a relatively well known material with consistent and predictable material
properties and quality control. Recent advancements in friction‐stir welding have eliminated
the previous concerns with gas metal arc (MIG) welding.
The connection of the deck to the bascule leaf steel framing and splices between fabricated
panels has been researched and there are simple, relatively cost‐effective bolted details that
have been identified.
Concerns with galvanic corrosion due to dissimilar metals, and concerns with thermal
movements due to the difference in coefficients of thermal expansion between aluminum and
steel have been researched and simple, relatively cost‐effective solutions to address these
issues have been identified.
Although the aluminum orthotropic deck system requires a thin epoxy polymer wearing surface,
the significant stiffness of the deck is anticipated to improve the durability and service life of the
wearing surface.
Although the proposed extrusion for the 5‐inch deep Aluminum Orthotropic Deck system was not
available at the onset of this research, SAPA Group, the world’s largest supplier of aluminum extrusions
with a significant number of manufacturing plants in North America, has shown a strong interest in
developing this extrusion, and is in the process of developing the tooling for this extrusion. Because the
proposed section is a direct derivative of the 8‐inch deep SAPA R‐Section, currently in production and
being installed on bridges in the United States, implementation of the similar 5‐inch deep extrusion is
straightforward. The deck will use the latest advancements in friction‐stir welding, similar to that used
to fabricate the SAPA R‐Section. The Department may want to consider limited additional independent
testing of the proposed deck, and corresponding friction‐stir welding, bolted connections, and wearing
surface to supplement the research and development that has already been performed.
UHPC Waffle Slab Deck System: The UHPC Waffle Slab Deck system offers a number of positive aspects
that make it a candidate to replace Steel Open Grid Deck on typical Florida Bascule Bridges including:
The solution will address most if not all of the functionality and safety concerns of the Steel
Open Grid Deck.
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It can be implemented on most typical existing Florida bascule bridges with minimal
modifications to the structure and with a reasonable construction cost.
The high strength, low permeable concrete material is generally anticipated to be durable with
excellent resistance to corrosion and other environmental factors, and that will protect the
bascule leaf structural steel.
The deck will span transversely across stringers similar to Steel Open Grid Deck and can be
fabricated in precast panels of similar width to typical Steel Open Grid Deck panels to facilitate
replacement with phased construction while traffic is maintained.
The concrete deck surface will provide a smooth riding surface with good skid resistance that
eliminates the need for an applied thin epoxy wearing surface.
However, despite the above positive aspects, further research and development of this deck system is
needed before it can be recommended for widespread implementation on typical Florida bascule
bridges.
The current configuration is significantly heavier than existing Steel Open Grid Deck (29 psf vs.
21 psf) and will add significant weight to the trunnion assemblies and bascule leaf structure.
Although there may be opportunities for additional refinements to further reduce the weight,
these refinements are currently theoretical and have not been validated with laboratory testing,
are anticipated to result in corresponding reductions in strength and durability, and introduce
tighter construction tolerances that may make construction difficult or impractical.
UHPC is still considered somewhat experimental with no experience in a similar application on a
bascule bridge.
o There are no design provisions or simple closed‐form equations endorsed by AASHTO
and included in the AASHTO LRFD Bridge Design Specifications needed to ensure a
consistent design methodology by the bridge design community and to simplify the
bridge design process.
o Although research continues to improve knowledge and understanding of UHPC as a
bridge construction material, with corresponding consistency of material properties and
quality control, most bridge contractors and construction inspection personnel working
on bridge repair and rehabilitation projects in Florida are unfamiliar with the use of the
material.
o The UHPC Waffle Slab Deck system has only been placed into service on one fixed bridge
with multiple parallel prestressed concrete girders and has not been installed on a
bascule bridge with a main girder, floorbeam and stringer framing system. It is not clear
whether the limited laboratory testing performed adequately addresses the differences
found in the structural framing configuration found in typical double‐leaf bascule
bridges.
o The long‐term durability of the UHPC Waffle Slab Deck is not generally well known.
Although UHPC provides increased impermeability, concrete cover to the reinforcing
steel, required to achieve a lightweight solution, is limited. Construction tolerances are
anticipated to further reduce the cover. Construction joints between the precast panels
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and cast‐in‐place closure pours introduce opportunities for leakage (i.e. access of water
containing chlorides to the embedded reinforcing steel and structural steel below.)
Continuous deck systems on double‐leaf bascule bridges are subject to tension stresses
(due to cantilever support conditions of the main girders and localized negative bending
of the floor system over the intermediate floorbeams) that act to open the construction
joints.
o There is limited experience with the field repair or replacement of UHPC Waffle Slab
Deck. As such, it is unclear whether effective short‐term localized repairs can be
implemented with this deck system. Although the modular construction of the precast
UHPC Waffle Slab Deck panels makes replacement of individual sections of the deck
practical, the grouted haunches with welded headed stud shear connectors complicates
the replacement and will slow the replacement process. It is not clear whether a
damaged panel can be replaced in a short duration nighttime closure.
FRP Composite Deck Systems: There are a number of available FRP Composite Deck systems, each of a
different design including overall deck thickness; structural configuration; manufacturing process; type,
size, orientation, and number of layers of fiber reinforcing; type of resin; and associated physical
properties including weight, strength, stiffness and span capability. Different FRP Composite Deck
systems utilize different installation and construction practices including different deck attachment
details. Despite the differences in these products, there a many similarities in the overall performance
of these deck systems that permits the FRP Composite Deck to be evaluated as a single technology.
FRP Composite Deck systems offer a number of positive aspects that make them a candidate to replace
Steel Open Grid Deck on typical Florida Bascule Bridges including:
The FRP Composite Deck systems will address most if not all of the functionality and safety
concerns of the Steel Open Grid Deck.
They can provide a nearly weight neutral solution that can be implemented on most typical
existing Florida bascule bridge with minimal changes in overall weight and minimal
modifications to the structure with a reasonable construction cost.
The FRP composite material is a corrosion resistant.
FRP Composite Decks generally offer good overall capacity at the Strength Limit State.
The deck will span transversely across stringers similar to Steel Open Grid Deck and can be
fabricated in prefabricated panels of similar width to typical Steel Open Grid Deck panels to
facilitate replacement with short duration closures of the bridge or phased construction while
traffic is maintained.
The modular nature of some FRP Composite Deck systems permits the replacement of individual
panels should that become necessary.
Although each available FRP Composite Deck system is considered proprietary, because each of
the FRP Deck systems generally yields a similar solution, there are opportunities for competitive
bidding.
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However, despite the above positive aspects, further research and development of the available FRP
Composite Deck systems is needed before they can be recommended for widespread implementation
on typical Florida bascule bridges.
FRP Composite Deck installations throughout the United States including those on several
bascule bridges have generally exhibited durability issues and limited service life. Although FRP
Composite Deck systems continue to improve as the technology evolves and more is learned
about the design requirements, there are significant issues with current available designs that
still need to be addressed. Some deck systems have performed better than others in specific
areas of evaluation. For example, conservative designs with stronger and stiffer section
properties and shorter deck spans have performed better than those with less conservative
designs. Joints between deck panels and wearing surfaces continue to be primary sources of
premature failure in FRP Composite Deck systems.
Much of the research and development of FRP Composite Decks has not considered critical
stresses and deformations that are unique to bascule bridges including those associated with 1)
main girder cantilevered support conditions that introduces longitudinal membrane stresses in
the continuous deck in conjunction with main girder flexure, and 2) floor system configuration
with stringers and floorbeams that introduces tension in the continuous deck corresponding to
stringer end rotations and negative bending of the deck over the intermediate floorbeams.
Currently available FRP Composite Deck systems are proprietary and do not appear to have
strong financial and technical support from a large corporation with significant resources.
Although there is a significant amount of research that has been performed on FRP composites
for use as bridge decks, the research for each individual deck product is generally limited.
Currently there are no design provisions for FRP Composite Decks endorsed by AASHTO and
included in the AASHTO LRFD Bridge Design Specifications. Although there are some
recommended guidelines for designing FRP Composite Deck, offered by some manufacturers,
some state transportation agencies, and FHWA, there appears to be little consistency, a wide
range of assumptions used, and varying design practices used throughout the United States.
FRP Composite Decks are somewhat flexible and are designed for larger deflection limits than
currently used in Steel Open Grid Deck design. Many FRP Composite Deck suppliers recommend
deflection limits of L/500 when AASHTO requires a deflection limit of L/800 for steel grid and
other lightweight metal decks. (NOTE: For comparison, the deflection of the 5‐inch deep
Aluminum Orthotropic Deck for the same deck span meets a deflection limit of L/3000.) There
are questions as to whether a deflection limit of L/500 is appropriate for bascule leaf decks.
Although this deflection is not considered an issue for motorist comfort and safety, the
significantly greater deflections are a concern for the performance of the thin epoxy polymer
wearing surface.
Testing has shown that the physical properties (e.g. strength and stiffness) of the FRP composite
materials degrade with repeated loading. Although this degradation can be accounted for by
conservatively specifying larger section properties, the degradation introduces questions
regarding the long‐term durability of the deck and the performance of the wearing surface over
time as deflections increase with the degradation.
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Durability of FRP Composites is dependent on a number of factors including the manufacturing
processes, and properties of the epoxy resin material and associated coatings that encapsulate
the fiber material. Construction practices (including cutting and drilling of the FRP composite
material) can reduce the durability by exposing the embedded fiber material to environmental
factors. Exposure of the fiber material to chemicals, ultra‐violet light, and even salt water can
result in degradation. There is a wide range of manufacturing processes, materials and
construction practices used in implementing the various available FRP Composite Deck products.
Currently, there are no industry standards endorsed by AASHTO that define the specific
manufacturing, construction, inspection and testing requirements (e.g. quality control)
necessary to assure that an FRP Composite Deck product is durable and will provide the
anticipated long‐term service life.
FRP composite materials are not currently well known to the bridge construction industry. The
technology requires specialized shop inspection and field inspection practices that are
unfamiliar to most bridge construction inspection personnel.
SPS Deck System: The SPS Deck system offers a number of positive aspects that make it a candidate to
replace Steel Open Grid Deck on typical Florida Bascule Bridges including:
The SPS Deck system will address most if not all of the functionality and safety concerns of the
Steel Open Grid Deck.
It can be implemented on most typical existing Florida bascule bridges with minimal
modifications to the structure and with a reasonable construction cost.
SPS Deck generally offers good overall capacity at the Strength Limit State.
Although SPS Deck utilizes technology that is unfamiliar to most bridge contractors performing
work on bridge repair and rehabilitation projects, the field installation generally utilizes
conventional steel erection practices.
However, despite the above positive aspects, further research and development of this deck system is
needed before it can be recommended for widespread implementation on typical Florida bascule
bridges.
The lightest recommended SPS Deck solution, required to meet deflection limits is significantly
heavier than existing steel open grid deck and will add significant weight to the trunnion
assemblies which typically have very limited or no reserve capacity. The sizing of the SPS Deck is
governed by deflections and because the modulus of elasticity of the elastomer core decreases
with increased temperatures, a thicker core is required in Florida where temperatures are
generally higher than northern states. Significant additional modifications to the bascule leaf
are required to offset the increase in weight. This includes replacement of a number of bridge
components with lighter elements that do not otherwise need replacement, which adds
unnecessary cost to a project.
The lightest recommended SPS Deck is somewhat flexible and is designed for deflection limits
equal to L/300 for deck span (i.e. stringer spacing) typically found on Florida bascule bridges.
(NOTE: For comparison, the deflection of the 5‐inch deep Aluminum Orthotropic Deck for the
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same deck span meets a deflection limit of L/3000.) There are questions as to whether a
deflection limit of L/300, recommended by Intelligent Engineering consistent with the deck plate
of steel orthotropic bridge decks, is appropriate for bascule leaf decks when AASHTO requires a
deflection limit of L/800 for steel grid and other lightweight metal decks. Although, this
deflection is not considered an issue for motorist comfort and safety, the significantly greater
deflections are a concern for the performance of the thin epoxy polymer wearing surface.
In order to minimize the weight of the deck system (i.e. reduce the number of heavy perimeter
and splice bars), the SPS Deck panels must be configured such that the longer dimension of the
panel is parallel to the roadway centerline. Because this configuration is opposite to that of the
existing steel open grid deck, the deck cannot be replaced in small sections (e.g. one floorbeam
bay at a time) without adding additional panel splices, which further adds weight to a deck
system that is already significantly heavier than the existing steel open grid deck.
SPS Deck requires a significant amount of field welding to splice the panels. The fully welded
panels make future rapid replacement of sections of the deck a challenge.
Currently there are no design provisions for SPS Deck design endorsed by AASHTO and included
in the AASHTO LRFD Bridge Design Specifications. Although there are some guidelines and
available simplified tools for selecting an SPS Deck, in order to achieve the lightest possible deck,
Intelligent Engineering recommends that a full non‐linear finite element analysis of the deck and
framing system be performed, which makes the design process more cumbersome and adds
cost to the project. The need to use finite element analysis to design and analyze the deck
introduces some concerns and challenges regarding future load rating and overload permitting.
SPS Deck utilizes technology that is unfamiliar to the bridge construction industry (e.g. use of
polymer core). The technology requires specialized shop inspection practices unfamiliar to most
bridge construction inspection personnel.
Although there is a significant amount of research that has been performed on SPS Deck over
the last 15 years with impressive results, the limited use of SPS as a bridge deck material
introduces some risk as to the long‐term performance. There have been reported issues (deck
failures) on more than one bridge in Canada, less than one‐year after the SPS deck was placed
into service. The issues associated with these failures will need to be fully investigated and the
solutions to the cause of the failures developed and tested.
In the following report, each of the lightweight solid deck alternatives is described and discussed in
greater detail with consideration of each of the evaluation criteria. In addition, because all of the
evaluated deck systems, except for the UHPC Deck system, require an independent wearing surface, and
the available wearing surfaces for each of the deck systems are similar, a separate description and
discussion on alternative wearing surfaces is also included.
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2.0 OVERVIEW OF EVALUATED LIGHTWEIGHT SOLID DECK SYSTEMS
In‐depth evaluation was performed on the following four (4) lightweight solid deck systems:
Sandwich Plate System (SPS) Deck by Intelligent Engineering,
Aluminum Orthotropic Deck by Sapa Group,
Fiber Reinforced Polymer (FRP) Composite Deck by ZellComp, et al.,
Ultra‐high Performance Concrete (UHPC) Waffle Slab Deck by FIU/UCF.
Following sections include product description, development background, and potential as a viable
alternative for steel open grid decks on typical Florida bascule bridges using the various criteria listed in
Introduction and Executive Summary.
2.1 SANDWICH PLATE SYSTEM (SPS) DECK
2.1.1 Description
The Sandwich Plate System (SPS) is a proprietary and patented composite laminate plate material
consisting of thin metal faceplates continuously bonded to a polyurethane elastomer core. The
elastomer core transfers forces between the metal faceplates by way of shear, analogous to an I‐beam
when subjected to flexure with the steel plates acting as the flanges and the elastomer core as the web.
The elastomer core also prevents local buckling of the metal faceplates in compression, which permits
development of full yield of the metal faceplates.
SPS panels are very thin (1 to 2 inches thick) compared to traditional bridge decks. The use of these thin
panels is possible through a combination of panel bending and membrane action (i.e. in‐plane tension).
Separation of the thin metal plates with a lightweight elastomer core more efficiently increases strength
and stiffness of the plate, while minimizing the increase in weight of the plate.
The thickness of the steel plates and the elastomer core is typically customized to fit a given application
and for the required strength and stiffness. SPS panels are identified by a designation such as “SPS 6‐25‐
6”. The first and last numbers indicate the steel plate thicknesses in millimeters and middle number
indicates the core thickness in millimeters. An SPS bridge deck is typically constructed from a series of
panel segments, connected together and to the supporting steel framing.
SPS Sample‐Size Specimen
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Elastomer bubbles (i.e. formed voids within the elastomer core) have been used to reduce the weight of
the SPS panels. However, this technology has not been used in bridge decks where the deck plate is
subject to large concentrated wheel loads.
Applications: SPS panels have been used in different highway bridge deck applications including:
Strengthening and stiffening existing steel orthotropic decks,
Replacement of conventional decks on existing multi‐girder bridges,
Decks for new bridges in both orthotropic deck and conventional multi‐girder configurations.
Materials: For bridge applications, metal faceplates are typically fabricated from steel (e.g. ASTM A588,
Grade 50W).
The elastomer formulation is proprietary, but physical properties of the formulation required for design
such as modulus of elasticity, Poisson’s ratio, density, etc. are published and available. The density of the
elastomer is 1150 kg/m3 (71.8 pcf).
Properties of the elastomer change with variations in temperature. The modulus of elasticity of the
elastomer varies significantly with changes in temperature. As the temperature of the elastomer
increases, the modulus of elasticity reduces, and deflections of the SPS deck will increase. The ultimate
strength of the elastomer also varies with temperature. As temperature increases, the ultimate
strength of the elastomer decreases. Poisson’s ratio varies very little with changes in temperature. The
elastomer also has a different modulus of elasticity in tension and compression. The shear modulus of
the elastomer is load rate dependent, with faster loading rates resulting in a higher shear modulus.
Material Properties of Elastomer at Various Temperatures
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2.1.2 Product Development and Corporate Information
SPS was initially developed in the mid 1990’s to provide impact resistant plating for offshore structures
and ice islands working in the Canadian Beaufort Sea. SPS applications have since expanded to ship hulls
and deck plates, stadium terraces, building floor systems, bridge decks, and blast walls. Currently,
approximately 325,000 square feet of SPS have been fabricated and installed in different applications
worldwide.
The technology was developed by Dr. Stephen Kennedy, former Professor of Civil and Environmental
Engineering at Carlton University in Ontario, Canada. Dr. Kennedy is currently the Chief Technical
Officer at Intelligent Engineering (IE) in Ottawa Ontario, Canada. IE was founded in 1996, and currently
has offices in Canada, United Kingdom, Singapore, and Dubai. IE partner0s with Elastrogran GmbH, part
of BASF, which developed the polyurethane elastomer core for the SPS. IE also provides licenses to
various companies to produce the SPS product. More information regarding IE can be found at
www.ie‐sps.com.
2.1.3 Constructability
Fabrication: SPS panels for bridge decks are typically fabricated at a steel fabrication facility specifically
licensed by IE to fabricate the panels. However, field fabrication has also been used to retrofit existing
steel orthotropic decks. Steel faceplates are cut to the required size, the top and bottom faceplates
separated and an airtight space created with steel perimeter bars continuously welded to the steel
faceplates along the edges. Panels are not typically cambered.
Bond between the steel faceplates and elastomer is developed by intentionally roughening the interior
surfaces of the steel faceplates using shot blasting or grit blasting. The bond strength varies depending
on the anchor profile achieved. Steel coatings will generally reduce the bond. The bond strength is
also temperature dependent with lower temperatures yielding greater bond.
A two‐part liquid polyurethane elastomer is then injected into the airtight space. To prevent sagging of
the top faceplate, a series of small, circular cured elastomer spacers, equal to the thickness of the
elastomer core, are spaced throughout the panel. Because the elastomer experiences some expansion
and high temperatures during the exothermic curing process, the SPS panels require restraining frames
on top of the panels to prevent distortions and maintain flatness of the panels.
The elastomer core is extremely sensitive to moisture during the curing process, which can lead to
swelling. As such, the cavity to be filled with elastomer must be dry and the humidity of the air in the
cavity maintained below a specified limit, which is achieved with hot air dryers and verified with
humidity and temperature measurements taken in the cavity.
The SPS panels can be made to various custom sizes, limited in size by the pumping speed and setting
time of the elastomer, although multiple pours of elastomer are possible. The volume of the elastomer
is limited to 1,200 liters (42.4 cubic feet), which limits a 1‐1/8‐inch (30 mm) core (recommended for
typical existing bascule bridges in Florida) to approximately 450 square feet.
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Because the panels are fabricated using structural steel, the panels can be fabricated to the same
dimensional tolerances as other structural steel members. Mill tolerances in ASTM A6 and the
fabrication tolerances in the AWS D1.5 Bridge Welding Code are applicable to panel fabrication.
SPS Deck System Fabrication
Specialized Inspection: SPS deck and thin epoxy polymer wearing surfaces are less common to the
bridge industry and thus inspection of this construction will, at least initially, be considered specialty in
nature.
Fabrication of the SPS deck will require typical steel fabrication and weld inspection. The fabricator will
be required to perform quality control and submit weld procedures specifications and certifications and
a quality control plan that addresses the required quality control functions to be performed. Because of
the special requirements of the elastomer core and SPS panels, it may be necessary to employ personnel
with specialized experience to perform quality assurance for this work. Field welding of the panel
splices will require on‐site involvement by welding inspectors. The contractor will be required to submit
weld procedure specifications and certifications for the field welding. Quality control procedures for the
wearing surface will also need to be developed.
Field Installation: The SPS panels can be fabricated of a size that can be shipped to the site by truck
without special permitting. Widths of the panels are anticipated to be no more than 8 feet and lengths
no longer than 40 feet, which is consistent with maximum dimensions of steel open grid deck panels.
SPS panels can be stored by staking the panels on top of each other to minimize staging areas similar to
steel open grid panels. SPS panels are relatively flexible and require use of lifting beams to handle and
place the panels similar to steel open grid panels.
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Bolting of the panels can be performed using standard turn‐of‐nut method or direct tension indicator
washers similar to standard steel erection work. Special adapters may be required for the Skidmore
device to calibrate the countersunk bolts to snug‐tight condition. Tapered pins can be used to align
predrilled holes in the steel members similar to typical steel erection.
The top flange of the new stringers can be match drilled with the SPS panels in the shop to improve
alignment of the holes and reduce time consuming field drilling. The stringer end connections can
remain blank and drilled from solid to match existing holes in the webs of the floorbeams or pre‐drilled
for use as a template to drill new holes in the floorbeam webs to maximize field adjustment.
The open joint between the ends of the panels and curbs or traffic railings provide clearance to
accommodate tolerances in panel width. A small grouted closure pour can be provided at the
counterweight to accommodate tolerances in the panel lengths. Tolerances in panel sweep and
squareness can be accommodated in the root opening of the field welded joint. The flexibility of the SPS
panels should be sufficient to accommodate any unanticipated small camber in the panels or tolerances
in the elevation of the supporting members.
Traffic Control: Because the SPS panels are oriented having the long dimension parallel to the roadway
centerline and steel open grid panels are oriented with the long direction perpendicular to the roadway
centerline, and the stringers require replacement with the deck, there will be challenges in maintaining
traffic on the bascule span while the deck is replaced. It may be possible to replace the deck in larger
sections equal to the length of the SPS panels (one‐half to one‐third the length of the bascule leaf) and
the full‐width or half‐width of the bridge, while the bridge is temporarily closed to traffic. However, it
will not be practical to perform the replacement a single panel at a time or even a single floorbeam bay
at a time. The use of smaller SPS panels that match the steel open grid panels will require many more
splices that will significantly increase the weight of an already heavier deck system. Because panels
should generally be of a dimension that can be shipped by truck, this limits the number of configurations
that can be used to accommodate phased replacement of the deck.
2.1.4 Functionality and Safety
Load Capacity: An SPS deck designed to governing deflection limits will have corresponding load
carrying capacity in excess of that required to support AASHTO LRFD HL‐93 Live Loads. The small
increase in deck weight resulting from the heavier SPS deck is not anticipated to significantly reduce the
capacity of the bascule span. There are opportunities to increase the load carrying capacity of the
stringers and main girders by taking advantage of the composite action between the SPS deck these
members.
Rideability: SPS deck and the corresponding applied wearing surface will provide a smooth, continuous
riding surface with a surface roughness comparable to asphalt or concrete pavement. Because the SPS
deck is more flexible than the existing steel open grid deck, localized deflections are anticipated to
increase. However, because the SPS deck will be made composite with the stringers and main girders,
the overall deflections and vibrations of the bascule leaf are anticipated to decrease, which will improve
the quality of the ride.
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Skid Resistance: Skid resistance from the applied wearing surface will be similar to that of asphalt
pavement. See Section 3 Wearing Surface Evaluation.
Noise: The vibration dampening characteristics of the elastomer core will significantly reduce noise
generated by tires in contact with the deck.
Bicycle Safety: SPS deck provides a solid riding surface for the roadway and shoulders with small
longitudinal open joints (less than ½” wide) located immediately adjacent to the curbs or barriers, which
will greatly improve bicycle safety. Transverse deck joints between the two bascule leaves and between
the bascule span and bascule pier will range from ¾” to 1½” in width, but should not be a concern for
bicyclists.
2.1.5 Design and Analysis
Design Considerations: The design of SPS bridge decks is not specifically addressed in the AASHTO LRFD
Bridge Design Specifications. Furthermore, because of the unique configuration and materials of SPS
deck, it is not clear how it should be classified when implementing specific governing AASHTO design
provisions and guidelines. SPS deck is comparable to steel orthotropic deck in that it utilizes continuous
metal deck plate. However, SPS deck differs significantly from steel orthotropic deck in that the main
structural resistance of an SPS deck is derived from the face plates and core, whereas the steel
orthotropic deck derives its resistance from the deck plate and discretely spaced stiffening elements
acting together as a unit. It is not clear whether the longitudinal support beams (e.g. bascule leaf
stringers) can be considered as the discretely spaced stiffening elements and the SPS deck as the deck
plate of a steel orthotropic deck due to the significantly wider spacing of these elements in an SPS deck
solution.
Virginia Polytechnic and State University has performed research and has developed a simplified
methodology to design the SPS deck. It should be recognized that the proposed design methodology,
which considers a number of AASHTO provisions including loading and limit states, has not been
formally reviewed and endorsed by AASHTO. Furthermore, the design methodology has not been
calibrated to an established reliability index.
As the SPS deck system is a thin, flexible system, the design of SPS decks is controlled by deflections. As
the design of SPS decks is not specifically addressed in the AASHTO LRFD Bridge Design Specifications, it
is unclear which deflection limits are applicable to SPS deck. There are two different provisions of
AASHTO Article 2.5.2.6.2 (Criteria for Deflection) that could apply.
If SPS deck system is classified as a steel orthotropic deck with the SPS member considered the
deck plate and the stringers considered as the stiffening ribs, then the provisions for orthotropic
deck would be applied. These provisions include L/300 deflection limits of the deck plate,
L/1000 for the stiffening ribs, and 0.1 inch maximum relative deflection between adjacent ribs
from a combination live load and dynamic load allowance. These provisions also make the
deflection limits mandatory. (NOTE: IE recommends and uses this less conservative assumption
in their design guidelines).
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If SPS deck system is classified as “metal grid decks and other lightweight metal and concrete
bridge decks”, similar to steel open grid decks, then the serviceability provisions of AASHTO
Article 9.5.2 apply. These provisions include L/800 deflection limits from a combination of live
load and dynamic load allowance. It also makes the deflection limits mandatory. (NOTE:
Researchers at Virginia Polytechnic Institute and State University use this conservative
assumption).
There are several factors that must be considered in making a decision regarding the design of the deck
for deflections:
The selection of a deflection limit (i.e. L/800 vs. L/300) yields significant differences in the final
SPS deck design and makes a difference whether the solution is viable or not viable (i.e. the
weight of an SPS deck based on a deflection limit of L/800 will be much heavier and difficult to
accommodate with existing counterweights and trunnion assemblies, while the weight of an SPS
deck based on a deflection limit of L/300 will be lighter and can be accommodated).
The effect of deflections on driver comfort is not likely to be a concern for the anticipated deck
span lengths. Live load deck deflections are anticipated to be small (i.e. less than ¼”) and are
anticipated to remain constant over the length of the bascule span (i.e. deflections will not vary
over the length of the bascule span and cause vertical accelerations that affect driver comfort).
For the typical bascule span framing configuration, maximum deflections will occur directly
under the wheel and deck stiffness will generally remain uniform over the length of the bascule
span where the deck is supported only by the stringers and not directly supported at the
floorbeams. Research indicates that vertical acceleration limits is a more appropriate means of
addressing driver comfort than arbitrary deflection limits.
Various studies regarding dynamic amplification of live loads indicates that dynamic
amplification values increase with decreasing bridge stiffness. As such, dynamic load allowances
specified by AASHTO may underestimate actual values on flexible decks. A conservative
estimate of the dynamic load allowance is recommended for the SPS deck design if more flexible
L/300 deflection limits are used.
Excessive deflections may result in durability concerns for the wearing surface. Wearing surface
durability is a well‐documented concern on bridges with orthotropic decks with flexible deck
plates. There are no available studies that have tested the durability of thin epoxy polymer
wearing surfaces on flexible SPS decks.
In order to reduce the weight of the SPS deck, lightweight thin wearing surfaces are required.
Thin wearing surfaces do not have the ability to distribute wheel contact pressures to a larger
surface area like thicker asphalt wearing surfaces used on most of the SPS deck installations. As
such, wheel patch loads are likely more concentrated. However, laboratory testing of SPS decks
has typically taken a conservative approach that neglects the load distribution benefit of the
asphalt wearing surfaces.
The modulus of elasticity of the elastomer core reduces with increased temperatures and
temperatures in Florida are generally higher than those in northern climates where most of the
SPS decks have been installed. As such, it is recommended that a conservative approach be
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used in the design of the deck for deflections using modulus of elasticity values corresponding to
maximum anticipated in‐service temperatures in Florida.
Design Approach: Because of the inherent complexities of the materials and load‐deflection
characteristics of SPS, deck design has relied heavily on finite element models. IE has traditionally
performed the design using a second order non‐linear inelastic finite element analysis. Due to the
complexity of this analysis, it is not practical for each design consultant providing bascule bridge
rehabilitation design engineering services to develop the skills to properly perform this analysis.
Furthermore, the budgets typical of bascule bridge rehabilitation projects are generally inadequate to
cover the expenses for such analysis. A simplified analysis technique should be used by the design‐
consultant to conservatively estimate the size of the SPS panels (steel faceplate and elastomer core
thickness) for purposes of developing the contract plans including associated modifications (e.g. steel
framing, counterweight, machinery, etc.) for estimating and bidding purposes. IE can perform the in‐
depth finite element analysis and refine the deck during the procurement of the deck and during the
panel procurement and the cost of this analysis included in the cost of the deck.
Virginia Polytechnic Institute and State University developed simple, conservative closed‐form equations
that can be used for the preliminary sizing of SPS deck on the basis of AASHTO LRFD Bridge Design
Specifications. In developing the proposed design method all applicable AASHTO LRFD design limit
states were considered (Strength I, Service I, Service II, and Fatigue). Research identified that the
controlling limit state for design was Service I with the deflection limit of L/800 imposed. The closed‐
form equations were validated by comparison to experimental data from both field and laboratory
testing and then extended to consider the design limit states within AASHTO LRFD including
serviceability, strength, and fatigue. The closed‐form equations were conservatively developed for
simple (pinned) boundary conditions and do not consider continuity provided by deck span over
multiple supports, or stiffening effects from transverse supports that yield two‐way span of decks.
Actual boundary conditions are between upper and lower bounds (pinned or fixed conditions).
The closed‐form equations were used to plot solutions in a graphical form for different deck flexural
rigidities and span lengths. The closed‐form equations can also be programmed into a software
program (e.g. Excel Spreadsheet or MathCAD). A solution can be achieved as follows:
1) Establish a deck span “S”.
2) Determine the required flexural rigidity of the deck to meet the design criteria listed above using
the following equation:
3738 ∗ 2551 ∗ ∗
3) Check the provided flexural rigidity based upon the face plate thickness and the elastomer core
thickness chosen. Elastomer properties should be based upon IE published data, adjusted for
the maximum in‐service design temperatures of the deck. The subscript “p” is for the steel face
plate. The subscript “c” is for the elastomer core.
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The conservative deflection limits and boundary conditions generally yield SPS deck solutions that are
overly conservative. Although this approach is generally prudent, it yields deck designs that are heavier
and that will not be viable to replace a lighter steel open grid deck on a bascule bridge. The use of more
liberal deflection limits (e.g. L/300) can be addressed, if desired, by adjusting deflection values.
However, as noted above, the decision to use more liberal deflection limits may have adverse
consequences in the performance of the wearing surface and possibly other elements of the deck. A
more accurate assessment of the effects of continuity can be addressed by interpolating between the
graphs for the upper and lower boundary conditions (i.e. pinned and fixed).
IE recommends that the deck plate thickness not be less than 3/16‐inch (5 mm) to ensure that fatigue of
the base material does not occur during the life of the structure.
2.1.6 Durability and Service Life
Service Life: It is anticipated that a properly designed SPS deck system will provide a minimum service
life that exceeds the life of a typical existing bridge (i.e. 30 to 40 years). However, because SPS is
relatively new (i.e. less than 10 years of experience in bridge deck applications and slightly more than 15
years in other civil and maritime applications) there are no installations close to this age that confirm
that this service life can be achieved.
Fatigue Resistance: The bond between the relatively stiff elastomer core and the thin metal faceplates
eliminates the need for welded stiffener plates and the stress concentrations and fatigue sensitive
details associated with these stiffeners. The continuous fillet welds between the faceplates and
perimeter bars and the continuous fillet or groove welds used to splice panels together introduce
fatigue sensitive details that must be considered in the design of the deck. However, these details
generally have relatively high fatigue resistance that does not control the design of the deck panels (i.e.
deflection limits typically control the design of the deck panels).
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The fatigue category for the welded connection used in the splice detail is not specifically identified in
AASHTO LRFD Bridge Design Specifications. However, there are details that are similar and that can be
used for reference. Until more extensive testing of this joint is performed, a conservative value for the
fatigue stress limit is recommended.
The bond between the elastomer and the steel has been found to be essentially fatigue insensitive
unless the bond has been locally damaged from such effects as high, localized heat from welding or
cutting, or freezing of water that has entered the core.
Corrosion Resistance: Because the SPS panels are fabricated from steel plates, the panels are
susceptible to corrosion. As such, the panel exterior surfaces must be protected with steel coatings
similar to other steel members. Steel coatings can consist of the same coatings used on the other bridge
structural members. Metallizing the exterior steel surfaces can also be used without concerns of
adverse effects to the elastomer core. The simple, flat surfaces of the SPS panel underside simplify the
cleaning and painting. The use of corrosion resistant mechanically galvanized bolts, similar to those
currently used for steel structures in coastal environments in Florida, also simplify the coating
operations. Some caulking of joints and faying surfaces may be required in conjunction with this work.
The thin epoxy polymer, wearing surface protects the top faceplate from corrosion. However, it is
important to prevent water from leaking through defects in the wearing surface and reaching the steel
plate, as this can lead to corrosion. Corrosion of the top steel faceplate can result in delamination and
failure of the wearing surface. As such, it is recommended that a flexible water proofing membrane be
applied between the top surface SPS panels and the wearing surface.
Impact Resistance: SPS deck is anticipated to have good impact resistance in the event that a vehicle
overturns and impacts the deck surface. SPS was specifically developed to provide impact resistant
plate for offshore platforms and other maritime facilities and has been thoroughly tested to
demonstrate this capability. This testing demonstrates that SPS has excellent energy absorbing
properties to resist collision, ballistic projectiles and explosions.
Fire Resistance: SPS panels have been thoroughly tested for fire resistance in maritime (shipping)
applications. Testing demonstrates that SPS has an equivalent fire rating of A60 according to the
International Convention for Safety of Life at Sea (SOLAS) regulations. SPS panels are non‐combustible
under fire conditions. In the event of a fire, the elastomer core acts as an insulator, and protects
elements on the opposite side of the SPS panel, away from the fire. However, heat from the fire will
likely damage the SPS faceplates and elastomer core. In the case of a hot fire, the elastomer core
exposed to the heat from the fire may transform into a gas, and vent out of the panels if there is a
breach in the faceplates.
Similar to other steel members, steel loses strength and stiffness when exposed to high temperatures
(i.e. greater than 1100 degrees F). Similar to other steel members, SPS panels are likely to survive short
duration fires and/or fires with lower temperatures. Because the loss of strength is time‐dependent,
panels may provide limited structural support for loads on the deck during a fire (e.g. the vehicle on fire,
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emergency response vehicles and personnel). If the deck panels lose strength during these events, the
steel framing below may steel provide some support to contain vehicles.
Only a substantial heat source, such as that from a roadway accident with ignited localized fuel spill, is
expected to threaten the integrity of SPS deck.
Thermal Expansion: Because SPS panels are fabricated from steel, similar to the bascule leaf steel
framing, differential thermal expansion between the panels and the steel framing will not be a concern.
The difference in coefficients of thermal expansion between the elastomer (126.9‐155.6 x 10‐6 to m/m°C
for temperature range of 0 to 40 °C) and steel faceplates (11.7 x 10‐6 m/m °C) is a potential concern and
risk at normal in‐service temperature ranges in Florida. The thermal contraction of the elastomer can
result in loss in bond and the elastomer separating from the faceplates near the ends of long panels.
Anchor bars consisting of a jagged plate attached to the faceplates within the cavity near the ends of the
plate are recommended to address this concern.
Chemical Resistance: The elastomer core has been tested to determine the resistance to a number of
chemicals including saltwater for maritime (shipping) applications. Because the elastomer is injected
into an airtight cavity when the panels are fabricated, the elastomer is fully isolated from exposure to
chemicals, unless there is a breach in the faceplates. Breaches at the bolted connections have been
identified in some circumstances that has allowed water to enter the core.
The steel faceplates provide similar resistance to chemicals as other steel elements on the bridge. Paint
coatings and wearing surface provide limited protection of the steel from chemicals and long term
protection from corrosion.
Ultraviolet (UV) Light Resistance: Because the elastomer is injected into an airtight cavity when the
panels are fabricated, the elastomer is fully isolated from UV light.
2.1.7 Maintenance
Repair: Damaged panels may be repaired by cutting and removing the damaged section, or by fully
removing and replacing the entire panel. Local repair involves removing the damaged steel and
elastomer, making sure that the elastomer is removed a sufficient distance from the steel cut line to
prevent the weld heat from damaging the remaining elastomer. A new steel plate is then butt‐welded
to repair the hole, and new elastomer pumped into the cavity where elastomer had been removed.
Because the repair involves injection of new elastomer material into the core, which involves specialty
work, repairs by Department maintenance personnel are not practical. Required emergency repairs
may result in closure of the bridge for extended periods until the specialty work forces can be mobilized.
Periodic Maintenance: The steel SPS panels will periodically require cleaning and painting at the same
time and with the same paint system as the other bascule span steel members. More expensive, but
longer lasting metallized coating systems can be used with the SPS panels to extend the duration
between coatings.
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The wearing surface on the SPS deck will require periodic (every 10 to 15 years for thin epoxy polymer
wearing surface) replacement (see Section 3 Wearing Surface Evaluation).
2.1.8 Research
Design of SPS continues to evolve and significant research has been performed on SPS since its
inception. From 2005 through 2012, a significant amount of research has been conducted at Virginia
Polytechnic Institute and State University specifically related to the use of SPS as a bridge deck to
AASHTO LRFD Bridge Design Specifications. Additional similar research has been performed at the
University of Alberta in Canada to the Ontario Highway Bridge Design Code. Research has been used to
verify SPS deck behavior including:
Composite behavior between SPS deck and supporting steel girders including shear lag effects,
effective width of composite deck, and efficiency of slip critical connections to achieve
composite action,
Fatigue behavior of several proposed welded and bolted connections and splice details including
identification of fatigue category, S‐N curves, and endurance limits,
Ultimate strength of SPS deck panels under concentrated loads simulating wheel patch loads,
Steel‐elastomer bond behavior and required surface preparation to achieve the required bond
and shear transfer,
Fatigue of steel‐elastomer bond damaged by high heat from welding,
Confirmation of load deflection models and establishment of simplified design methodology.
Research has included a combination of finite element analysis, classical plate analysis, laboratory and
field testing.
A significant amount of additional material and load testing, not directly specific to use of SPS as a
bridge deck, but applicable due to similarities in other civil engineering and maritime uses, provides
confidence that SPS is a durable and safe product. This testing included significant testing and
evaluation of the elastomer material at different temperatures including that required to establish:
Mechanical properties including density, tensile and compressive behavior, shear modulus,
Poisson’s ratio,
Thermal properties including thermal expansion coefficient, specific heat, thermal conductivity,
R‐value and thermal diffusivity,
Saltwater resistance including absorption and effect on material properties,
Chemical resistance for numerous chemicals,
Tensile impact toughness,
Hardness.
2.1.9 Recent Bridge Installations
Several highway bridges have been constructed to date using SPS deck including those described below
to provide additional confidence in the performance of the deck system. Although none of the bridges
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constructed to date are movable bridges, IE has proposed SPS deck for several bascule bridges and has
performed preliminary design including detailed finite element analysis of these bridges.
Shenley Bridge: The Shenley Bridge, built in 2003 in Saint‐Martin, Quebec, Canada was the first bridge
constructed using an SPS deck. The bridge is described as follows:
Two‐lane bridge, 73.8 ft span, with
three steel plate girders and SPS 6.4‐
38‐6.4 deck system (ASTM A588
Grade 50 steel).
Designed to Canadian Highway
Bridge Design Code with CL‐625
design truck. IE designed the bridge
using the finite element analysis
(ANSYS Software was used). Deck
was designed as composite with
steel girders, using L/400 deck
deflection limit.
Construction performed in 14 days.
Individual panels utilize slip‐critical bolted connections to supporting structure and are spliced
by field welding.
A water‐proofing membrane coating (Stirling Eliminator) was applied to the top face of the SPS
below a 50 mm asphalt wearing surface.
Guardrails were bolted to perimeter angles welded to the SPS deck.
Composite action was confirmed by field‐testing of the bridge.
Lennoxville Bridge: The Lennoxville Bridge, rehabilitated in 2005 in Lennoxville, Quebec, Canada
included installation of an SPS deck on the existing
stringers.
The bridge is an historic through‐truss
bridge.
Replacement of the existing concrete deck
with a 60% lighter weight SPS 6‐38‐6 deck
and asphalt wearing surface was specified to
address structural deficiencies and increase
the capacity of the trusses. Pedestrian
walkways also consist of SPS panels
supported on brackets cantilevered
outboard the trusses.
The deck was made composite with the
existing steel girders.
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Deck sections are bolted together and to the supporting steel beams and the deck panels are
additionally field welded.
The entire SPS deck (16 panels) was installed in a week.
Cedar Creek Bridge: The Cedar Creek Bridge, built in 2008 in Wise County, Texas is the first bridge with
an SPS deck constructed in the United States
The bridge consists of three 150‐foot spans and is 32 feet wide.
The deck consists of an SPS 8‐25‐8 deck that spans transversely 6’‐3 ¼” between rolled steel
W27x114 beams.
The deck is made composite with the beams by shop welding the deck to the top flange of the
beams.
Deck splices use a combination of 1” diameter ASTM A325 bolts at 4” o.c. and a continuous
7/16” field groove weld.
The SPS deck was delivered from the shop with the girders already attached and was installed in
a single weekend.
Cross Section of Cedar Creek Bridge
Dawson Bridge: The Dawson Bridge, rehabilitated in 2010 in Edmonton, Canada is the only bridge with
SPS deck constructed without field welding.
The historic bridge was built in 1912 and
was originally designed to carry horse
drawn wagons and electric trains.
The 776‐foot long bridge has five steel
truss spans with varying span lengths
and a floor system with stringers and
floorbeams.
Replacement of the existing lightweight
concrete deck and timber sidewalks with
a lighter weight SPS 10‐25‐10 deck and
asphalt wearing surface was specified to
address structural deficiencies and
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increase the capacity of the trusses. The new deck spans transversely 6’‐2” between new
W18x50 stringers that range in length from 16’‐8” to 17’‐9”. The asphalt thickness varied from
1 ½” at the shoulder to 4” at the crown.
Project included a risk control plan for the SPS deck that consisted of:
o Background research of available literature on SPS deck systems,
o Site visits to existing bridges with SPS deck systems and interviews of bridge authorities,
o Development of a new all‐bolted SPS splice connection and full‐scale laboratory fatigue
testing of the new deck connection,
o Enhanced quality control during fabrication and construction of the deck,
o Monitoring of the deck during service.
Retrofit of Orthotropic Deck Bridges: The steel orthotropic decks of several long span and movable
bridges have been retrofitted using SPS technology by field installing an elastomer core and new steel
top faceplate on top of the existing deck plate, which became the steel bottom faceplate. This solution
was used to stiffen the flexible deck plate and reduce deflections and fatigue stresses.
2.1.10 Florida Bascule Bridge Specific Solution
Deck Solution: Using the preliminary design methodology described above, the required deck solution
for a typical Florida bascule span would consist of an SPS 5‐30‐5 deck with an overall thickness of 1½”
and overall unit weight of 22 psf excluding perimeter bars, wearing surface, bolts and supplemental
supports. With these additional items, the overall unit weight of the deck system is approximately 28
psf.
Structural Modifications: In order to accommodate the SPS deck, the following modifications to the
bridge are required:
New stringers are recommended to:
o Facilitate shop drilling bolt holes for the deck connections, which significantly reduces
the field work (i.e. match drilling the holes).
o Provide a clean, smooth top flange that yields a more uniform bearing and faying
surface.
o Eliminate pitting from previous surface corrosion that retains moisture and is conducive
to corrosion development.
o Eliminate need to exercise care in removing the existing steel open grid deck and
corresponding extensive grinding of stringer top flanges to remove residual weld and
base metal, which greatly reduces construction duration.
o Yield higher quality stringers.
o Permit optimization of the floor system with elimination of some stringers. The new
stringers can be spaced anywhere from 4’‐0” to 6’‐0” on center with this deck solution.
The same SPS deck solution can be used for significantly varying stringer spacing
because of the characteristics of the load distribution (i.e. wider stringers spacing yields
greater width of SPS deck that acts to resist and distribute the load). The new rolled
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steel stringers will likely be deeper than the existing stringers to accommodate the clip
angle end connections to the floorbeams. It may be possible to utilize a slightly lighter
stringer with more efficient section properties, that is composite with the deck, and/or
that utilizes higher yield strength (i.e. Grade 50 vs. Grade 36 steel), where possible.
The rack frames supporting the concrete filled deck (bridges with Hopkins frame drive
machinery) require their top flanges be raised, which can be achieved by using bolted flange
angles with longer vertical legs.
Removal of spacer bars from the top of the existing floorbeams and main girders is not required.
Minor modifications to the counterweight including saw cutting and grouting at the transition to
the SPS deck.
Deck Connection Details: The deck will be bolted to the top flange of the new stringers. At the main
girders, the deck will be bolted to new steel supports bolted to top flange. For existing riveted, built‐up
main girders, the new supports can utilize high strength bolts and the existing holes for the top flange
rivets. The new supports can also be field welded to the top flange of the main girders; however,
because the main girders are fracture critical elements, this approach introduces more risk and will
require weld procedure specifications (WPSs) in accordance with AWS D1.5 Bridge Welding Code,
Fracture Control requirements.
SPS Panel Deck Connection Details
The SPS deck for each leaf will extend from the front of the counterweight to the tip of the leaf (i.e. the
SPS deck will replace both the steel open grid and concrete filled grid decks) and will extend the width of
the roadway from curb to curb. In order to minimize the number of panel splices, which add significant
weight to the deck, the SPS panels will generally by oriented with the long dimension parallel to the
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roadway centerline with the panels spliced over each stringer or possibly every other stringer. The
panels can be made of a length where only one or two transverse splices are required. The volume of
the elastomer core and/or shipping and handling generally govern the length of the panels.
Panel Splice Details: IE has developed several SPS panel splice‐connection details, with the preferred
and recommended detail consisting of a combination of field bolting and welding. The connection
serves the dual purpose of connecting the SPS deck to the supporting steel beams and splicing the
panels together to provide continuity. This connection also is used to make the deck composite with the
supporting steel beams.
The bolted portion of the connection utilizes a countersunk bolt in a slip‐critical connection to create a
slush deck top surface that can accept a thin, lightweight wearing surface. Although, AASHTO LRFD
Bridge Design Specifications do not recognize the use of countersunk bolts in a slip‐critical connection,
the bolts can be fully tensioned using turn‐of‐nut method, which produces pre‐compression across the
faying surfaces needed to resist slip.
SPS Deck Panel Splice Detail
The restraint from the bolted connection can introduce significant residual tensile stresses if welding is
performed after bolting. Residual tensile stresses are additive to the tensile fatigue stresses, and may
reduce fatigue life of the steel connection. As such it is recommended that the panels be bolted after
welding is performed.
In some applications, this detail has permitted water to enter the elastomer cavity through poorly
seated countersunk bolts. The water froze during cold winter conditions resulting in failure of the
panels. Although there is a lower risk of freezing in Florida, water in the elastomer cavity presents a
potential concern with corrosion.
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Wearing Surface: SPS deck requires a lightweight, skid resistant wearing surface that bonds well and
protects the steel top plate from corrosion. Available wearing surfaces that meet these requirements
include:
Thin epoxy polymer wearing surface with:
o Several manufacturers with similar products that permits competitive bidding
opportunities,
o Unit weight of 3 to 4 psf for two‐layer system with ¼” total thickness,
o Good skid resistance (0.8 to 0.9 friction coefficient),
o Shop application of large sections and field touch‐up at welded joints,
o Ability to easily replace and repair surface,
o Significant experience in similar applications, but
o Limited service‐life (10 to 15 years) requiring period removal and reapplication.
Hot‐sprayed aluminum oxide grit (e.g. SlipNOT) with:
o Unit weight of 0.5 to 1.0 psf,
o Good skid resistance (0.8 to 0.9 friction coefficient),
o Shop application, but
o No experience as permanent roadway surface although limited experience as temporary
roadway surface in small areas (i.e. used on small plates to temporarily cover holes in
roadway),
o Additional research required to verify durability and long‐term skid resistance,
o Currently no support from supplier to re‐apply in field; however, this could change in
the future or another technology may be developed.
(See Section 4 on Wearing Surface Evaluation for more specifics).
Weight and Span Balance Requirements: The total weight of the required SPS deck and associated
perimeter bars, splice plates, bolts, main girder supports, and wearing surface is significantly heavier
than the weight of the typical existing deck to be removed. A deck that is heavier than the existing steel
open grid deck will also require additional counterweight ballast, equal to two to three times the net
increase in weight forward of the trunnion, to balance the leaf.
Limited capacity of the trunnion assemblies, limited available space in and around the counterweights,
and limited capacity of the main girders typically limit the total increase in weight that can be
accommodated.
There are often opportunities to offset some of the additional weight by replacing other components
with lighter components (although this unnecessarily increases the required modifications to the bridge
and cost of the project) including:
Replacement of the concrete filled portion of the deck with the proposed lightweight solid deck
will reduce the overall weight of the deck. However, because this deck is located close to the
trunnion, with more of the deck located back of the trunnion, the replacement does not
significantly reduce the required additional counterweight ballast.
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Replacement of the stringers with lighter, more efficient sections and/or reduction in the
number of stringers.
Replacement of steel sidewalk grating with lighter aluminum sidewalk plate or planking.
Replacement of the steel sidewalk support members and cantilevered bracket bracing members
with aluminum members.
Replacement of steel curbs and/or median with ones made from aluminum.
Replacement of steel bridge railing with lighter crash tested aluminum railing (e.g. Edgerail).
2.1.11 Costs
Construction Costs: The cost of the SPS deck system is anticipated to be significantly higher than the
cost to replace steel open grid roadway flooring (i.e. approximately two times the cost). The cost can
vary due to a number of factors and depends on the modifications required to fully implement the SPS
deck system. This anticipated work includes a number of items including:
Removal and disposal of the existing steel open grid and concrete filled deck,
Fabrication and installation of the new SPS deck panels,
Replacement of the stringers including end connections,
Removal of the main girder spacer bars and installation of new supports including replacement
of some of the top flange rivets with high strength bolts or field welding the supports,
Installation of the wearing surface,
Minor modifications to the counterweight including saw cutting and grouting to accept the SPS
deck,
Addition of ballast (e.g. adjustment blocks, concrete and/or steel ballast) secured to the
counterweight,
Span balance including detailed balance calculations, and instrumentation and recording of the
balanced condition before and after the work,
Adjustment of the live loads shoes in conjunction with the deck alignment,
Adjustment of the span locks in conjunction with the live load shoe adjustments,
Possible modification of the top of the rack frames (bridges with Hopkins frame drive systems
and where the rack frame supports the deck),
Possible incidental work to offset the increased weight including replacement of sidewalk
grating, sidewalk supports, bridge railing, curbs and/or medians with lighter members,
Possible retrofit work to the trunnion assemblies to increase capacity including new trunnion
bearing bushings with higher strength bronze material or spherical roller bearings,
Traffic control,
Mobilization work.
Maintenance Costs: The cost to maintain the SPS deck is anticipated to be similar to that of the steel
open grid roadway flooring. Many maintenance activities will be eliminated or significantly reduced,
while other maintenance activities will be added.
Reduced maintenance activities include:
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Reduction in the frequency of required cleaning and painting of the bascule leaf steel, as the
solid deck better protects these elements,
Elimination of the need to periodically repair broken steel open grid attachment welds,
Elimination of need to periodically repair cracked secondary and tertiary grid bars,
Elimination of the need to periodically improve skid resistance of steel open grid (e.g.
scarification of top surface),
Reduction in the future replacement of the deck.
Added maintenance activities include:
Periodic repairs or replacement of the wearing surface (e.g. thin epoxy polymer wearing
surface),
Possible more frequent replacement of trunnion bearing bushings due to heavier loads on
bearings.
Salvage Cost: The salvage value for SPS deck will be relatively low with limited scrap value for the steel
in the panels. Although many of the Florida bascule bridges are of a similar configuration, it will be
difficult to remove the panels from one bridge and relocated them to another bridge without damaging
the panels because of the welded connection and the somewhat sensitive bond between the elastomer
and the steel faceplates.
Design Cost: The design cost is anticipated to be significantly more than that for steel open grid deck due
to the need to perform inelastic, non‐linear, finite element analysis for each design to achieve the
lightest possible weight solution. In addition, because the SPS deck details will be initially unfamiliar to
the bridge design community, the cost of the plans production will also be higher, until the design
community becomes more comfortable with the design and details, develops design skills and work
product (plans and calculations) that can be adapted for use on multiple projects.
Inspection Cost: The inspection cost may be slightly higher than that required for replacement with steel
open grid deck, at least initially, as the construction community becomes more comfortable with the
quality control requirements for this new type of deck system and the unique materials. The shop
fabrication and welding inspection and field bolting and welding inspection are anticipated to be slightly
more than that for replacement with steel open grid deck.
2.1.12 References
Martin, James D. (2005). Sandwich Plate System Bridge Deck Tests M.S. Thesis, Virginia Polytechnic
Institute and State University, Blacksburg.
Lui, G.C., Alexander, S.D.B. (2007). “Fatigue of Steel Plate – Elastomer Composite Beams,” Structural
Engineering Report No. 274, University of Alberta, Edmonton, Alberta.
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Boggs, Joshua T. (2008). The Performance and Behavior of Deck‐to‐Girder Connections for the Sandwich
Plate System (SPS) in Bridge Deck Applications, M.S. Thesis, Virginia Polytechnic Institute and State
University, Blacksburg.
Zhou, Feng. (2008). Ultimate Strength of Clamped Steel‐Elastomer Sandwich Panels under Combined In‐
plane Compression and Lateral Pressure, PhD Dissertation, Virginia Polytechnic Institute and State
University, Blacksburg.
Little, J., Grondin, G.Y., Alexander, S.C.B. (2007). Sandwich Plate System Under In‐Plane Load and
Uniform Lateral Pressure, Structural Engineering Report No. 267, University of Alberta, Edmonton,
Alberta.
Harris, D.K. (2007). Lateral Load Distribution and Deck Design Recommendations for the Sandwich Plate
System (SPS) in Bridge Applications, PhD Dissertation, Virginia Polytechnic Institute and State University,
Blacksburg.
Kennedy, S.J., Murray, T.M. (2004). Ultimate Strength of an SPS Bridge – The Shenley Bridge, Quebec,
Canada, Paper Presented for Presentation at the September 19‐20 Session of the 2004 Annual
Conference of the Transportation Association of Canada, Quebec City, Quebec.
Kennedy, D.L.J., Ferro, A., Dorton, R.A. (2005) Tentative Design Rules for Innovative Bridge Decks
Comprising Sandwich Plate System Panels, Paper Presented for Presentation at the Innovations in Bridge
Engineering (A) Session of the 2005 Annual Conference of the Transportation Association of Canada,
Calgary, Alberta.
Intelligent Engineering (IE). (2010). Company Profile, http://www.ie‐sps.com/about.html?sku=110
Accessed February 1, 2012.
Intelligent Engineering (IE). (2012). SPS the Sandwich Plate System, http://www.ie‐
sps.com/index.html?sku=0 Accessed February 1, 2012.
Brooking, M.A., Kennedy, S.J. (2003). The Performance, Safety and Production Benefits of SPS Structures
for Double Hull Tankers, Intelligent Engineering Ltd., Ottawa, Ontario.
Freitas, S.T.F., Kolstein, H., Bijlaard, Frans. (). Sandwich System for Renovation of Orthotropic Steel Bridge
Decks.
Lima, K., Kanji, S., DiBattista, J. (2011). Innovative Rehabilitation Gives new Life to a 100‐Year‐Old Steel
Truss Bridge, Paper Presented at Bridges – Successes: Let’s Build on Them Session of the 2011 Annual
Conference of the Transportation Association of Canada, Edmonton, Alberta.
Paultre, P., Chaallal, O., Proulx, J. (1991). Bridge Dynamics and Dynamic Amplification Factors – A Review
of Analytical and Experimental Findings.
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2.2 ALUMINUM ORTHOTROPIC DECK
2.2.1 Description
Aluminum alloys have much to offer for bridge deck applications, and continue to be used, primarily
overseas, where their lightweight, high strength‐to‐weight ratio and excellent corrosion resistance
satisfy service requirements. Aluminum is manufactured by an extrusion process, which permits highly
customized sections that can be optimized for a given application. The lack of widespread use of
aluminum, despite the structural and maintenance advantages, is primarily due to the high initial cost of
the material.
Today, there is a limited number of bridge deck extrusions that have been developed and are available
for use. SAPA Group currently offers two extruded aluminum orthotropic bridge deck products that have
been developed and used on bridges in limited use worldwide including installations on bascule bridges:
SAPA 100, 4‐inch (100 mm) deep, 11‐or 12‐inch wide plank‐like section, connected with adjacent
section with tongue and groove connection.
SAPA R‐Shape, 8‐inch deep, 12‐inch wide section fabricated into wider panels by friction‐stir
longitudinal weld at both top and bottom flanges.
(a) (b)
Available extruded deck sections (a) Sapa 100 (b) Sapa R‐shape.
Material: A great number of aluminum alloys might be chosen for bridge deck construction, but those
most highly recommended and used currently because of their superior combination of strength,
corrosion resistant, and overall ease of fabrication are alloys of the 5XXX series are used for the plate
components, and the 6XXX alloys are used for the extruded shapes. Alloy 6063 is a particular favorite for
the extrusions where complex and/or hollow sections are used.
Deck systems typically include a thin epoxy polymer bridge deck overlay.
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2.2.2 Product Development and Corporate Information
There is a long history (nearly 80 years) on the use of aluminum as a material for bridge structural
members and bridge deck in limited use. The first practical use of aluminum in bridge applications can
be traced to 1933 when the timber and steel floor system in the Smithfield Street Bridge in Pittsburgh,
PA, was replaced by an aluminum deck. The change was made to reduce the dead load and increase the
live load capacity. The new deck was a riveted orthotropic deck. The aluminum deck structure carried
two tracks of electrified trolley cars and two lanes of motor traffic and was the major artery for traffic in
Pittsburgh. The 1933 deck structure remained in service without problems for 34 years. In 1967 the deck
was upgraded with a new welded aluminum orthotropic deck with increased load carrying capacity for
larger, heavier trolleys and trucks. This aluminum deck remained in service for 26 years without
problems until 1993 when it was replaced by a steel deck, due to short‐term economics, not life‐cycle
cost. There were also seven highway and rail bridges in the United States and ten in Europe constructed
with aluminum superstructures from the 1940’s through the 1960’s.
SAPA Group, the world’s largest aluminum profile company, based in Sweden and with numerous
manufacturing plants throughout North America, has significant experience with aluminum bridge deck
technology that has evolved from 43 years of experience. SAPA currently owns patents for aluminum
orthotropic bridge deck technology that has been used on 70 bridge projects in Europe since 1987 and
more than 110,000 square feet of aluminum bridge deck worldwide. More information regarding SAPA
can be found at www.sapagroup.com.
SAPA 100 Section: The SAPA 100, 4‐inch deep extrusion is manufactured specifically for bridge deck
applications and includes both 11‐inch and 12‐inch wide planks. The product has not been used in the
United States, but SAPA reports nearly 50 installations in Europe along with a similar product, SAPA 50,
2‐inch deep plank not considered in this study. The individual planks are placed on top of the support
framing, side‐by‐side and connected to each other at the top of the planks with tongue and groove
connection. The attachment of the plank to the supporting framing is by way of clamps that engage a lip
at the bottom plate between the planks, which makes the bolts accessible. A thin, epoxy‐polymer
wearing surface is typically applied to the top of the planks.
The unit weight of planks is approximately 14 psf, excluding fasteners, wearing surface, and other
appurtenances. With these additional items, the overall unit weight of the deck system is approximately
18 psf, which is very similar to the unit weight of many existing steel open grid decks.
SAPA 100 Aluminum Plank Deck System.
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Elements of this deck system were tested and evaluated in 2009 as part of a Florida Department of
Transportation funded research project to identify a viable alternative deck system for steel open grid
deck. The study performed load testing of individual planks under simulated AASHTO vehicular loading
to evaluate structural performance of the planks. The load testing was compared with finite element
analysis. The research also load tested the capacity of the tongue and groove connection between the
planks and the capacity of the attachment hardware. The report concluded that this deck system was a
feasible alternative to steel open grid roadway flooring.
Despite the promising performance of elements of this deck system, the research did not consider a
number of important factors:
The relatively flexible Florida bascule leaf structures experience significant cantilever deflections
(i.e. significant tension and corresponding elongation of the main girder top flange) both during
operation and with vehicular traffic on the span. The large number of transverse tongue and
groove joints between the planks will open and close under these deformations. This
movement will likely result in reflective cracking of the thin epoxy polymer wearing surface at
the joints. This will also permit moisture to penetrate these joints resulting in potential
corrosion concerns of the steel members below.
Although the clamp‐type connection hardware performed well in laboratory static load testing,
there are potential long‐term serviceability concerns with this type of connection. The relatively
flexible Florida bascule bridges are known to experience significant vibrations from traffic
loading and there are concerns that the clamp‐type connection hardware will loosen under
these vibrations. Similar clamp‐type hardware has been used on other aluminum products on
bascule bridges including sidewalk grating and pedestrian railings and has experienced loosening
of the hardware. The clamp‐type connection requires tight fabrication tolerances and nearly
perfect fit‐up to ensure that the parts are drawn into tight contact. Small gaps can result in
movements between the parts that reduce the bolt pre‐load and allow the nut to loosen over a
period of time from vibrations. Bolted connections that draw the faying surfaces of the two
parts tightly together and that can be fully tensioned have demonstrated better performance.
The structural analysis and design for this deck system is complex and there currently are no
simplified, closed‐form equations available to assist designers in estimating wheel load
distribution to the planks. Without simplified equations, finite element analysis is the only
practical available tool to estimate this load distribution. The use of finite element analysis to
design a deck for each bascule bridge rehabilitation project that requires deck replacement adds
significant engineering cost to the project and is generally not considered practical.
Although promising in many respects, SAPA 100 deck system is not ready for immediate implementation
as an alternative deck system for steel open grid deck on existing bascule bridges in Florida. More
research is required to verify the performance of wearing surface and clamp‐type connections in this
application, and a simplified, closed‐form, set of engineering equations are needed to compute the
wheel load distribution to the planks, before this product can be recommended. In addition, other
aluminum orthotropic bridge deck products are available that address the above concerns. As such, this
product has not been further evaluated in this study.
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SAPA R‐Section Deck: Sapa R‐Section, 8‐inch deep extrusions were developed and are manufactured
specifically for bridge deck applications. The 12‐inch wide extrusions are fabricated into wider panels by
friction‐stir welding the extrusions together. The deck system also includes a half‐width, special
extrusion that accommodates a bolted splice between panels that is flush with the top surface of the
deck. Recent advancements in friction‐stir welding allows for faster and more efficient fabrication of
panels. Friction‐stir welding also introduces significantly less heat than traditional arc welding that can
weaken the base metal.
This extrusion was originally developed by Reynolds Metal Company under trade name Alumadeck.
Reynolds Metal Company was later acquired by Alcoa, Inc. and then SAPA Group acquired the
technology and fabrication facilities from Alcoa. This deck system is currently recognized as Sapa R‐
Section.
The unit weight of the extrusions is approximately 21 psf, excluding wearing surface, connection
hardware, splice plates, and other appurtenances. With these additional items, the overall unit weight
of the deck system is approximately 25 psf.
Friction‐stir Welded Aluminum Sapa R‐Section Panel.
Attachment of the SAPA R‐Section extrusion to the steel framing is achieved by bolting through the
bottom plate of the extrusion. Because the panels are made continuous, the interior of the panels are
not directly accessible for bolting. As such, SAPA has developed a procedure to insert the bolts.
A long aluminum angle (approximately half the length of the panel) is fabricated with the bolts
secured to the horizontal leg.
The angle with the bolts is inserted in the open end of the panels between the panel web
members. The stiffness of the angle allows it to be manipulated from the end and permits the
bolts to be aligned with the pre‐drilled holes in the panels and supporting framing.
The openings between the panel web members must be parallel to the framing members in
order to use this procedure. The location of the supporting framing members must be located
and aligned such that the bolts can be connected to the flange. It is recommended that the bolt
holes in the panels and framing members be match drilled to ensure alignment.
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The head of the bolts are locked in to prevent twisting during bolt tightening by the vertical leg
of the angle. Bolts are tightened by turning the nut at the underside of the top flange of the
framing member.
2.2.3 Recent Bridge Installations
Virginia Department of Transportation implemented Alumadeck in two experimental bridge
rehabilitation projects in 1996:
Corbin Bridge: Rehabilitation of the historic Corbin Bridge in Huntingdon, VA included replacement of
the existing bridge deck with lighter weight aluminum deck to reduce dead load, preserve the historic
truss structure, and increase live load capacity.
Little Buffalo Creek Bridge: Replacement of the Little Buffalo Creek Bridge on SR 58 near Clarksville, VA
with a new bridge that included a lightweight aluminum deck was performed for research purposes.
Research included load testing and structural evaluation that compared theoretical and
measured static and dynamic response to vehicular loads. The research also investigated the
composite behavior between girders and deck, live load distribution to the girders, and deck
fatigue performance.
The bridge consisted of a 54’‐7¼” long single‐span structure with four steel girders and
Alumadeck bridge deck.
The deck panels were oriented with the longer dimension parallel with the roadway centerline
and made composite with the girders.
The Alumadeck performed well in both bridges and the observed behavior was close to that estimated
by theoretical calculations. The researchers concluded that Alumadeck is a feasible alternative to
concrete decks on fixed‐span bridges, where it is crucial to reduce the weight and improve live load
capacity.
(a) (b)
Virginia DOT Alumadeck Installations: (a) Corbin Bridge, (b) Little Buffalo Creek Bridge
Alan Road Bridge: Replacement of the superstructure on the Alan Road Bridge over Farmington River
near Sandisfield, MA by Massachusetts Department of Transportation in 2001, included a lightweight
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SAPA R‐Section bridge deck to minimize total weight of the structure, preserve the timber abutments,
and permit rapid construction to minimize the duration the bridge would be out of service.
The new superstructure (deck and girders) was fabricated off‐site as a single unit, shipped by
truck to the site, and installed on abutments using a single crane lift.
The bridge is a 53’‐3¾” long, single‐span structure with four steel girders and 889 square‐feet of
SAPA R‐Section aluminum deck.
The deck panels were oriented with the longer dimension parallel with the roadway centerline
and made composite with the girders.
MassDOT Sapa R‐Section Installation: Alan Road Bridge over Farmington River, MA
Although the SAPA R‐Section deck demonstrates tremendous promise, implementation of this deck on a
typical Florida bascule bridge presents a number of challenges that makes the deck less desirable. These
challenges are described below.
Significant modifications to existing Florida bascule bridges are required to accommodate a deck that is
3 inches deeper than the existing 5‐inch deep steel open grid deck. In order to accommodate this deck,
the roadway profile at the bascule span must be raised 3 inches which requires:
Adjustment of the approach span deck profile to match the raised deck on the bascule leaf by
lifting the end at the bascule pier by installing a 3‐inch thick fill at the flanking beam floorbeam
bearings,
Replacement of the bascule pier sidewalk or raising of the sidewalk by pouring a new sidewalk
slab on top of the existing sidewalk slab,
Raising the bascule leaf sidewalk by replacing the sidewalk support framing, curbs, sidewalk
grating, pedestrian railings, and span lock access hatches,
Raising the control house floor and doors, flooring, floor hatches, ladders, plumbing, control
desk, electrical penetrations, etc.
The span capability of the deck (up to 12 feet) would permit the deck to span longitudinally between
floorbeams and eliminate the stringers with new floorbeams added at mid distance between existing
floorbeams (i.e. at the location of the existing intermediate cantilevered brackets). The deck can also
span transversely across stringers at a wider spacing.
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An alternative to raising the roadway profile was also investigated, but was found to introduce too many
detailing concerns. The deck will have to be modified at the main girders, floorbeams and
counterweight girders with shallower extrusions (i.e. the deck thickness will have to step) with the
following concerns:
Steps in the deck thickness will introduce stress risers and numerous undesirable details.
There does not appear to be a practical solution to accommodate the stepping of the deck
thickness at both the floorbeams and main girders without introducing a significant number of
small pieces and corresponding number of additional joints and splices.
The typical deck connection details used by Sapa for this deck system will also not be practical.
The above concerns are applicable whether the deck is oriented with the extrusions parallel to the
roadway centerline or perpendicular to the roadway centerline.
The total weight of the SAPA R‐Section deck and associated splice plates, bolts, main girder supports,
and wearing surface is significantly heavier than the weight of the typical existing deck to be removed.
This also will require additional counterweight ballast, equal to two to three times the net increase in
weight forward of the trunnion, to balance the leaf. The additional weight may also overload the
trunnion assemblies, which have limited reserve capacity (see Trunnion Capacity Evaluation). There are
opportunities to offset the increase in deck weight with other modifications (although this unnecessarily
increases the required modifications to the bridge and cost of the project).
2.2.4 Florida Bascule Bridge Specific Solution
Deck Solution: In recognition of the significant advantages of aluminum orthotropic deck systems and
the need for a lightweight, solid deck product that can replace steel open grid deck on Florida bascule
bridges with minimal modifications, a 5‐inch deep version of the SAPA R‐Section, similar to the depth of
the 5‐3/16” deep steel open grid deck has been developed and evaluated for consideration. This product
is considered a derivative of already developed aluminum orthotropic deck designs. The proposed
alternative extrusion was developed, analyzed and evaluated by the research team in consultation with
SAPA consultants including Randy Kissell, lead author of Chapter 7 (Aluminum Structures) of the
AASHTO LRFD Bridge Design Specifications. Financial viability and product support has been discussed
with SAPA executives.
The alternative orthotropic deck design takes advantage of previous product development for the SAPA
R‐Section and Alumadeck including research, testing, engineering design, and latest advancements in
aluminum technology including friction‐stir welding. Because the proposed deck would be nearly
identical to the SAPA R‐Section deck, the majority of research previously prepared specifically for the
SAPA R‐Section (e.g. live load distribution, strength, fatigue, deflection, and composite behavior) would
still be valid for the new extrusion. Engineering calculations based on previous research for the SAPA R‐
Section verifies the adequacy of the proposed section. Additional testing of proposed alternative
connections to the supporting steel framing may be warranted.
The alternative extrusion is depicted below.
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Alternative 5‐inch Deep Aluminum Orthotropic Deck Extrusion
Analysis of this alternative extrusion yielded the following results:
The unit weight of the extrusions is approximately 17 psf, excluding wearing surface, connection
hardware, splice plates, and other appurtenances. With these additional items, the overall unit
weight of the deck system is approximately 21 psf.
Deck is designed to span transversely across stringers.
Span capability of the deck system is a maximum of 8’‐9” between stringers (governed by L/800
deflection limits.)
The deck system comfortably meets all AASHTO LRFD Bridge Design Specifications Strength,
Service (Deflection) and Fatigue Limit States (including newly revised and adopted provisions).
Design is generally governed by local stresses in deck top plate under wheel patch loads.
The deck is very stiff with very small live load deflections (i.e. approximately L/3000 for stringer
spacing typical for Florida bascule bridges).
The alternative extrusion appears to be more efficient than the SAPA R‐Section with lower
governing top plate localized stresses, despite the use of conservative load distribution and
structural support assumptions used to evaluate SAPA R‐Section. The lower stresses are due to
the use of the same top plate thickness as the SAPA R‐Section, even though there is a shorter
effective span between web members.
As discussed with SAPA, there may be opportunities to further optimize this alternative extrusion to
achieve additional structural efficiency and weight reduction.
The 5‐inch deep alternative extrusion maintains all of the advantages of the 8‐inch deep SAPA R‐Section
extrusion, but eliminates the significant disadvantages including:
The 5‐inch deep profile does not require raising the bascule span roadway profile and
corresponding substantial bridge modifications.
The weight of the deck is much closer to that of the existing steel open grid deck. As such, the
adjustments to the counterweight and additional load on the trunnions are minimized. The
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solution does not require other modifications needed to offset the increase in weight, not
otherwise required.
Structural Modifications: The following modifications to the bridge are required to implement the
aluminum orthotropic deck:
Existing stringers supporting existing steel open grid deck can be reused and remain as currently
configured. However, replacement of the stringers is recommended in order to:
o Facilitate shop drilling bolt holes for the deck connections, which significantly reduces
the field work (i.e. overhead match drilling these holes).
o Provide a clean, smooth top flange that yields a more uniform bearing and faying
surface.
o Eliminate pitting from previous surface corrosion that retains moisture and is conducive
to corrosion development.
o Eliminate need to exercise care in removing the existing steel open grid deck and
corresponding extensive grinding of stringer top flanges to remove residual weld and
base metal, which greatly reduces construction duration.
o Yield higher quality stringers.
o Permits optimization of the floor system with elimination of some stringers.
Existing stringers supporting the concrete filled steel grid deck over the machinery areas require
lowering by 2 inches to address difference in height between the 3‐inch existing deck and new
5‐inch deck.
The rack frames that support the concrete filled deck (bridges with Hopkins frame drive
machinery) require that the top flanges be lowered by removing and reattaching the top flange,
and trimming the top of the web.
Removal of spacer bars from the top of the existing floorbeams and main girders is not required,
but is recommended to eliminate unnecessary loose contact between the aluminum deck and
steel framing.
Minor modifications to the counterweight including saw cutting and grouting at the transition to
the aluminum deck.
Deck Connections: The deck will be bolted to the top flange of the new stringers. At the main girders,
the deck will be bolted to new steel supports bolted to top flange. For existing riveted, built‐up main
girders, the new supports can utilize high strength bolts and the existing holes for the top flange rivets.
The new supports can also be field welded to the top flange of the main girders; however, because the
main girders are fracture critical elements, this approach introduces more risk and will require weld
procedure specifications (WPSs) in accordance with AWS D1.5 Bridge Welding Code, Fracture Control
requirements.
An alternative deck connection detail is proposed to attach the aluminum orthotropic deck to the steel
framing using a blind installed internally threaded rivet type connection, a.k.a. Rivnut. Rivnuts were
originally developed and patented in the 1936 for use in the aircraft industry to connect thin elements
and make blind attachments. Advancements in Rivnut technology now include high‐strength and
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corrosion resistant materials that can accept ASTM A325 high‐strength bolts. Currently, the maximum
available size of high‐strength rivnuts is ½‐inch diameter; however, Bollhoff, the manufacturer of the
Rivnuts, has indicated that a custom ¾‐inch diameter can be fabricated.
Rivnut (Internally Threaded Rivet) Connection
The deck will be conservatively treated as non‐composite in sizing the supporting steel stringers, while
the number and size of connection fasteners will be determined by conservatively assuming that the
deck acts compositely with the stringers. Oversized holes in the steel members will be used to
accommodate thermal expansion with standard sized holes used at the center of thermal movement to
secure and maintain the alignment of the panels as the movement occurs and as the bridge raises and
lowers. Preliminary calculations for the strength of the composite connection indicate that ½‐inch
diameter bolts at 3¾ inches on center (i.e. four connectors per panel opening between the members)
will be adequate. Alternatively, ¾‐inch diameter bolts spaced at 7½ inches on center (i.e. two
connectors per panel opening between the web members) will also be adequate. Bolts throughout the
panels can be omitted intermittently due to detailing issues without concern.
Panel Splice Details: The aluminum deck for each leaf will extend from the front of the counterweight to
the tip of the leaf (i.e. the aluminum deck will replace both the steel open grid and concrete filled grid
decks) and will extend the width of the roadway from curb to curb. The transversely spanning panels can
be made in lengths up to approximately 40 feet. This will permit the panels to extend the full width of
the roadway for two‐lane bridges (typically 28 to 32 feet on most two‐lane Florida bascule bridges) and
half the width of the roadway for four‐lane bridges (typically 42 to 48 feet on most four‐lane Florida
bascule bridges) with an open joint between the two halves below the median. The panels can be made
shorter and in two halves to accommodate phased deck replacement where required to facilitate traffic
control.
Panel splices utilize a special half‐extrusion that is friction‐stir welded to the other extrusions along the
edges of each panel. When two adjacent panels are butted together, the special half‐extrusions
accommodate a bolted aluminum splice plate that fits in a recess in the top of the extrusions to splice
the panel top plate and maintain a flush deck surface. An aluminum splice plate is used on the
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underside of the panels to splice the bottom plate. The use of Rivnuts, similar to the deck connection, is
recommended to address the blind connection for the splice plates.
Possible Detail of 5‐inch Aluminum Deck Spanned Transversely Attached to Existing Stringers
Wearing Surface: The aluminum deck requires a lightweight, skid resistant wearing surface that bonds
to the aluminum top plate. Available wearing surfaces that meet these requirements include:
Thin epoxy polymer wearing surface with:
o Several manufacturers with similar products that permits competitive bidding
opportunities,
o Unit weight of 3 to 4 psf for two‐layer system with ¼” total thickness,
o Good skid resistance (0.8 to 0.9 friction coefficient),
o Shop application of large sections and field touch‐up at welded joints,
o Ability to easily replace and repair surface,
o Significant experience in similar applications, but
o Limited service‐life (10 to 15 years) requiring period removal and reapplication.
Hot‐sprayed aluminum oxide grit (e.g. SlipNOT) with:
o Unit weight of 0.5 to 1.0 psf,
o Good skid resistance (0.8 to 0.9 friction coefficient),
o Shop application, but
o No experience as permanent roadway surface although limited experience as temporary
roadway surface in small areas (i.e. used on small plates to temporarily cover holes in
roadway),
o Additional research required to verify durability and long‐term skid resistance,
o Currently no support from supplier to re‐apply in field; however, this could change in
the future or another technology may be developed.
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(See Section 3 Wearing Surface Evaluation for more specifics).
Weight and Balance Requirements: Due to small differences in the unit weight of the existing deck and
new deck, the counterweight will require some adjustment. Because the weight of the new deck is very
similar to the typical steel open grid deck, adjustments can likely be made by adjusting the balance
blocks. Other modifications to offset the weight are not anticipated.
2.2.5 Functionality and Safety
Load Capacity: An aluminum orthotropic deck designed to governing stress limits will have
corresponding load carrying capacity in excess of that required to support AASHTO LRFD HL‐93 Live
Loads. The unit weight of the proposed aluminum deck will be close to that of the existing steel open
grid deck, and thus there will be no reduction in capacity of the bascule span members.
Rideability: The aluminum orthotropic deck and the corresponding applied wearing surface will provide
a smooth, continuous riding surface with a surface roughness comparable to asphalt or concrete
pavement. Because the aluminum orthotropic deck has greater stiffness than the existing steel open
grid deck, deflections and vibrations will be significantly reduced, which will further improve the quality
of the ride.
Skid Resistance: Skid resistance from the applied wearing surface will be similar to that of asphalt
pavement. See Section 3 Wearing Surface Evaluation.
Noise: The solid surface of the aluminum orthotropic deck is anticipated to reduce noise generated by
tires in contact with the deck relative to steel open grid deck. However, the hollow cells of the deck may
still generate some resonance due to vibration of the deck thin web members.
Bicycle Safety: The aluminum orthotropic deck provides a solid riding surface for the roadway and
shoulders with small longitudinal open joints (less than ½” wide) located immediately adjacent to the
curbs or barriers, which will greatly improve bicycle safety. Transverse deck joints between the two
bascule leaves and between the bascule span and bascule pier will range from ¾” to 1½” in width, but
should not be a concern for bicyclists.
2.2.6 Durability and Service Life
Service Life: It is anticipated that the aluminum orthotropic deck system will provide a minimum service
life that exceeds the remaining life of a typical existing bascule bridge (i.e. 30 to 40 years). Installations
of aluminum deck in similar coastal environments in Europe confirm that this service life can be
achieved.
Fatigue Resistance: Significant research on fatigue of aluminum orthotropic decks and conservative
design practice for fatigue provides that confidence that fatigue will not be a concern. Advancements in
aluminum welding technology (e.g. friction‐stir welding) yields significant improvements in fatigue
resistant at the welded joints, although, this increased fatigue resistance is conservatively neglected in
current design practice.
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Corrosion Resistance: Aluminum has been commonly been used on bascule bridges in Florida for
various components including sidewalk surfaces and pedestrian railings without significant corrosion
concerns, where appropriate materials and detailing practices are used. Aluminum can be subject to
several types of corrosion that are either inconsequential or that can easily be mitigated.
Open Air Corrosion: Uncoated aluminum provides excellent corrosion resistance primarily because
aluminum spontaneously forms a thin but effective oxide layer that prevents further oxidation.
Aluminum oxide is generally impermeable and, unlike the oxide layers on many other metals, it adheres
strongly to the parent metal. If damaged mechanically, aluminum oxide layer repairs itself immediately.
The aluminum oxide layer is generally stable in the pH range 4 to 9, which is the expected pH in the
marine environment.
The corrosion of metals in the open air depends on the duration of wetness and the composition of the
surface electrolytes. The duration of wetness refers to the period during which a metal surface is
sufficiently wet for corrosion to occur and it is normally considered to be the period when condensation
occurs (i.e. duration when relative humidity exceeds 80% and metal surface temperatures are below the
dew point temperatures) which is usually during nighttime hours. Condensation does not typically form
during daylight hours and condensation from nighttime hours usually evaporates quickly after the sun
rises. Surface wetness can also occur during periods of fog and splashing from waves, although the deck
on most bascule bridges is usually well above the splash zone. The hollow interior of the aluminum
orthotropic deck can be sealed such that there is not a significant change in humidity.
In marine environments, surface corrosion can result in superficial surface pitting, that is generally
considered inconsequential. The Swedish Corrosion Institute has carried out field exposure tests in a
number of environments and for numerous untreated metals. The average loss in thickness (measured
by pit depth) of uncoated aluminum plate in marine environments was found to be less than 10 μm
(0.01 mm) per year.
The details of the aluminum orthotropic deck, with a flat, horizontal bottom are generally such that
there will be no standing water and thus the presence of an electrolyte is minimized. The thin epoxy
polymer, wearing surface provides additional corrosion protection for the top surface of the deck and
the high stiffness of the aluminum orthotropic deck provides greater confidence that the wearing
surface will not be breached.
Galvanic Corrosion: Galvanic corrosion can occur when dissimilar metals are in metallic contact in the
presence of an electrolyte (e.g. wet coastal atmosphere). In the presence of a liquid, a battery cell is
created, allowing current to flow with corrosion occurring at the anodic component of the cell. The
least noble metal in the combination becomes the anode and corrodes, while the more noble of the
metals becomes the cathode and is protected against corrosion. In the aluminum‐steel combination,
aluminum is less noble than steel and thus is expected to corrode and sacrifice itself for the steel.
Although, galvanic corrosion from the direct contact of uncoated aluminum with steel is a known to
occur, this issue is easily mitigated. Where dissimilar metals are used in combination, galvanic corrosion
can be prevented by electrically insulating the two materials. Painting the steel is considered an
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adequate insulator and is a practical solution. The Aluminum Design Manual specifies that a steel paint
system consisting of a zinc primer and intermediate and finish coats containing aluminum, as is the case
for typical Florida DOT preferred coating systems, will provide adequate separation to prevent corrosion
due to dissimilar metals. The Aluminum Design Manual also specifies that aluminized, hot‐dip
galvanized or electro‐galvanized steel placed in contact with aluminum need not be painted.
Special care should be taken in the selection of the fasteners and/or fastener coatings to avoid galvanic
corrosion. There are a number of available steel fastener materials that have been effectively used with
aluminum on Florida bascule bridges (e.g. Type 316 stainless steel and hot dip galvanized bolts, nuts and
washers). Stainless steel is more noble than the aluminum and thus the fasteners are not expected to
corrode; however, the less noble aluminum may experience localized corrosion adjacent to the
fasteners in severe conditions, although this has not been common on other aluminum materials on
Florida bascule bridges. Galvanized steel fasteners contain zinc, which is less noble than aluminum and
will protect the aluminum; however, the oxidation will eventually exhaust the zinc coating and the
fastener will have a limited service life. Galvanic corrosion is minimized when the more noble
component has a small surface area relative to the less noble component. Because the fasteners have a
small surface area, compared to the aluminum deck, galvanic corrosion is less of a concern.
Crevice Corrosion: Crevice corrosion can occur in narrow, liquid‐filled crevices (e.g. the joints between
panels). Water on the surface adjacent to joints is drawn, through capillary action, into the crevices
between the metal surfaces. Use of sealing compounds between components can prevent moisture
from entering the crevices and minimize crevice corrosion. Pre‐compression of the plates within the
joint from proper bolt tightening will also act to seal the crevices.
Impact Resistance: The 3/8” minimum thickness of the top flange plate and the high stiffness of the
aluminum orthotropic deck are anticipated to yield relatively good impact resistance in the event that a
vehicle overturns and impacts the deck surface.
Fire Resistance: Similar to steel members, aluminum loses strength and stiffness when exposed to high
temperatures. However, the threshold temperature where aluminum is affected by heat is lower than
that of steel (400 to 600 degrees F for aluminum compared to 900 to 1100 degrees F for steel).
Similar to steel members, aluminum orthotropic deck is likely to survive short duration fires and/or fires
with lower temperatures. Because the loss of strength is time‐dependent, panels may provide limited
structural support for loads on the deck during a fire (e.g. the vehicle on fire, emergency response
vehicles and personnel). If the deck panels lose strength during these events, the steel framing below
may steel provide some support to contain vehicles.
Only a substantial heat source, such as that from a roadway accident with ignited localized fuel spill, is
expected to threaten the integrity of aluminum deck.
Thermal Expansion: The difference in coefficients of thermal expansion between aluminum and steel
(12.8 x 10‐6/°F and 6.5 x 10‐6/°F respectively) and the restraining effects from bolting the deck to the
steel framing and the stiffness of the steel framing must be considered in detailing the deck. In addition,
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as the aluminum deck will have more direct exposure (i.e. the aluminum deck will be directly exposed to
the sun, while the steel framing will be shaded by the deck) and aluminum has higher thermal
conductivity (i.e. the aluminum changes temperature at a faster rate than steel), the temperature of the
aluminum is anticipated to be significantly different than the temperature of the steel. Differential
movements between the two materials is anticipated to be significant (i.e. differential movements will
exceed 3/8” from counterweight to leaf tip and 1/8” to 1/4” from curb to curb on a typical two‐lane and
four‐lanes Florida bascule bridges, respectively). Because of the magnitude of these differential
movements, details for attaching the deck will need to accommodate the movement and prevent
restraint that would develop large forces in the deck and steel framing members. More accurate
assessment of the differential temperature will need to be determined during design.
The difference in thermal expansion can be addressed as follows:
Deck panels will extend transversely the full width of the roadway, from curb to curb, for a
typical two lane Florida Bascule bridge.
Deck panels will extend transversely half the width of the roadway, with an expansion joint in
the middle of the roadway, beneath the median for a typical four lane Florida bascule bridge.
The panels will be spliced such that they are continuous within each floorbeam bay in the
longitudinal direction, with intermediate expansion joints between the panels located over each
of the intermediate floorbeams. Maximum thermal movements are estimated to be less than
1/32‐inch within a floorbeam bay.
Oversized holes in the steel members will be used to accommodate thermal expansion with
standard sized holes used at the center of thermal movement (i.e. at the center of the
floorbeam bay) to secure and maintain the alignment of the panels as the movement occurs and
as the bridge raises and lowers. The panels will bear on 1/8‐inch thick, high Durometer (70‐90)
neoprene pads
Expansion joints between panels and at the curbs can consist of low cost, low maintenance low
modulus silicone joint sealant with backer rods installed against the vertical plates at the edge of
the panels or neoprene strip seals secured to the panel special end extrusions.
Chemical Resistance: Aluminum provides similar resistance to chemicals as steel elements on the
bridge. The protective properties of the natural oxide layer, yields good resistance to many chemicals.
Low or high pH values (less than 4 and more than 9) lead to the oxide layer dissolving and, consequently,
rapid corrosion of the aluminum. Inorganic acids and strong alkaline solutions are thus very corrosive for
aluminum. The wearing surface provides limited protection of the aluminum from chemicals.
Ultraviolet (UV) Light Resistance: Aluminum is not subject to degradation from UV light and there are no
coatings required for the deck system that can degrade.
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2.2.7 Design and Analysis
Design Considerations and Approach: Design of the aluminum orthotropic deck will be based on
AASHTO LRFD Bridge Design Specifications. Design provisions were recently submitted by the aluminum
industry to AASHTO for consideration and adoption. The deck is designed for AASHTO LRFD Strength I,
Service I (deflections) and Fatigue I Limit States (infinite fatigue life). Similar to steel orthotropic decks,
the deck is evaluated for three different structural systems:
System 1: Global Stresses (Strength and Fatigue) in the deck due to composite action with
supporting steel framing are evaluated. Although the steel framing will conservatively be
designed neglecting composite behavior, it is anticipated that the deck will exhibit some
composite behavior due to friction and resistance in the bearing pads between the deck and
stringers or main girders. As such, the fasteners used to connect the deck to the supporting
members will be evaluated for the composite action.
System 2: Global Stresses (Strength, Fatigue and Deflection) in the deck due to flexure between
the stringers are evaluated. Calculations for load distribution to determine flexural moments in
the aluminum orthotropic deck panels are based on classical orthotropic deck theory. The load
distribution equations have been corroborated by testing of SAPA R‐Section panels performed
by Virginia Department of Transportation.
System 3: Local Stresses (Strength and Fatigue) in the deck top plate due to wheel patch loads
are evaluated.
Calculations can be performed with closed‐form equations using spreadsheets (e.g. Excel, MathCAD,
etc.).
The design of the deck for typical stringer spacing on Florida bascule bridges is governed by System 3
local fatigue stresses. Deflections corresponding to stringer spacing found on typical Florida bascule
bridges are very small (approximately L/3000). The maximum span capability (i.e. stringer spacing) of
the deck is 8’‐9” and is governed by allowable deflection limits (L/800).
2.2.8 Constructability
Fabrication: The aluminum orthotropic deck panels and other components (e.g. splice plates, end plates,
joint plates, and other appurtenances) will be fabricated at an aluminum fabrication plant. The
extruded sections will be cut to length and welded together using friction‐stir welding to create panels.
The panels will then be mated up to the supporting stringers and main girder support angles in an
inverted assembly layout (i.e. the panels and stringers oriented upside down) to permit match drilling of
the holes for the connections and splices. The Rivnuts will then be installed in to the panels. The
wearing surface may also be shop applied to the panels and deck top splice plates.
Tolerances on panel length, width, camber, and flatness will generally be similar to that of steel open
grid deck. Tighter tolerances on panel sweep and squareness are needed to ensure proper fit‐up of the
panels at the splices and because the greater lateral stiffness of the panels will not permit adjustment in
the horizontal plane of the panels. The use of standard oversized holes in top flange of the stringers
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and main girder supports will assist in accommodating small differences between shop and field
alignment.
Field Installation: The existing steel open grid and stringers will be removed. The main girder and
floorbeam spacer bars will also be removed and the rack frames and counterweight girder top flanges
modified as required. The new stringers and main girder support members will be installed. Final
drilling of the holes in the webs of the floorbeams for the stringer connection angles will be performed
after the panels are aligned to the stringer top flanges. Shims between the stringer connection angles
and floorbeam webs will be provided for adjustment. Removal of the existing rivets and final drilling of
the holes in the horizontal legs of the new supports at the main girder top flanges (or field welding of
the supports if permitted) will be performed with the panels aligned to the supports.
Specialized Inspection: Friction‐stir welding, Rivnut fasteners, and thin epoxy polymer wearing surfaces
(or hot‐spray applied aluminum oxide grit wearing surface if permitted) are less common to the bridge
industry and thus inspection of this construction will, at least initially, be considered specialty in nature.
Fabrication of the aluminum deck will require aluminum fabrication and weld inspection. The fabricator
will be required to perform quality control and submit weld procedures specifications and certifications
and a quality control plan that addresses the required quality control functions to be performed.
Because of the special requirements of the friction stir welding, it may be necessary to employ
personnel with specialized experience to perform quality assurance for this work.
Rivnut installation and rivnut bolt tightening quality control procedures will need to be developed. Field
welding of main girder supports if permitted will require on‐site involvement by welding inspectors. The
contractor will be required to submit weld procedure specifications and certifications for the field
welding. Quality control procedures for the wearing surface will also need to be developed.
Traffic Control: Because the aluminum orthotropic deck panels will be oriented with the long dimension
perpendicular to the roadway centerline similar to steel open grid panels, there is an opportunity to
replace portions of the deck (i.e. one floorbeam bay at a time in lieu of the entire deck) during short
duration (overnight) closures of the bridge in order to minimize traffic impacts. There are also
opportunities to replace the deck in phases in order to maintain traffic on the bridge while the work is
performed. The modular fabrication of the panels permits the panels to be fabricated in a size (length,
width and thickness) that closely matches that of the existing steel open grid panels to be replaced.
Small openings between the existing steel grid panels and the new aluminum panels due to small
differences in panel dimensions can be temporarily covered with a thin plate. Joints in the panel along
the roadway centerline can permit the panels to be replaced in two halves with traffic maintained on
the opposite half. Details may need to be developed to accommodate bolting of temporary traffic
railing to the aluminum deck panels.
2.2.9 Costs
Construction Costs: The cost of the aluminum orthotropic deck system is anticipated to be significantly
higher than the cost to replace steel open grid roadway flooring (i.e. approximately two times the cost).
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The cost can vary due to a number of factors and depends on the modifications required to fully
implement the aluminum orthotropic deck system. This anticipated work includes a number of items
including:
Removal and disposal of the existing steel open grid and concrete filled deck,
Fabrication and installation of the new aluminum deck panels,
Replacement of the stringers including end connections,
Removal of the main girder spacer bars and installation of new supports including replacement
of some of the top flange rivets with high strength bolts or field welding the supports,
Installation of the wearing surface,
Minor modifications to the counterweight including saw cutting and grouting at the transition to
the aluminum deck,
Adjustment of balance blocks,
Span balance including detailed balance calculations, and instrumentation and recording of the
balanced condition before and after the work,
Adjustment of the live loads shoes in conjunction with the deck alignment,
Adjustment of the span locks in conjunction with the live load shoe adjustments,
Possible modification of the top of the rack frames (bridges with Hopkins frame drive systems
and where the rack frame supports the deck),
Traffic control,
Mobilization work.
Maintenance Costs: The cost to maintain the aluminum orthotropic deck is anticipated to be similar to
that of the steel open grid roadway flooring. Many maintenance activities will be eliminated or
significantly reduced, while other maintenance activities will be added.
Reduced maintenance activities include:
Reduction in the frequency of required cleaning and painting of the bascule leaf steel, as the
solid deck better protects these elements,
Elimination of the need to periodically repair broken steel open grid attachment welds,
Elimination of need to periodically repair cracked secondary and tertiary grid bars,
Elimination of the need to periodically improve skid resistance of steel open grid (e.g.
scarification of top surface),
Reduction in the future replacement of the deck.
Added maintenance activities include:
Periodic repairs or replacement of the wearing surface (e.g. thin epoxy polymer wearing
surface).
Design Cost: The design cost is anticipated to be only slightly more than that for replacement with steel
open grid deck, at least initially, as the design community becomes more comfortable with the design
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and details, develops design skills and work product (plans and calculations) that can be adapted for use
on multiple projects. The available closed‐form design equations facilitate simple design calculations.
Salvage Cost: Aluminum has a relatively high salvage cost due to the high cost of the material. Because
many of the Florida bascule bridges are of a similar configuration, there is an opportunity to relocate the
deck panels from one bridge and use them on another bridge or to store previously used panels for use
to replace damaged panels on an individual basis.
Inspection Cost: The inspection cost may be slightly higher than that required for replacement with steel
open grid deck, at least initially, as the construction community becomes more comfortable with the
quality control requirements for this new type of deck system and the unique materials. The shop
fabrication and welding inspection and field bolting and welding inspection are anticipated to be slightly
more than that for replacement with steel open grid deck.
2.2.10 References
Cousins, T.E., Hezel II, R.F., Gomez, J.P. (2000), Final Report: Classification of Longitudinal Welds in
Aluminum Bridge Deck, Virginia DOT (VTRC Report No. 00‐CR5).
Dobmeier, J.M., Barton, F. W., Gomez, J.P, Massarelli, P.J., McKeel, W.T. (1999), Final Report: Analytical
and Experimental Evaluation of Innovative Aluminum Bridge Deck Panel. Part I: Service Load
Performance. Virginia DOT (VTRC Report No. 99‐R22).
Dobmeier, J.M., Barton, F. W., Gomez, J.P, Massarelli, P.J., McKeel, W.T. (1999), Final Report: Analytical
and Experimental Evaluation of Innovative Aluminum Bridge Deck Panel. Part II: Failure Analysis. Virginia
DOT (VTRC Report No., 99‐R22).
Khaled, T. (2005) An Outsider Looks at Stir Friction Welding. Federal Aviation Administration Report #
ANM‐112N‐05‐06.
Mirmiran, A., Saleem, M.A. (2009), Alternatives to Steel Grid Decks. Draft Final Report, FDOT Contract
Number BC015 RPWO 22.
Misch, P.J., Barton, F.W., Gomez, J.P., Masserelli, P.J., McKeel, W.T. (1999), Final Report: Experimental
and Analytical Evaluation of and Aluminum Deck Bridge. Virginia DOT (VTRC Report No. 00‐R10).
Prince, R.T. (1997) Evaluation of Field Tests Performed on an Aluminum Deck Bridge. Master of Science
Thesis, Virginia Polytechnic Institute and State University.
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2.3. FIBERGLASS REINFORCED POLYMER (FRP) COMPOSITE DECK
2.3.1 Description
Fiberglass reinforced plastic (FRP) is a composite material that has a number of characteristics that
makes it a good alternative to replace steel open grid deck on bascule bridges. FRP composites can be
designed to provide a wide range of mechanical properties including tensile, flexural, impact and
compressive strengths. FRP composites are generally lightweight (i.e. approximately 20% of steel) with
high strength‐to‐weight ratio and are generally resistant to creep and fatigue. FRP composites are
versatile and can be fabricated in many different configurations, customized specifically for a given
application (e.g. bridge decks), designed and fabricated such that the strength is oriented to meet
specific configuration and loading demands, made into larger more complex structural components and
systems that simplifies connections and minimizes the number of components that must be handled.
The relatively low modulus of elasticity of FRP composites make them relatively flexible compared to
other bridge deck materials and thus deflections generally control the design of FRP bridge decks. FRP
composite materials are susceptible to degradation from ultraviolet light and chemicals; however, the
materials can be formulated with additives to improve the resistance to these effects.
Material: FRP generally consists of a combination of:
Polymer (plastic) matrix (e.g. thermoplastic or thermoset resin) such as polyester, isopolyester,
vinyl ester, epoxy, or phenolic,
Reinforcing agent (e.g. as fiberglass, carbon fiber, aramid or other reinforcing material) such that
there is a sufficient aspect ratio (length to thickness) to provide a discernible reinforcing
function in one or more directions.
May also contain fillers, additives, core materials that modify and enhance the final product.
The constituent elements in a composite retain their identities (they do not dissolve or merge
completely into each other) while acting in concert to yield the desired properties.
Various FRP composite bridge deck products have been developed over the last 15 years. Thickness of
the various deck products have ranged from 4 to 9 inches depending on the intended application and
the thickness of the existing bridge deck to be replaced. Decks are typically designed to be supported on
and span transversely across longitudinally spanning girders or stringers similar to other conventional
decks. The FRP composite decks are typically modular with panels joined together in the field to create
a seamless final installation. The length of the panels are typically equal to the full width of the bridge
and the width of individual panels are typically 8 to 10 feet wide for fabrication, shipping and handling
purposes. The majority of FRP composite deck systems consist of pultruded shapes that are adhesively
or mechanically bonded together in the field, and mechanically fastened to the supporting structural
framing. Nearly all FRP composite decks that have been developed are multi‐cell hollow sections with
top and bottom faceplates and a series of web members that connect the top and bottom face plates.
The configuration of the cross section and details including splices between panels and connection to
the supporting structure has varied significantly among different deck products.
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2.3.2 Product Development and Corporate Information
Since 1996, there have been a number of different FRP composite deck systems that have been
developed, tested, and put into service throughout the United States. More than 80 vehicular bridges in
the United States have been constructed or rehabilitated using FRP composite decks. FRP composite
bridge decks technology continues to evolve with ongoing research and product development and
enhancement. Installations to date have yielded mixed durability and performance results.
Fabrication of FRP composites typically uses one of three current manufacturing techniques:
Pultrusion: Pultrusion is a manufacturing process for producing continuous lengths of reinforced
polymer structural shapes with constant cross sections. Raw materials consist of a liquid resin mixture
and flexible textile reinforcing fibers. The process involves pulling the raw materials through a heated
steel‐forming die using a continuous pulling device. The continuous reinforcement materials are
saturated with the resin mixture in a resin bath and pulled through the die. Heat from the die initiates
the gelation (or hardening) of the resin. A rigid, cured profile is formed that corresponds to the shape of
the die.
The advantage of pultrusion is that the manufacturing produces a well‐controlled and consistent
dimensional profile. Pultrusion is the most automated process, requiring little hands‐on labor. Internal
die segments allow open or wrap‐around shapes to be designed and details such as hollow tubes and
trapezoids to be produced. The disadvantage is that pultrusion produces long, narrow profiles, so deck
designs employing pultrusion must consider how to combine pultruded elements to create the
necessary width. Pultrusion is by far the most common method used in fabricating FRP composites for
bridge deck applications.
Vacuum‐Assisted Resin‐Transfer Molding (VARTM): VARTM employs a soft bag over the part to seal the
mold so that a vacuum can be drawn under the bag. Once vacuum is achieved, the part is pressed onto
the hard tool by atmospheric pressure. Resin ports on feed tubes are then opened to permit resin to
flow into the mold and infiltrate the dry fabric reinforcement.
The advantage of VARTM is rapid infusion of large parts when the procedure works. Infusion of large
sections can be accomplished in minutes. Because the fiber reinforcement is compressed and locked in
place by atmospheric pressure on the soft bag side, high fiber volume can be achieved. Good
dimensional tolerance also is achieved because excess resin can just flow out of the vacuum ports.
Because the resin flows indiscriminately under vacuum, the VARTM process requires volumetrically
nearly solid sections in order to avoid forming resin‐rich areas or resin pools in cavities. Also, any
nonstructural materials such as foam core must be able to sustain the atmospheric pressure without
crushing.
Hand Lay‐up or Open Molding: The hand lay‐up process is the most fundamental method of
manufacturing still widely used in all industries. Fiber reinforcement is placed in position on the mold or
plate and then saturated with resin. A crew then uses specialized rollers and paddles to work the resin
into the fabric, fully wetting the layer. After determining that the layer is fully wetted, the crew repeats
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the process on succeeding layers until the lamination is complete. The component is then left to cure
thoroughly, which takes from a few hours to overnight.
The advantage of hand lay‐up is its low capital equipment costs and the low‐to‐moderate labor skill
required. These factors usually make it the least expensive method for one‐of‐a‐kind or limited
production work. For complex parts, this may be the only feasible method. The disadvantage of this
process is the variability in procedure and material properties due to the manual labor involved.
In addition to the above manufacturing processes, additional secondary fabrication and assembly is
usually required before panels are shipped including:
Bonding components together to make larger components and assemblies using epoxy
adhesives,
Pre‐drilling holes for component and panel connections and splices for use in the field,
Material repairs,
Application of gel coat,
Surface preparation of top faceplate to accept the wearing surface.
FRP composite deck components are then shipped to the site, installed on the bridge structural framing,
spliced together, and secured to the structural framing.
Splicing of components and panels has been performed using a number of details including both epoxy
adhesive bonded, bolted, or screwed lap joints. Panels have been connected and secured to the bridge
structural framing using a number of different attachments including welded headed studs attached to
the steel structure and grouted keyways within the panels or through bolted connections.
2.3.3 Recent Bridge Installations
Although there are numerous available FRP composite deck products, because the support conditions,
steel framing configurations, and corresponding stresses and structural deformations on bascule bridges
are different than those on typical parallel, multi‐girder fixed bridges, only FRP deck systems that have
been installed on bascule bridges are investigated and evaluated in this study. Two (2) FRP composite
bridge deck systems have been used on bascule bridges in the United States:
DuraSpan: The DuraSpan FRP composite deck system was manufactured by Martin Marietta
Composites. The deck system consists of a series of 5‐inch or 8‐inch deep, rectangular, multi‐cell
pultruded tubular deck planks spliced together in the field using epoxy adhesive bonded lap joints to
make a continuous closed deck system. The deck planks are connected to the supporting structural
framing using mechanical fasteners (e.g. welded headed studs with grouted cavity within the deck).
The deck system was installed on three bascule bridges by Oregon Department of Transportation from
2001 through 2005, one bascule bridge by Multnomah County, Oregon in 2006, and one vertical‐lift
bridge at the Port of Long Beach, California in 2003. The deck system has also been installed on several
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fixed bridges. The in‐service product has developed a number of maintenance and durability issues and
is no longer produced and supported by Martin Marietta Composites.
DuraSpan FRP Composite Deck Panel
ZellComp: The ZellComp FRP composite bridge deck system was initially developed in 2002 and put in to
production in 2005. ZellComp has 5‐, 7‐ and 9‐inch deep versions of the deck system. The deck consists
of individual 32‐inch wide lower pultruded sections panels each with four T‐sections that resemble small
wide‐flanges and made integral with a bottom plate, and a separate top faceplate that is mechanically
fastened to the bottom panel. The pultruded FRP composite parts are mechanically connected together
in the field (in lieu of bonded epoxy adhesive joints) to
create a continuous closed, multi‐cell, tubular deck system.
The lower pultrusion is connected to the supporting steel
framing using mechanical fasteners (e.g. through bolting of
the bottom plate or welded headed studs with grouted
cavity within the deck). The open shape of the lower
pultrusion facilitates this connection. The upper faceplate is
connected to the lower pultrusion after the lower
pultrusion is connected to the structural framing. The
faceplate is secured to the top flanges of the pultruded
wide‐flange components using mechanical fasteners. Self‐
tapping screws were initially used to make the blind‐
connection from the top. Following some performance issues with this connection, improvements to
this connection have been proposed utilizing rivnuts (internally threaded rivets) attached to the top
flange of the wide‐flanges.
The 5‐inch deep version of the deck has been installed on one bascule span in 2011 and is in the process
of being installed on a second bascule span in 2012, by Multnomah County, Oregon. The deck system
has also been installed on several fixed bridges throughout the United States.
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Lewis and Clark Bridge: Lewis and Clark Bridge, rehabilitated in 2001, over Lewis and Clark River on US
101 in Clatsop County, near Astoria, OR was one of two bascule bridges in the United States to first
receive an FRP deck.
Bridge is owned and maintained by Oregon
Department of Transportation,
Originally built in 1924,
112‐foot Single‐leaf Bascule Span with 20‐foot
deck width with stringers at 2’‐9” on center,
Steel open grid deck was replaced with DuraSpan
FRP bridge deck system (manufactured by Martin
Marietta composites). The deck, composed
primarily of glass fibers and polyester resin, was
nominally 5 inches thick and weighed approx.
15 psf,
77,000 lbs. of ballast required for each
counterweight,
2‐inch thick epoxy concrete wearing surface
exhibited cracking within 1 year and is in very
poor condition after 9 years,
FRP composite deck and connections are sound
after 9 years,
A field visit of the bridge in December 2011 by the
research team revealed that the FRP deck is in
poor condition with signs of the typical cracking
at the joints and adjacent failure of the wearing
surface as well as random delamination and cracking throughout,
Bridge carries an average of 3,300 vehicles per day and is posted for a load limit of 40 Tons.
Old Youngs Bay Bridge: Old Youngs Bay Bridge, rehabilitated in 2002, over Youngs Bay on US 101 in
Clatsop County, near Astoria, OR was one of two bascule bridges in the United States to first receive an
FRP deck.
Bridge is owned and maintained by Oregon
Department of Transportation,
Originally built in 1921,
166‐foot Double‐leaf Bascule Span with 20‐foot
deck width with 5’‐4” stringer spacing,
Bridge carries an average of 5,600 vehicles per
day and is posted for a load limit of 40 Tons,
Steel open grid deck was replaced with DuraSpan
FRP bridge deck system (manufactured by Martin
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Marietta composites). The deck, composed primarily of glass fibers and polyester resin, was
nominally 5 inches thick and weighed approximately 15 psf,
30,000 lbs. of ballast required for each counterweight,
½‐inch epoxy concrete wearing surface exhibited
cracking in less than 1 year and severe cracking
after 4 years,
FRP composite deck and connections failed after
5 years including punch through in a few locations
and deck‐stringer connections breaking apart,
FRP composite deck was replaced with a steel
open grid deck in 2010 following poor
performance and premature failure of the FRP
deck.
Siuslaw River Bridge: Siuslaw River Bridge, rehabilitated in 2005, over Siuslaw River on US 101 in
Florence, OR is an historic bridge that received an FRP deck.
Bridge is owned and maintained by Oregon
Department of Transportation,
Originally built in 1936,
149‐foot Single‐leaf Bascule Span with 27‐foot
deck width,
Bridge carries an average of 20,000 vehicles per
day,
Steel open grid deck was replaced with DuraSpan
FRP bridge deck system (manufactured by Martin
Marietta composites). The deck, composed
primarily of glass fibers and polyester resin, was
nominally 5 inches thick and weighed approx.
15 psf.
Wearing surface (URE‐FAST PF‐60 consisting of
two‐component urethane, sprayed into pre‐
placed crushed rock and topped with coarse sand
to create a semi‐rigid polymer concrete) is in
good condition with minor to moderate wear
after 6 years.
Connection details show minor and localized degradation
Broadway Bridge: Broadway Bridge, rehabilitated in 2004
over the Willamette River, Portland, Oregon is the largest
bascule bridge in the world with an FRP deck.
Bridge is owned and maintained by Multnomah
County,
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Originally built in 1913, the historic bridge has served Portland’s marine (river) and vehicular
traffic quite well for more than 90 years,
278‐foot Double‐leaf Rall Type Bascule Span with a
46‐foot deck width, is the seventh longest bascule
bridge in the world,
Bridge carries an average of 29,400 vehicles per
day,
Steel open grid deck was replaced with DuraSpan
FRP bridge deck system (manufactured by Martin
Marietta composites). The deck, composed
primarily of glass fibers and polyester resin, was
nominally 5 inches thick and weighed approx.
15 psf,
A portion of the DuraSpan FRP deck was removed and replaced with a ZellComp FRP deck in
2011 to accommodate a new street car.
A field visit of the bridge and meeting with the owner in December 2011 by the research team
revealed the following:
o The First FRP deck has experienced some surface cracking and debonding of the friction
course. Cracking occurred at the grouted connections. The owner believes this is due to
the stiffening effect of the grout compared with the otherwise flexible FRP. Some of the
surface debonding is random – at locations other than the joints.
o The new ZellComp FRP replacement deck has developed cracks at the transverse joints
between deck plates soon after being subjected to traffic. These joints have been saw
cut and filled with joint sealant. To date, the friction course overlay (3/8” aggregate
broadcast onto epoxy) has remained securely bonded.
o The owner reported that ZellComp initially applied a coating with a non‐slip surface on
the FRP top plate to receive the wearing surface, but the wearing surface debonded
under traffic. In testing various methods of surface preparation, the owner determined
that a shot blasted surface improved the bond of an aggregate broadcast on epoxy.
o The owner has decided to use rivnuts to secure the top plate to the lower pultrusion in
the field and has demonstrated that the screws can be replaced if needed.
Morrison Bridge: Morrison Bridge, rehabilitated in 2012, over Willamette River in Portland, Oregon is
the most recent bascule bridge to receive an FRP deck and will have the highest volume of traffic for a
bridge with FRP deck.
Bridge is owned and maintained by Multnomah County,
Originally built in 1958,
340‐foot Double‐leaf Bascule Span with a 78‐foot deck width,
Bridge carries an average of 53,800 vehicles per day,
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Steel open grid deck is in the process of being replaced with a ZellComp FRP bridge deck system. The
deck, composed primarily of glass fibers and polyester resin, has a nominal thickness of 5 inches and
weighs approximately 21 psf. ZellComp has added a glass mat across the joints in the top plates,
bonded with resin in an attempt to prevent cracking of the friction course. The deck is bolted to the
stringers.
Other Bridge Products: There are a number of other FRP composite bridge deck products that have
been developed and others currently in development, but none of these have been installed on
vehicular bascule bridges in the United States (e.g. Strongwell, Bridge Composites, FiberSpan, et al).
2.3.4 Design and Analysis
Design Considerations: Although there has been significant research and development of FRP
composite deck system over the last 15 years, industry standard design and construction specifications,
and guidelines are not available. As such, the use of FRP composite bridge decks is generally still
considered experimental. Most of the current FRP composite deck products are proprietary, designed
using product or project specific research, and manufactured using proprietary material formulations
and/or fabrication methods. Most installations by bridge owners have relied upon manufacturer
research, technical data, guidelines and recommendations.
The lack of industry standard design and construction specifications and guidelines is largely due to the
proprietary nature and wide variety of FRP composite deck products. This is expected given that the FRP
composite technology permits products (e.g. bridge decks) to be readily customized including fibers,
fiber architecture, and resins to suit a specific application. The nature of manufacturers to protect the
intellectual property of the proprietary product research and development is not conducive to
development of standardized design and construction specifications and guidelines. As such, there is
limited interchangeability between various FRP composite deck products.
The significant variety of proprietary FRP composite deck products includes significant variations in:
Cross‐sectional geometry,
Design and performance criteria,
Materials including the resins, reinforcing, reinforcing architecture,
Manufacturing methods,
Critical details including deck structure, connections between components and subsystems, and
connections to the supporting bridge structure,
Type, quantity and quality of research, analysis, testing, evaluation and peer review used to
validate the deck product.
The use of performance‐related specifications instead of prescriptive specifications has been
problematic. Performance‐related specifications are not conducive for products that require long‐term
(greater than five years) maintenance performance as it is not practical to enforce performance
requirements long into the future. Without prescriptive specifications, product details can be easily
changed without validation from through testing and evaluation.
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Relevant Research: Over the last 15 years, there has been very limited interaction and no continuity or
common goals between various research projects. Aside from scholarly journal articles, which typically
appear long after project completion, and conference presentations, in which details are sketchy, the
sharing of findings is virtually nonexistent. The ineffectual end results of these fragmented efforts over
the last 15 years support these conclusions.
Most research has demonstrated that FRP composite decks have significant strength and can easily be
designed and developed to resist HL‐93 design live loading at the Strength Limit State in the AASHTO
LRFD Bridge Design Specifications. However, because of the low modulus of elasticity of FRP composite
materials and the flexibility of FRP composite decks, other aspects of the deck design (e.g. deflection,
fatigue of connection and panel splice details, wearing surface performance) usually are more important
in the deck product development. Strength and stiffness of the FRP composite depends on the type,
quantity and orientation of the fiber reinforcing, and resin matrix used to form composite material.
Design Approach: Currently, there is no simplified structural analysis method (e.g. simplified closed‐
form equations) endorsed by AASHTO that are available to accurately compute the live load wheel
distribution for FRP composite decks. However, research performed in 2007 by Virginia Polytechnic
Institute and State University, that included an extensive parametric study using finite element analysis
and validated by laboratory testing, yielded a proposed an equivalent strip equation:
W = 0.0046S2 ‐ 0.47S + 28, where, S = Girder Spacing (inches)
It is observed that the deck relative deflections from strip method generally show good agreement with
the lab measurements for the cases when lab measurements are available. The research is based on a
single FRP composite bridge deck type, Strongwell FRP Deck, and thus it is not clear whether the
equation is applicable to other FRP composite decks. In the absence of similar research for other FRP
composite decks, it gives a simplified general approach that can be used. The research concluded that
the strip method specified in AASHTO LRFD Bridge Design Specifications for analysis of concrete, steel
grid and timber decks can also be applied to FRP composite decks in conjunction with the proposed strip
width equation.
AASHTO LRFD Bridge Design Specifications do not provide equations to determine the live load
distribution factor for steel beams when the deck consists of an FRP composite material. The same
research above by Virginia Polytechnic Institute and State University included a parametric study to
estimate live load distribution factor for this case. Both finite element analysis and laboratory testing
demonstrated that the live load distribution factor equation for glued laminated timber decks on steel
stringers provide a good estimate of load distribution factor for FRP composite deck on steel girders.
This is likely because FRP composite decks generally have similar stiffness to laminated timber decks.
The lever rule approach can also be used to conservatively estimate the live load distribution factor for
FRP composite deck on steel girders. This research was performed with the conservative assumption
that the FRP deck is non‐composite with the steel girders.
The ZellComp 5‐inch deep FRP composite deck was evaluated using the closed‐from equation above for
the stringer spacing found on typical Florida bascule bridges. The deck met Strength I Limit State, but
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calculated Service I Limit State deflections were 0.10” (L/467), which is greater than the L/800 deflection
limits. Because testing of this deck system identified loosening of screws and loss of composite action
between upper facesheet and the lower pultrusion, section properties conservatively consider the lower
pultrusion only. Because of the issues with the facesheet fasteners, it is recommended that alternative
fasteners (e.g. Rivnuts) be considered, evaluated and tested. Successful strength and fatigue testing of
alternative fasteners may permit the upper faceplate to be considered as composite with the lower
pultrusion with reduced calculated deflections.
There are several factors that must be considered in making a decision regarding the design of the deck
for deflections:
Although AASHTO LRFD Bridge Design Specifications do not specifically address the deflection
limits of FRP composite decks, mandatory L/800 deflection limits for these decks have been
endorsed by many researchers, bridge owners, and FHWA similar to that of steel grid and other
lightweight metal decks. However, other researchers and bridge owners have endorsed less
restrictive L/500 deflection limits.
The selection of a deflection limit yields significant differences in the final FRP composite deck
design and makes a difference whether the solution is viable or not viable. In order to meet
L/800 deflection limits, a ZellComp deck with a depth greater than 5 inches is required using
stringer spacing on typical Florida bascule bridges, which is difficult to accommodate due to the
significant modifications to the bridge required to raise the roadway profile grade.
Alternatively, additional stringers can be added and/or the stringers re‐spaced; however, this
adds weight to the bascule leaf.
The effect of deflections on driver comfort is not likely to be a concern for the anticipated deck
span lengths. Live load deck deflections are anticipated to be small (i.e. less than ¼”) and are
anticipated to remain constant over the length of the bascule span (i.e. deflections will not vary
over the length of the bascule span and cause vertical accelerations that affect driver comfort).
For the typical bascule span framing configuration, maximum deflections will occur directly
under the wheel and deck stiffness will generally remain uniform over the length of the bascule
span where the deck is supported only by the stringers and not directly supported at the
floorbeams. Research indicates that vertical acceleration limits is a more appropriate means of
addressing driver comfort than arbitrary deflection limits.
Various studies regarding dynamic amplification of live loads indicates that dynamic
amplification values increase with decreasing deck stiffness. As such, dynamic load allowances
specified by AASHTO may underestimate actual values on flexible decks. A conservative
estimate of the dynamic load allowance is recommended for the FRP composite deck design if a
more flexible deflection limit than L/800 is used.
Excessive deflections may result in durability concerns for the wearing surface. Wearing surface
durability is a well‐documented concern on bridges with orthotropic decks with flexible deck
plates. There are no specific studies that have tested the durability of thin epoxy polymer
wearing surfaces on flexible FRP composite decks. However, case studies of existing FRP decks
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with thin epoxy polymer overlays indicated that premature failure of the wearing surface is a
wide spread problem.
In order to reduce the weight of the FRP composite deck on a bascule span, lightweight thin
wearing surfaces are required. Thin wearing surfaces do not have the ability to distribute wheel
contact pressures to a larger surface area like thicker asphalt wearing surfaces used on some
FRP composite deck installations. As such, wheel patch loads are likely more concentrated.
Laboratory testing of FRP composite decks has typically taken a conservative approach that
neglects the load distribution benefit of the asphalt wearing surfaces.
The modulus of elasticity of the resins used in FRP composite material reduces with increased
temperatures and temperatures in Florida are generally higher than those in northern climates.
Research demonstrated a loss in stiffness of nearly 20% to 25% over a temperature range from
70 to 130°F. As such, it is recommended that conservative physical properties corresponding to
maximum anticipated in‐service temperatures be used in the design of the deck for deflections.
Exposure of FRP composites to ultraviolet light has shown to cause degradation causing micro‐
cracking of the composite resins that reduce the stiffness of the deck and increases deflections.
The following additional design considerations are recommended by FHWA in the absence of provisions
in AASHTO LRFD Bridge Design Specifications.
To avoid long term creep, predicted strains under design load should be less than 20% of the
FRP composite material minimum guaranteed ultimate strength based on coupon testing.
An environmental durability factor of 0.65 is recommended to the material properties to
account for degradation of properties over time.
In cases where the deck is expected to fail in a manner other than tension of the laminate, a
factor of safety of five should be applied.
Because of the material's typical low modulus of elasticity, most designs will be driven by
deflection limitations and not strength requirements. Although the criterion for deflection is
somewhat arbitrary, it is typically be kept at 1/800 of the supporting span length.
2.3.5 Functionality and Safety
Load Capacity: An FRP composite deck designed to governing stress limits with sufficient reserve
capacity to address anticipated degradation will have corresponding load carrying capacity in excess of
that required to support AASHTO LRFD HL‐93 Live Loads. The unit weight of the proposed FRP
composite deck will be close to that of the existing steel open grid deck, and thus the weight of the deck
is not anticipated to significantly reduce the capacity of bascule span members.
Rideability: The FRP composite deck and the corresponding applied wearing surface will provide a
smooth, continuous riding surface with a surface roughness comparable to asphalt or concrete
pavement.
Due to the relatively low modulus of elasticity of FRP composites, the decks exhibit relatively low
flexural stiffness and corresponding greater deflections and vibrations that are a significant design issue.
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Vibration characteristics of FRP composite decks have been shown to be significantly different from
those of conventional reinforced concrete bridge decks, necessitating a further evaluation of deflection
criteria for these decks. For reference, research has demonstrated that FRP composite decks generally
deflect 50 to 60% more than typical concrete decks for the same deck span. Although mandatory L/800
deflection limits for these decks have generally been applied, similar to that of steel grid and other
lightweight metal decks, some researchers have surmised that better economy could be achieved if this
deflection limit were liberalized. This has lead researchers to suggest a number of alternative
serviceability criteria including new proposed empirical formulations for calculating maximum live load
acceleration response, as a function of the first bending modal frequency of the bridge, and
corresponding alternative serviceability criteria that limits vertical acceleration to that consistent with
human tolerance to vibrations.
Skid Resistance: Skid resistance from the applied wearing surface will be similar to that of asphalt
pavement. See Section 3 Wearing Surface Evaluation.
Noise: The solid surface of the FRP composite deck is anticipated to reduce noise generated by tires in
contact with the deck relative to steel open grid deck. However, the hollow cells of the deck may still
generate some resonance due to vibration of the deck thin web members.
Bicycle Safety: The FRP composite deck provides a solid riding surface for the roadway and shoulders
with small longitudinal open joints (less than ½” wide) located immediately adjacent to the curbs or
barriers, which will greatly improve bicycle safety. Transverse deck joints between the two bascule
leaves and between the bascule span and bascule pier will range from ¾” to 1½” in width, but should
not be a concern for bicyclists.
2.3.6 Durability and Service Life
Service Life: The primary concerns with FRP composite bridge decks are durability and service life. An
investigation performed in 2006 reviewed the performance of the FRP composite decks of 83 bridges
constructed from 1999 to 2001. Although this study did not concentrate on FRP composite decks found
on bascule bridges, the issues described are symptomatic of the issues found on bascule bridges.
Although the average age of these decks was less than 5 years at the time, the survey indicated that the
bridges exhibited a number of concerns and problems, including issues with:
Failure of the deck at joints between deck panels with corresponding reflective cracking in the
wearing surface and water leakage through the joints to the steel framing below,
Delamination and debonding of thin wearing surfaces,
Non‐uniform support of the deck at the haunch supports with corresponding panel movement
under traffic,
Failure of the traffic railing curbs and parapets,
Failure at approach joints,
Failure of deck connectors, which ranged from bolted clamp‐type connectors to welded headed
studs in grouted cavities in the deck,
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Delamination of the FRP composite materials and corresponding moisture ingress that makes
the material susceptible to freeze‐thaw.
A series of pictures below illustrate typical deficiencies.
Reflective cracking and oozed material at FRP deck‐to‐deck joints
Debonding at Joint and below Wear Misalignment of Deck‐to‐Deck Joint
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Leakage through Deck‐to‐Deck Joint FRP Deck and Connection Studs Separation
Clip Type Connection Separation Crack in Haunch
Delamination of Wearing Surface Wearing Durface Debonding
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Buckling of Wearing Surface Typical Steel Railing Connection
Factory Joint on Pultruded Sandwich Deck Section of Deck with a 3‐ft Diameter Bubble
Water found within core of deck after drilling Tearing of core and faceplate buckling
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Faceplate crippling FRP Delamination (ZellComp)
Lip Separation (ZellComp Deck) Web Buckling (ZellComp Deck)
Creep Resistance: The addition of the reinforcement to the polymer matrix increases the creep
resistance (i.e. resistance to permanent deformations from sustained loads). Creep is generally not a
concern for FRP composite bridge decks as the deck is not subject to large permanent loads.
Environmental Exposure: Although FRP composite materials are non‐corrosive materials and deicing
chemicals and saltwater will not corrode the material, exposure to these can degrade the strength and
stiffness of the FRP composite material. Research demonstrated degradation of the FRP composite
material from environmental exposure (30% decrease in modulus of elasticity and corresponding panel
stiffness when exposed to a calcium chloride solution; 35% decrease in tensile strength when exposed to
a sodium hydroxide solution). Degradation is believed to be accelerated with higher moisture and
elevated temperatures.
In addition, FRP composite materials were found to degrade from weathering effects, particularly by
ultraviolet (UV) light. Ultraviolet photons from the natural solar radiation cause photo‐oxidative
reactions that can alter the molecular chain of polymers and produce micro cracking in the polymer.
Both laboratory testing and observations and testing of in‐service FRP composite materials identified
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surface micro‐cracking and chemical degradation of the epoxy and corresponding reduction in tensile
strength of FRP composite materials. Laboratory testing that included exposure of fiberglass and carbon
fiber reinforcing samples to UV radiation demonstrated 10% reduction in tensile strength. FRP
composite materials exposed to sunshine for a period of 42 months experienced a 40% reduction in
tensile strength.
FRP composite materials that will be subject to these conditions are normally fabricated with a surface
layer containing a pigmented gel coat or UV inhibitor included as an additive to the composite matrix.
Both methods provide protection to the underlying material by screening out UV rays and minimizing
water absorption along the fiber‐resin interface. The thin epoxy polymer wearing surface can also act to
protect the upper faceplate from exposure. The durability of FRP composite materials in the alkaline
environment and from exposure to UV light is strongly dependent on resin types and the manufacturing
processes. Degradation has shown to occur if the fiber reinforcing is not properly coated and shielded
by the resin matrix. Cutting and drilling of FRP composite panels can expose the fiber reinforcing. The
protective benefit of the wearing surface is removed if the wearing surface is breached.
Freeze‐thaw Resistance: FRP composites have low water absorption and thus are generally considered
resistant to destructive expansion of freezing water. However, research has shown that freeze‐thaw
cycles in cold region environments can result in degradation of the FRP composite materials. Micro‐
cracks and voids in the polymer matrix can develop during extreme temperature changes due to
differences in the coefficients of thermal expansion of fibers and resin. These cracks and voids can retain
moisture that can freeze. Research conducted cyclic tests on FRP sandwich deck panels at very cold
temperatures (as low as ‐67°F). At these very low temperatures, the stiffness of the specimen decreased
10 to 20% compared to that at room temperature and the degradation in stiffness could not be
recovered. Strength reduction ranged from 10% to 30%. Freeze thaw is not anticipated to be a
significant concern on most Florida bascule bridges due to the generally mild temperatures found in
Florida.
Chemical Resistance: FRP composites can be formulated to provide long‐term resistance to nearly every
chemical and temperature environment including the destructive effects of de‐icing salts and saltwater.
However, these considerations have not necessarily been considered in the development of most of the
FRP composite deck products. As such, the chemical resistance of these products is unclear.
Fatigue Resistance: Fatigue testing of the FRP composite deck material for cycles of 2 million to 10
million cycles has generally demonstrated good fatigue resistance. However, instances of delamination
of the FRP composite material have been identified. Research also indicates that a combination of
environmental exposure (e.g. UV light and saltwater) and repeated application of load can result in
degradation of FRP composite physical properties including modulus of elasticity and panel stiffness.
Researchers have suggested that this effect should be accounted for in the design, similar to sacrificial
loss in thickness of steel members or prestress losses. Although much research has been done on the
mechanical properties of FRP composites, the overall long‐term durability of the material under severe
environmental conditions has not been systematically evaluated.
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The ZellComp FRP composite deck was specifically tested to investigate the self‐tapping screw
connection of the upper faceplate to the lower pultrusion. This research investigated the fatigue and
failure strength of the deck and connection under cyclic loading. The testing identified significant
loosening of screws and eventual fracturing of the fasteners after only 600,000 cycles that increased as
the testing continued and movement of the upper faceplate that can result in corresponding cracking,
delaminating and spalling of the wearing surface. It is recommended that alternative fasteners (e.g.
Rivnuts) be considered, evaluated and tested.
Fire Resistance: Composites can be designed to meet fire regulations by the use of special resins and
additives. Properly designed and formulated composites can offer fire performance approaching that of
most metals. However, most FRP composite materials for bridge deck applications have not been
developed with fire as a consideration and thus it is unclear how these materials will perform in the
event of a fire.
Performance of FRP composite materials in a fire includes a number of considerations. FRP composites
can burn under certain conditions. Extreme heat can degrade the FRP composite material, which shows
lower heat resistance than conventional construction materials. Research of fire resistance of FRP
composite structural members, which explored a number of fire scenarios with different locations above
and below the bridge, predicted failure of the FRP composite materials in less than 8 minutes for a
burning truck on the deck. Structural collapse was found for combined thermal and mechanical loading.
As such, immediate evacuation of a bridge with an FRP deck subjected to fire is required. Other
research demonstrated that even less extreme temperatures can cause problems for FRP decks
including delamination between the resin and glass and thermal deformations and uplifts depending on
the panel details and thermal gradients.
Relatively closely spaced stringers on a bascule span are likely to retain vehicles after the deck fails.
However, fire on FRP composite deck can potentially make emergency response more problematic.
Rescue efforts are likely to be hampered with the early loss in strength of the FRP composite deck.
Impact Resistance: FRP composite materials have generally shown to have some energy absorbing
properties to resist collision. Although the FRP composite material glass reinforcing and resin matrix can
be developed specifically to improve impact resistance, this has generally not been a primary
consideration in the development of most FRP composite bridge decks. It is unclear how the deck upper
faceplate and hollows tubular sections will perform under a vehicular collision.
Thermal Expansion: Response to thermal change is slightly different for FRP composite material than for
concrete and steel and requires special consideration when an FRP deck is used on a concrete or steel
superstructure. FRP composite material can heat up rapidly when exposed to direct sunlight. A dark
wearing surface exacerbates the phenomenon. Experience has shown that a thermal gradient will occur
between the top and bottom of an FRP deck when surface temperatures change fast but are not able to
be conducted through the FRP immediately. This problem is especially likely to occur in early spring or
late fall. The design should assume a temperature difference between the top and bottom of the deck
and account for any subsequent internal thermal stresses. Since this temperature gradient can lead to
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an arching action as the top surface expands faster than the bottom, it may also affect the selection of
bearing and anchorage details. It is important to note that thermal stresses may be as large as stresses
resulting from live loads.
The difference in coefficients of thermal expansion between FRP composite and steel framing and the
restraining effects from bolting the deck to the steel framing and the stiffness of the steel framing must
be considered in detailing the deck. In addition, as the FRP composite deck will have more direct
exposure (i.e. the deck will be directly exposed to the sun, while the steel framing will be shaded by the
deck) the temperature of the FRP composite deck is anticipated to be significantly different than the
temperature of the steel. Differential movement between the two materials is anticipated to be
measurable. Because of the magnitude of these differential movements, details for attaching the deck
will need to accommodate the movement and prevent restraint that would develop large forces in the
deck and steel framing members. More accurate assessment of the differential temperature will need to
be determined during design.
The difference in thermal expansion can be addressed as follows:
Deck panels will extend transversely the full width of the roadway, from curb to curb, for a
typical two lane Florida Bascule bridge.
Deck panels will extend transversely half the width of the roadway, with an expansion joint in
the middle of the roadway, beneath the median for a typical four lane Florida bascule bridge.
The panels will be spliced such that they are continuous in the longitudinal direction, except for
one or two intermediate expansion joints between the panels.
Oversized holes in the steel members will be used to accommodate thermal expansion with
standard sized holes used at the center of thermal movement to secure and maintain the
alignment of the panels as the movement occurs and as the bridge raises and lowers.
2.3.7 Florida Bascule Bridge Specific Solution
Deck Solution: Although there have been a number of
FRP composite decks that have been developed over the
last 15 years, the ZellComp 5‐inch deep FRP composite
deck is a good candidate for use on a typical Florida
bascule bridge with a depth that can be easily
accommodated with minimal modifications and that has
an overall unit weight similar to that of the typical steel
open grid deck to be replaced. The 5‐inch deep
ZellComp FRP composite deck has already been installed
on one bascule span and is in the process of being
installed on another bascule span.
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The deck consists of individual 32‐inch wide lower pultruded panels each with four T‐sections that
resemble small wide‐flanges and made integral with a bottom plate, and a separate pultruded top
faceplate that is mechanically fastened to the lower panel. The top and bottom plates are ½‐inch thick
and the wide‐flanges are spaced 8 inches on center.
The unit weight of the 5‐inch deep ZellComp deck is 16 psf, excluding connections and wearing surface.
With these other items the total unit weight is approximately 21 psf which includes a bolted connection
(in lieu of a grouted connection) and 3.5 psf of wearing surface.
Panel Splices: The pultruded FRP composite parts are mechanically connected together in the field (in
lieu of bonded epoxy adhesive joints) with stainless steel fasteners to create a continuous closed, multi‐
cell, tubular deck system. The lower pultruded panels are placed side‐by‐side, with a small overlap of a
dapped portion of the bottom plate. There are some concerns that the extensive drilling required for the
numerous small fasteners may introduce stress risers that are conducive to crack formation and that
provide passage for moisture and salts to access the interior of the laminates. The use of epoxy
adhesives to connect the panel components has not been tested with the ZellComp deck.
Deck Connection: The lower pultruded panel is connected to the supporting steel framing by through
bolting to the stringer and floorbeam top flanges and new main girder supports (in lieu of welded
headed studs with grouted cavity within the deck, which adds too much weight). The open shape of the
lower pultrusion facilitates this connection. Neoprene pads are used between the steel framing and the
FRP composite panels to provide a more uniform bearing surface. The upper faceplate is connected to
the lower pultrusion after the lower pultrusion is connected to the structural framing. The faceplate will
be secured to the top flanges of the pultruded wide‐flange components using Rivnuts (internally
threaded rivets) attached to the top flange of the wide‐flanges in lieu of the previously used self‐tapping
screws that had performance concerns.
Structural Modifications: The following modifications to the bridge are required to implement the 5‐inch
deep ZellComp FRP composite deck:
Existing stringers supporting existing steel open grid deck can be reused and remain as currently
configured. However, replacement of the stringers would:
o Facilitate shop drilling bolt holes for the deck connections, which significantly reduces
the field work (i.e. overhead match drilling these holes).
o Provide a clean, smooth top flange that yields a more uniform bearing and faying
surface.
o Eliminate pitting from previous surface corrosion that retains moisture and is conducive
to corrosion development.
o Eliminate need to exercise care in removing the existing steel open grid deck and
corresponding extensive grinding of stringer top flanges to remove residual weld and
base metal, which greatly reduces construction duration.
o Yield higher quality stringers.
o Permits optimization of the floor system with elimination of some stringers.
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Existing stringers supporting the concrete filled steel grid deck over the machinery areas require
lowering by 2 inches to address difference in height between the 3‐inch existing deck and new
5‐inch deck.
The rack frames that support the concrete filled deck (bridges with Hopkins frame drive
machinery) require that the top flanges be lowered by removing and reattaching the top flange,
and trimming the top of the web.
Removal of spacer bars from the top of the existing floorbeams and main girders is not required,
but is recommended to eliminate unnecessary loose contact between the FRP composite deck
and steel framing.
Minor modifications to the counterweight including saw cutting and grouting at the transition to
the FRP composite deck.
Wearing Surface: The FRP composite deck requires a lightweight skid resistant wearing surface that
bonds well to the top faceplate. Currently only the thin epoxy polymer wearing surface meets these
requirements with:
Several manufacturers with similar products that permits competitive bidding opportunities,
Unit weight of 3 to 4 psf for two‐layer system with ¼” total thickness,
Good skid resistance (0.8 to 0.9 friction coefficient),
Shop application of large sections and field touch‐up at welded joints,
Ability to easily replace and repair surface,
Significant experience in similar applications, but
Limited service‐life (10 to 15 years) requiring period removal and reapplication.
(See Section 3 Wearing Surface Evaluation for more specifics).
Traffic Railings: No crash‐testing has been performed in accordance with NCHRP 350 for traffic railings
attached to the ZellComp or any other FRP composite decks to date. If a crash‐tested railing attached to
the deck is required, the approval will need to be on the basis of structural equivalence or crash testing
will need to be performed. Research has been initiated through ongoing projects to investigate
connections that will enable approved crash tested railings to be attached to the FRP decks. Limited
static testing has been performed that simulates vehicular impact loads on both concrete barriers and
steel rails attached to an FRP composite deck. However, this research is not in accordance with the
requirements of NCHRP 350. The performance of the ZellComp FRP composite deck for vehicular impact
loads applied to a traffic railing post is not clear.
Weight and Balance Requirements: Due to small differences in the unit weight of the existing deck and
new deck, the counterweight will require some adjustment. Because the weight of the new deck is very
similar to the typical steel open grid deck, adjustments can likely be made by adjusting the balance
blocks. Other modifications to offset the weight are not anticipated.
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2.3.8 Constructability
Fabrication: The FRP composite deck panels will be fabricated at the FRP composite manufacturing
facility. The pultruded sections will be cut to length. Where the stringers are to be replaced in
conjunction with the deck replacement, the panels will then be mated up to the supporting stringers
and main girder support angles in an inverted assembly layout (i.e. the panels and stringers oriented
upside down) to permit match drilling of the holes for the connections and splices. The Rivnuts will then
be installed in to the panels. The wearing surface may also be shop applied to the panels.
Tolerances on panel length, width, camber, sweep, squareness and flatness will generally be similar to
that of steel open grid deck. Flexibility of the FRP panels permits panel adjustment to address
tolerances in sweep, squareness and camber. The use of standard oversize holes in top flange of the
stringers and main girder supports will assist in accommodating small differences between shop and
field alignment.
Field Installation: The existing steel open grid and stringers will be removed. The main girder and
floorbeam spacer bars will also be removed and the rack frames and counterweight girder top flanges
modified as required. The new stringers and main girder support bars will be installed. Final drilling of
the holes in the webs of the floorbeams for the stringer connection angles will be performed after the
panels are aligned to the stringer top flanges. Shims between the stringer connection angles and
floorbeam webs will be provided for adjustment. Removal of the existing rivets and final drilling of the
holes in the horizontal legs of the new supports at the main girder top flanges (or field welding of the
supports if permitted) will be performed with the panels aligned to the supports.
Specialized Inspection: FRP composite materials, Rivnuts and thin epoxy polymer wearing surfaces are
less common to the bridge industry and thus inspection of this construction will, at least initially, be
considered specialty in nature.
The FRP composite manufacturer will be required to perform quality control and submit certifications
and a quality control plan that addresses the required quality control functions to be performed.
Because of the special requirements of the FRP composite fabrication, it may be necessary to employ
personnel with specialized experience to perform quality assurance for this work.
Rivnut installation and Rivnut bolt tightening quality control procedures will need to be developed. Field
welding of main girder supports if permitted will require on‐site involvement by welding inspectors. The
contractor will be required to submit weld procedure specifications and certifications for the field
welding. Quality control procedures for the wearing surface will also need to be developed and
employed.
Because of the complexity of the FRP composite material, potential degradation of deck strength and
stiffness from environmental and loading effect that can occur without obvious visual signs, and the
presence of a wearing surface that can obscure the top of the deck, specialized non‐destructive
examination techniques are required to periodically inspect and evaluate the deck. There are a number
of available non‐destructive examination methods that can be used to perform this inspection including:
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Visual Inspection,
Tap Testing (i.e. Sounding),
Thermal Testing ,
Acoustic Testing,
Ultrasonic Testing,
Radiography,
Modal Analysis,
Load Testing.
From NCHRP Report 564, Table below shows the various inspection methods that correlate to the types
of defects they can help detect.
Traffic Control: Because the FRP composite deck panels will be oriented with the long dimension
perpendicular to the roadway centerline similar to steel open grid panels, there is an opportunity to
replace portions of the deck (i.e. one floorbeam bay at a time in lieu of the entire deck) during short
duration (overnight) closures of the bridge in order to minimize traffic impacts. There are also
opportunities to replace the deck in phases in order to maintain traffic on the bridge while the work is
performed. The modular fabrication of the panels permits the panels to be fabricated in a size (length,
width and thickness) that closely matches that of the existing steel open grid panels to be replaced.
Small openings between the existing steel grid panels and the new FRP composite panels due to small
differences in panel dimensions can be temporarily covered with a thin plate. Joints in the panel along
the roadway centerline can permit the panels to be replaced in two halves with traffic maintained on
the opposite half. Details may need to be developed to accommodate bolting of temporary traffic
railing to the FRP composite deck panels, but these traffic railings will not likely be crash tested.
2.3.9 Costs
Construction Costs: The cost of the FRP composite deck system is anticipated to be significantly higher
than the cost to replace steel open grid roadway flooring (i.e. approximately two times the cost). The
cost can vary due to a number of factors and depends on the modifications required to fully implement
the deck system. This anticipated work includes a number of items including:
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Removal and disposal of the existing steel open grid and concrete filled deck,
Fabrication and installation of the new aluminum deck panels,
Replacement of the stringers including end connections,
Removal of the main girder spacer bars and installation of new supports including replacement
of some of the top flange rivets with high strength bolts or field welding the supports,
Installation of the wearing surface,
Minor modifications to the counterweight including saw cutting and grouting at the transition to
the aluminum deck,
Adjustment of balance blocks,
Span balance including detailed balance calculations, and instrumentation and recording of the
balanced condition before and after the work,
Adjustment of the live loads shoes in conjunction with the deck alignment,
Adjustment of the span locks in conjunction with the live load shoe adjustments,
Possible modification of the top of the rack frames (bridges with Hopkins frame drive systems
and where the rack frame supports the deck),
Traffic control,
Mobilization work.
Maintenance Costs: The cost to maintain the FRP composite deck is anticipated to be similar to that of
the steel open grid roadway flooring. Many maintenance activities will be eliminated or significantly
reduced, while other maintenance activities will be added.
Reduced maintenance activities include:
Reduction in the frequency of required cleaning and painting of the bascule leaf steel, as the
solid deck better protects these elements,
Elimination of the need to periodically repair broken steel open grid attachment welds,
Elimination of need to periodically repair cracked secondary and tertiary grid bars,
Elimination of the need to periodically improve skid resistance of steel open grid (e.g.
scarification of top surface),
Reduction in the future replacement of the deck.
Added maintenance activities include:
Periodic repairs or replacement of the wearing surface (e.g. thin epoxy polymer wearing
surface).
Due to great strength to weight ratio, corrosion resistance and durability of the FRP decks, savings in
deck replacement and maintenance costs over a service life could be much greater than the initial cost
of the entire structure. Temperature issue with reduction in stiffness can be a down side of FRP deck,
which will increase maintenance of FRP deck throughout the service life of FRP deck.
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The life cycle cost savings can be shown to more than offset the relatively high initial cost of the FRP
materials compared to conventional material. However, long‐range durability claims are viewed by the
construction industry with some skepticism.
Design Cost: The design cost is anticipated to be slightly more than that for replacement with steel open
grid deck, at least initially, as the design community becomes more comfortable with the design and
details, develops design skills and work product (plans and calculations) that can be adapted for use on
multiple projects.
Salvage Cost: The salvage value for FRP composite deck will generally be non‐existent. Although many
of the Florida bascule bridges are of a similar configuration, it will be difficult to remove the panels from
one bridge and relocated them to another bridge without damaging the panels.
Inspection Cost: The inspection cost may be slightly higher than that required for replacement with steel
open grid deck, at least initially, as the construction community becomes more comfortable with the
quality control requirements for this new type of deck system and the unique materials.
2.3.10 References
AASHTO LRFD Bridge Design Specifications with Interim Revision, Fifth Edition, 2010, Washington, D.C.
Zihong Liu (2007), Testing and Analysis of a Fiber‐Reinforced Polymer (FRP) Bridge Deck, Ph.D.
dissertation, Virginia Polytechnic Institute and State University, Blacksburg, VA.
Jignesh Sudhir Vyas (2006), Development of a Simplified Finite Element Approach for FRP Bridge Decks,
M.S. Thesis, University of Central Florida, Orlando, FL.
Wael Alnahhal, Methee Chiewanichakorn, Amjad Aref and Sreenivas Alampali (2006), Temporal Thermal
Behavior and Damage Simulations of FRP Deck, Journal of Bridge Engineering.
Yin Zhang and C.S. Cai (2007), Load Distribution and Dynamic Response of Multi‐girder Bridges with FRP
Decks, Science Direct, Engineering Structures 29 (2007) 1676‐1689.
Matt Sams (2004), Broadway Bridge Case Study – Bridge Deck Application of Fiber‐Reinforced Polymer,
Journal of the Transportation Research Board, CD 11‐S, Transportation Research Board of the National
Academics, Washington, D.C.; 2005, pp. 175‐178.
Thomas Cousins, John Lesko, Prasun Majumdar and Zihong Liu (2009), Rapid Replacement of Tangier
Island Bridges including Lightweight and Durable Fiber‐Reinforced Polymer Deck Systems, Charlottesville,
VA.
Rita Rodriguez‐Ver, Nicolas Lombardi, Marcelo Machado, Judy Liu and Elisa Sotelino (2011), Fiber
Reinforced Polymer Bridge Decks, Purdue University, West Lafayette, IN.
Niket Telang, Chris Dumlao, Armin Mehrabi, Adrian Ciolko and Jim Gutierrez (2006), NCHRP Report 564 ‐
Field Inspection of In‐Service FRP Bridge Decks, Transportation Research Board, Washington, D.C.
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Isaac Howard (2002), Development of Lightweight FRP Bridge Deck Designs and Evaluations,
Morgantown, WV.
Vistasp Karbhari, Joannie Chin and David Reynaud, (2000), Critical Gaps in Durability Data for FRP
Composites in Civil Infrastructure, 45th International SAMPE Symposium and Exhibition, Volume 45, Long
Beach, CA, pp. 549‐563.
Riyad Aboutaha (2006), Innovative Hybrid Wearing Surfaces for FRP Bridge Decks, Syracuse University,
16th International Conference on Composite Materials, Kyoto, Japan.
Steven Lovejoy (2011), Oregon DOT’s FRP Bridge Decks.
Dan Richards, Ph.D., P.E., ZellComp FRP Decks, www.zellcomp.com
Jerome O'Connor, P.E., Bridge Composites, LLC, www.bridgecomoposites.com
Strongwell, www.strongwell.com
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2.4 ULTRA‐HIGH PERFORMANCE CONCRETE (UHPC) DECK
2.4.1 Description
Ultra‐High Performance Concrete (UHPC) is a material that has recently gained attention in the bridge
industry. UHPC provides a combination of superior properties including strength, ductility, durability
that permits design and construction of thinner sections and longer spans that are lighter and more
efficient, while providing improved durability and impermeability against corrosion, abrasion and
impact.
UHPC has potential to be used in an alternative deck design to replace steel open grid deck on Florida
bascule bridges. The high concrete compressive and tensile strength allows design and construction of a
lightweight waffle slab bridge deck with thin elements (slab and ribs). A UHPC waffle slab deck
reinforced with MMFX rebar was previously investigated by the Florida Department of Transportation
specifically for this use through a joint research project performed by Florida International University
(FIU) and University of Central Florida (UCF). The researchers indicated that the proposed waffle slab
will have a unit weight of 25 psf, although follow‐up research yielded a unit weight of 29 psf.
Materials: A lightweight concrete waffle slab can be designed and constructed using high performance
UHPC and MMFX reinforcing materials.
UHPC: UHPC is formulated from a proprietary material made by Lafarge North America under the
trademark Ductal and consists of steel fiber reinforced concrete with an optimized gradation of fine
powders and a very low water/cement ratio (less than 0.25). Two of the primary sources for these
enhancements are the finely graded and tightly packed nature of the concrete constituent materials and
the steel fibers which knit the material together after cracking has occurred. The constituent materials
making up UHPC are cement, silica fume (microsilica), ground quartz, fine sand, steel fibers, water,
superplasticizer, and accelerator admixture. UHPC only includes fine aggregates. The exclusion of
coarse aggregate yields a material with discontinuous pore structure that reduces liquid ingress and
significantly lower permeability. UHPC has good long‐term creep and shrinkage behavior, excellent
resistance to chloride ion penetration, and the ability to hold up well under freeze‐thaw testing.
Testing of UHPC material has typically demonstrated compressive strengths of 18 to 28 ksi, and
corresponding tensile strengths of 1.3 to 2.1 ksi, depending on the curing method used. The material
has the capability to sustain deformations and resist flexural and tensile stresses, even after initial
cracking. UHPC also typically utilizes more effective curing methods than those traditionally used to
achieve the superior properties.
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Composition of UHPC Mix
MMFX Reinforcing Steel: MMFX Technologies Corporation manufactures high‐strength and corrosion‐
resistant reinforcing steel for concrete structures. The MMFX2 reinforcing bars, which have a material
specification conforming to ASTM A1035 (Standard Specification for Deformed and Plain, Low‐carbon,
Chromium, Steel Bars for Concrete Reinforcement), are available in Grade 100 or Grade 120, and in all
standard rebar sizes (No. 3 thru No. 11). The use of MMFX reinforcing steel is primarily due to the
limited clear cover to the reinforcing steel that could be achieved with thin concrete elements (i.e. 1¼”
thick top slab with No. 4 Bars, 2” thick primary ribs with No. 7 bars, and 1½” thick secondary ribs with
No. 4 bars), which will not be sufficient for standard ASTM A615 Grade 60 reinforcing. Because of the
corrosion‐resistant material and elimination of coarse aggregate a minimum concrete cover of ½” was
determined to be acceptable. The higher Grade 100 or 120 MMFX bars also yielded smaller size
reinforcing bars than required using Grade 60 reinforcing, which allowed the thickness of the members
to be minimized.
MMFX has been used in a number of locations throughout the United States and Florida. MMFX was
used for the bridge deck reinforcement of the Jensen Beach Causeway Bridge in Martin County, Florida
for the Florida Department of Transportation.
Waffle Slab Configuration: Refer to Figure 2, which shows the Florida International University (FIU) test
panel schematic, and Figure 3, which shows the test panel being loaded to failure in the FIU research
lab.
Applications: UHPC waffle deck slabs have not previously been used on a movable bridge.
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Waffle Slab Schematics
Waffle Slab Load Testing
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2.4.2 Product Development and Corporate Information
UHPC research is ongoing in an effort to better understand the full capabilities of the material, apply it
to bridge construction, and utilize shapes that optimize both cost and strength. UHPC research in the
United States is ongoing by the Federal Highway Administration (FHWA) at the Turner‐Fairbank Highway
Research Center in McLean, Virginia. A number of universities have contributed to the research of
UHPC.
The structural behavior of this material is becoming more predictable as a result of the continuing
research and testing. However, because the research is new and ongoing, design and construction
specifications using UHPC have not been developed and published. Some of the structural applications
for UHPC related to bridge construction that have already been researched and tested include
prestressed girders, two‐way ribbed (waffle) deck slab, and pourable deck joints.
As this is a relatively new material, there has only been limited use in the United States. The first bridge
in the United States using UHPC as the main superstructure material was constructed in Wapello
County, Iowa in 2006. The superstructure for this single span bridge includes UHPC modified Iowa Bulb‐
Tess prestressed Girders. The Cat Point Creek Bridge in Richmond County, Virginia was the second
bridge in the U.S. to take advantage of UHPC. This ten‐span bridge was constructed with UHPC in
precast prestressed Bulb‐Tee girders and opened to traffic in 2008. The Jakway Park Bridge in Buchanan
County, Iowa used UHPC in new Pi‐girders, and opened to traffic in November 2008.
UHPC has been used more extensively in Europe, Australia, and Asia. Ductal Lafarge is one of the leading
suppliers of UHPC, both in the United States and internationally.
Research has also investigated use of UHPC in two‐way ribbed (waffle) slabs. Ductal provided assistance
the to the FIU/UCF research team for the waffle slab testing.
2.4.3 Recent Bridge Installations
UHPC waffle slab deck research, sponsored by FHWA, under the Innovative Bridge Research and
Deployment (IBRD) program and the Iowa Highway Research Board (IHRB), has included a trial deck
implementation on a bridge in Iowa. The world’s first bridge (and only constructed to date) with a UHPC
waffle slab deck is the Little Cedar Creek Bridge in Ottumwa, Wapello County, Iowa constructed in 2011.
The bridge is described as follows:
Two‐lane, 60 feet long x 33 feet wide single span bridge,
Fourteen (14) precast UHPC, two‐way ribbed (waffle), modular deck panels that measure 16 feet
long x 8 feet wide x 8 inches deep, with a 2½‐inch thick top slab, 5½‐inch deep x 3‐inch to 4‐inch
wide tapered ribs spaced at 2 feet on center in each direction,
Composite with five (5) UHPC Iowa Type B precast, prestressed beams spaced at 7’‐4” on center,
Cast‐in‐place UHPC closure pours between panels, and haunches to attach panels to beams,
Precast panels constructed inverted by Coreslab Structures, Inc., Omaha, Nebraska.
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Laboratory testing was performed on two (2) waffle slab deck panels included the following load tests:
Service load testing at center of panel (21 kips) and at panel transverse joint (28 kips)
Fatigue testing at center of panel (21 kips, 1 million cycles) and at panel transverse joint (28 kips,
1 million cycles)
Ultimate load at center of panel (48 kips) and at transverse joint (40 kips)
Punching shear at center of panel (155 kips)
Skid resistance
2.4.4 Florida Bascule Bridge Specific Solution
Deck Solution: Because the 8‐inch deep UHPC waffle slab deck system used on the Little Cedar Creek
Bridge was much heavier than could be accommodated on a typical Florida bascule bridge, a lighter,
thinner version of the UHPC waffle slab deck system was developed, tested and evaluated. This new
UHPC waffle slab deck system consisted of the following:
Precast UHPC, two‐way ribbed (waffle), modular deck panels that measure 5 inches deep, with
a 1¼‐inch thick top slab with MMFX No. 4 Bars at 4 inches on center transversely, 3¾‐inch deep
x 2‐inch wide transverse (main) ribs spaced at 12 inches on center with one (1) MMFX No. 7 bar,
and 1¾‐inch deep x 1½‐inch wide longitudinal (secondary) ribs at 16 inches on center with one
(1) MMFX No. 4 Bar,
Transverse span across existing steel stringers and main girders spaced at 4 to 4.5 feet on
center,
Composite with stringers, floorbeams, and main girders by way welded headed stud shear
connectors and grouted closure pour and/or pockets.
Preliminary calculation of the weight of the deck was performed using the above UHPC mix design and
waffle slab configuration including the weight of the embedded reinforcing steel and required haunches
at the supports and joints between panels corresponding to the steel framing arrangement for a typical
Florida bascule bridge. Cast‐in‐place concrete haunches at the supports were assumed to utilize a
lightweight concrete with a unit weight of 120 pcf to reduce the weight of this material. The thicker
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concrete section of the haunch permits the use of a lower strength material (i.e. compressive strength
of 5.5 ksi) for the haunch concrete. This calculation yielded a deck unit weight of 36 psf.
Subsequent refinement and optimization of the UHPC waffle slab configuration, including use of tapered
ribs and reduced panel haunch dimensions yielded a reduction in the estimated weight to 29 psf.
Structural Modifications: The following modifications to the bridge are required to implement the UHPC
waffle slab deck:
Existing stringers supporting existing steel open grid deck can be reused and remain as currently
configured. However, replacement of the stringers would:
o Eliminate pitting from previous surface corrosion that retains moisture and is conducive
to corrosion development.
o Eliminate need to exercise care in removing the existing steel open grid deck and
corresponding extensive grinding of stringer top flanges to remove residual weld and
base metal, which greatly reduces construction duration.
o Yield higher quality stringers.
o Permits optimization of the floor system with elimination of some stringers.
Addition of welded headed studs to top of stringers, floorbeams and main girders to achieve
composite behavior.
Existing stringers supporting the concrete filled steel grid deck over the machinery areas require
lowering by 2 inches to address difference in height between the 3‐inch existing deck and new
5‐inch deck.
The rack frames that support the concrete filled deck (bridges with Hopkins frame drive
machinery) require that the top flanges be lowered by removing and reattaching the top flange,
and trimming the top of the web.
Removal of spacer bars from the top of the existing floorbeams and main girders.
Deck Connection and Panel Splices: The precast deck panels are spliced and attached to the bascule leaf
steel framing by way of cast‐in‐place closure pours. Welded headed studs are installed in the top of the
stringers, floorbeams, and main girders to achieve composite behavior. The studs are located in the
closure pours and/or pockets in the deck panels. In order to reduce weight, the closure pour concrete is
to consist with lightweight concrete. Because the haunches and closure pours are full‐depth (5 inches
thick) lower strength (5.5 ksi concrete) can be used for this material.
Traffic Railings: No crash‐testing has been performed in accordance with NCHRP 350 for traffic railings
attached to the UHPC waffle slab deck to date. If a crash‐tested railing attached to the deck is required,
the approval will need to be on the basis of structural equivalence or crash testing will need to be
performed.
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Weight and Span Balance Requirements: The total weight of the UHPC waffle slab deck including
associated panel colure pours and connections is significantly heavier than the weight of the typical
existing deck to be removed. A deck that is heavier than the existing steel open grid deck will also
require additional counterweight ballast, equal to two to three times the net increase in weight forward
of the trunnion, to balance the leaf.
Limited capacity of the trunnion assemblies, limited available space in and around the counterweights,
and limited capacity of the main girders typically limit the total increase in weight that can be
accommodated.
There are often opportunities to offset some of the additional weight by replacing other components
with lighter components (although this unnecessarily increases the required modifications to the bridge
and cost of the project) including:
Replacement of the concrete filled portion of the deck with the proposed lightweight solid deck
will reduce the overall weight of the deck. However, because this deck is located close to the
trunnion, with more of the deck located back of the trunnion, the replacement does not
significantly reduce the required additional counterweight ballast.
Replacement of the stringers with lighter, more efficient sections and/or reduction in the
number of stringers.
Replacement of steel sidewalk grating with lighter aluminum sidewalk plate or planking.
Replacement of the steel sidewalk support members and cantilevered bracket bracing members
with aluminum members.
Replacement of steel curbs and/or median with ones made from aluminum.
Replacement of steel bridge railing with lighter crash tested aluminum railing (e.g. Edgerail).
There may be opportunities for additional refinement and optimization to reduce weight including
elimination, re‐spacing, and/or resizing of stringers, and re‐spacing and/or resizing of transverse and
longitudinal ribs. However, these refinements have not been validated by engineering and testing.
2.4.5 Functionality and Safety
Load Capacity: A UHPC deck designed to governing stress limits will have corresponding load carrying
capacity in excess of that required to support AASHTO LRFD HL‐93 Live Loads. The small increase in deck
weight resulting from the heavier UHPC deck is not anticipated to significantly reduce the capacity of
bascule span members. There are opportunities to increase the load carrying capacity the stringers,
floorbeams, and main girders by taking advantage of composite action between the UHPC deck and
these members.
Rideability: The UHPC deck surface will be profiled (i.e. planed) after construction to provide a smooth,
continuous riding surface with a surface roughness comparable to typical concrete pavement. Because
the UHPC deck has greater stiffness than the existing steel open grid deck and the deck will act
compositely with the stringers and main girders, deflections and vibrations will be significantly reduced,
which will further improve the quality of the ride.
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Skid Resistance: Skid resistance from the applied wearing surface will be similar to that of concrete
pavement.
Noise: The solid surface and the vibration dampening characteristics of the UHPC deck will significantly
reduce noise generated by tires in contact with the deck relative to steel open grid deck.
Bicycle Safety: The UHPC deck provides a solid riding surface for the roadway and shoulders with small
longitudinal open joints (less than ½” wide) located immediately adjacent to the curbs or barriers, which
will greatly improve bicycle safety. Transverse deck joints between the two bascule leaves and between
the bascule span and bascule pier will range from ¾” to 1½” in width, but should not be a concern for
bicyclists.
2.4.6 Durability and Service Life
Service Life: The high strength, low permeable UHPC material is generally anticipated to provide a long
service life. However, because UHPC waffle slab deck is relatively new (i.e. less than 10 years’
experience in bridge deck applications) there are no installations that confirm that this service life can
be achieved.
Fatigue Resistance: Although fatigue testing has been performed on UHPC waffle slab decks, with
positive results, the testing performed to date has been on decks with more substantial dimensions (i.e.
greater overall slab depth, top slab thickness, rib dimensions, etc.) than those proposed for the UHPC
waffle slab deck for use on a typical Florida bascule bridge. As such, it is not clear whether a deck with
less substantial elements will provide similar fatigue resistance.
Corrosion Resistance: The exclusion of coarse aggregate yields a material with discontinuous pore
structure that reduces liquid ingress and significantly lower permeability. UHPC has good long‐term
creep and shrinkage behavior, excellent resistance to chloride ion penetration, and the ability to hold up
well under freeze‐thaw testing.
Although UHPC material provides increased impermeability, concrete cover to the reinforcing steel,
required to achieve a lightweight solution, is much less than typical concrete cover used in other
concrete bridge decks (less than 1/2 inch vs. 2 inches). Construction tolerances are anticipated to further
reduce the cover. Construction joints between the precast panels and cast‐in‐place closure pours
introduce opportunities for leakage (i.e. access of water containing chlorides to the embedded
reinforcing steel and structural steel below.) Continuous deck systems on double‐leaf bascule bridges
are subject to tension stresses (due to cantilever support conditions of the main girders and localized
negative bending of the floor system over the intermediate floorbeams) that act to open the
construction joints. Because of the limited cover and opportunities for leakage, use of corrosion
resistant reinforcing steel (e.g. MMFX, stainless steel or hot dip galvanized reinforcing steel) is
recommended.
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Impact Resistance: No impact testing has been performed on the UHPC waffle slab deck. As such, the
impact resistance (i.e. resistance to punching from concentrated impact force) of the relatively thin (1‐
1/4‐inch thick) top slab is not clear.
Fire Resistance: With typical reinforced concrete structures, the concrete provides limited insulation of
the reinforcing steel. Reinforcing steel loses strength and stiffness when exposed to high temperatures
(900 to 1100 degrees F). Because the concrete cover of a UHPC waffle slab deck is minimal, the
concrete provides little protection of the reinforcing steel.
Similar to steel members, UHPC deck is likely to survive short duration fires and/or fires with lower
temperatures. Because the loss of strength is time‐dependent, panels may provide limited structural
support for loads on the deck during a fire (e.g. the vehicle on fire, emergency response vehicles and
personnel). If the deck panels lose strength during these events, the steel framing below may steel
provide some support to contain vehicles.
Only a substantial heat source, such as that from a roadway accident with ignited localized fuel spill, is
expected to threaten the integrity of UHPC deck.
Thermal Expansion: The coefficients of thermal expansion of UHPC concrete and steel are similar. As
such differential thermal movement between the deck and bascule leaf steel framing will not be a
concern.
Chemical Resistance: UHPC material provides excellent resistance to most chemicals.
Ultraviolet (UV) Light Resistance: UHPC material is not subject to degradation from UV light and there
are no coatings required for the deck system that can degrade.
2.4.7 Maintenance
Repair: There is limited experience with the field repair or replacement of UHPC Waffle Slab Deck. As
such, it is unclear whether effective short‐term localized repairs can be implemented with this deck
system. Theoretically, UHPC material can be repaired (e.g. patching of spalls) similar to conventional
concrete. However, the relatively thin deck elements of the proposed UHPC waffle slab deck introduce
potential questions as to the effectiveness of the repairs.
Although the modular construction of the precast UHPC Waffle Slab Deck panels makes replacement of
individual sections of the deck practical, the grouted haunches with welded headed stud shear
connectors complicates the replacement and will slow the replacement process. It is not clear whether
a damaged panel can be replaced in a short duration nighttime closure.
Periodic Maintenance: Similar to other concrete elements, the UHPC waffle slab deck does not require
periodic maintenance to ensure the long‐term service life of the material.
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2.4.8 Design
The design methodology of the UHPC waffle slab deck system uses simple closed‐form equations based
on conventional reinforced concrete design methodology. The validity of this approach is based on
limited testing. However, this approach has generally shown to be conservative.
Currently, the design provisions are not endorsed by AASHTO and there are no design provisions in the
AASHTO LRFD Bridge Design Specifications for UHPC or waffle slab deck systems.
2.4.9 Research
Laboratory testing was performed by Iowa State University on two (2) waffle slab deck panels for the
Little Cedar Creek Bridge including the following tests:
Service load testing at center of panel (21 kips) and at panel transverse joint (28 kips)
Fatigue testing at center of panel (21 kips, 1 million cycles) and at panel transverse joint (28 kips,
1 million cycles),
Ultimate load at center of panel (48 kips) and at transverse joint (40 kips),
Punching shear at center of panel (155 kips),
Skid resistance.
Florida International University (FIU) performed laboratory tests on the Florida bascule bridge specific
UHPC waffle slab deck sections including the following:
Ultimate load testing of four (4) individual component strips (i.e. T‐beam with single rib and
corresponding 12‐inch wide deck slab) with three (3) different rebar anchorage details in a
simple span configuration supported on steel beams spaced at 4 feet on center with single load,
Ultimate load testing of four (4) individual component strips (i.e. T‐beam with single rib and
corresponding 12‐inch wide deck slab) with in a two span configuration supported on steel
beams spaced at 4 feet on center with two loads,
Ultimate load testing of three (3) 36‐inch wide panels (i.e. three (3) transverse ribs and
corresponding deck slab and longitudinal ribs) in a two span configuration supported on steel
beams spaced at 4 feet on center with two loads.
2.4.10 Constructability
Fabrication: The precast UHPC waffle slab deck panels will be fabricated at a precast manufacturing
facility licensed to use the proprietary Ductal UHPC material. Because of the limited concrete cover with
the thin elements, much stricter control of the reinforcing steel and concrete form dimensions will be
required. Panels will be fabricated in the inverted position to achieve high quality riding surface.
Specialized panel curing methods will be implemented as required to meet the specified physical
properties. Panels will need to be weighed after fabrication for use in balance calculations before
shipment.
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Field Installation: Because of the use of precast panels with limited available cover and the need to have
strict control on the weight of the deck, special care will be needed in field alignment of panels. Panels
will utilize temporary leveling bolts to support and align the panels. Additional forming around at the
stringer, floorbeam, and main girder haunches, and panel joints will be required. Lightweight concrete
closure pour concrete will be placed and cured.
Traffic Control: Because the UHPC waffle slab deck panels will be oriented with the long dimension
perpendicular to the roadway centerline similar to steel open grid panels, there is an opportunity to
replace portions of the deck (i.e. one floorbeam bay at a time in lieu of the entire deck). The tight
tolerances required with the deck field installation operations are anticipated to add time to the field
installation operations. As such, this construction may not be conducive to short duration overnight
closures, when considering all work involved. However, there are opportunities to replace the deck in
phases in order to maintain traffic on the bridge while the work is performed. The modular fabrication
of the panels permits the panels to be fabricated in a size (length, width and thickness) that closely
matches that of the existing steel open grid panels to be replaced. Small openings between the existing
steel grid panels and the UHPC waffle slab deck panels due to small differences in panel dimensions can
be temporarily covered with a thin plate. Closure joints in the panel along the roadway centerline can
permit the panels to be replaced in two halves with traffic maintained on the opposite half. Details may
need to be developed to accommodate bolting of temporary traffic railing to the UHPC waffle slab deck
panels.
Specialized Inspection: The use of proprietary UHPC material is less common to the bridge industry and
considered specialty in nature.
2.4.11 Costs
Construction Costs: The cost of the UHPC waffle slab deck system is anticipated to be significantly
higher than the cost to replace steel open grid roadway flooring (i.e. approximately two times the cost).
Because UHPC is a proprietary material, the material is available from a sole source. The cost can vary
due to a number of factors and depends on the modifications required to fully implement the UHPC
waffle slab deck system. This anticipated work includes a number of items including:
Removal and disposal of the existing steel open grid and concrete filled deck,
Fabrication and installation of the new precast UHPC waffle deck slab panels,
Field installation of the welded headed studs and haunch forms to stringers, floorbeams, and
main girders,
Removal of the main girder and floorbeam spacer bars,
Addition of ballast (e.g. adjustment blocks, concrete and/or steel ballast) secured to the
counterweight,
Span balance including detailed balance calculations, and instrumentation and recording of the
balanced condition before and after the work,
Adjustment of the live loads shoes in conjunction with the deck alignment,
Adjustment of the span locks in conjunction with the live load shoe adjustments,
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Modification of the top of the rack frames (bridges with Hopkins frame drive systems and where
the rack frame supports the deck),
Possible incidental work to offset the increased weight including replacement of sidewalk
grating, sidewalk supports, bridge railing, curbs and/or medians with lighter members,
Possible retrofit work to the trunnion assemblies to increase capacity including new trunnion
bearing bushings with higher strength bronze material or spherical roller bearings,
Traffic control,
Mobilization work.
Maintenance Costs: The cost to maintain the UHPC waffle slab deck is anticipated to be minimal. Many
bascule leaf maintenance activities will be eliminated or significantly reduced.
Reduced maintenance activities include:
Reduction in the frequency of required cleaning and painting of the bascule leaf steel, as the
solid deck better protects these elements,
Elimination of the need to periodically repair broken steel open grid attachment welds,
Elimination of need to periodically repair cracked secondary and tertiary grid bars,
Elimination of the need to periodically improve skid resistance of steel open grid (e.g.
scarification of top surface),
Reduction in the future replacement of the deck.
Added maintenance activities include:
Possible more frequent replacement of trunnion bearing bushings due to heavier loads on
bearings.
Salvage Cost: There is no anticipated salvage value for UHPC waffle slab deck.
Design Cost: The design cost is anticipated to be slightly more than that for steel open grid deck.
Because this deck system will be initially unfamiliar to the bridge design community, the cost of the
plans production will also be higher, until the design community becomes more comfortable with the
design and details, develops design skills and work product (plans and calculations) that can be adapted
for use on multiple projects.
Inspection Cost: The inspection cost may be slightly higher than that required for replacement with steel
open grid deck, at least initially, as the construction community becomes more comfortable with the
quality control requirements for this new type of deck system and the unique materials.
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Waffle Slab Panel Schematic (Modified for Typical Florida Bascule Leaf)
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UHPC Waffle Slab Details for Typical Florida Bascule Bridge (1 of 3)
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UHPC Waffle Slab Details for Typical Florida Bascule Leaf (2 of 3)
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UHPC Waffle Slab Details for Typical Florida Bascule Leaf (3 of 3)
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2.4.12 References
Keierleber, et. al. Design of Buchanan County, Iowa, Bridge Using Ultra High‐Performance Concrete and
Pi Beam Cross Section, 2008 PCI National Bridge Conference.
Mirmiran, A. & Mackie, Kevin (2011), Alternatives to Open Steel Grid Decks (Presentation dated
9/28/11).
Saleem, Mirmiran, Xia, and Mackie (2010), Alternative Deck System for Moveable Bridges, 2010 ASCE
Structures Congress (pp. 403‐416).
Wipf, et. al. (2009), Design and Evaluation of a Single Span Bridge using UHPC, Bridge Engineering
Center Tech Transfer Summary (September 2009), Iowa State University. <www.bec.iastate.edu>.
AASHTO (2010), AASHTO LRFD Bridge Design Specifications, 5th Edition (2010), American Association of
State Highway and Transportation Officials.
SDG (2012), FDOT Structures Design Guidelines (January 2012), FDOT Structures Manual, Florida
Department of Transportation, Structures Design Office.
Ductal‐Lafarge (2012), About Ductal, http://www.ductal‐lafarge.com/wps/portal/ductal/1‐
About_Ductal. Accessed February 24, 2012.
Ductal‐Lafarge (2012), Ductal Science Library, http://www.ductal‐lafarge.com/wps/portal/ductal/6_9‐
Technical_library. Accessed February 24, 2012.
MMFX Technologies Corporation (2012), About Us, http://www.mmfx.com/about.shtml. Accessed
February 24, 2012.
MMFX Technologies Corporation (2012), Product Line, http://www.mmfx.com/products.shtml.
Accessed February 24, 2012.
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3.0 WEARING SURFACE EVALUATION
3.1 INTRODUCTION
All of the alternative lightweight solid deck systems proposed to replace the steel open grid require the
use of a lightweight, skid‐resistant roadway wearing surface. As there are a number of available
products that meet this requirement, an evaluation of the wearing surfaces is warranted.
The lightweight solid deck alternatives under investigation include the Sandwich Plate System (SPS)
developed by Intelligent Engineering, aluminum orthotropic deck system developed by Sapa, and Fiber
Reinforced Polymer (FRP) deck system such as that developed by ZellComp. It was determined that
ultra‐high performance concrete (UHPC) waffle deck slab was too heavy to be considered a viable
lightweight deck alternative, and as a result, will not be considered as one of the substrate materials for
the deck overlays.
The primary function of the wearing surface is to provide a safe riding surface for vehicles crossing the
bridge by providing a slip‐resistant surface. The top surface of each of the proposed alternative deck
systems are not inherently skid resistant surfaces. In addition, the wearing surfaces should:
Minimize the weight added to the bridge,
Provide a relatively smooth and uniform riding surface,
Bond well to the substrate and provide sufficient flexibility to accommodate movement of the
deck and bascule leaf structure without cracking under:
o Expected loading conditions including wheel loads, traction and braking, thermal
restraint forces,
o Expected deformations including flexure of the deck from wheel loads and in‐plane
deformation of the deck from overall deflection of the bascule leaf steel framing and
thermal expansion and contraction,
Maintain integrity at the joints,
Protect the bridge deck top surface from a wide variety of environmental conditions including
exposure to typical chemicals deposited on the road including chlorides from the coastal
environment and exposure to ultraviolet light,
Resist polishing, abrasion, and wear from traffic and maintain the skid resistance,
Provide impact resistance such as that from a vehicular collision or metal objects dropped or
dragged from a moving vehicle),
Provide a relatively long service life,
Accommodate economical repair or replacement,
Have the capability of either shop or field application,
Have a history of use in similar applications.
There are a number of applied wearing surfaces that have been used on bridge decks including hot mix
bituminous asphalt, polymer concrete (e.g. latex modified concrete), and thin polymer overlays. This
report will not consider asphalt or polymer concrete overlays due to the required thick application of
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these materials and the corresponding weight. In addition, hot mix bituminous asphalt has a concern
with developing an adequate bond to the proposed substrates and polymer concrete generally lacks the
flexibility to accommodate the anticipated deformations without cracking. Hot spray applied metal
overlays have been used in pedestrian and bicycle applications but do not have a history of use in
roadway applications. However, as this type of overlay meets many of the evaluation criteria it will be
included in the evaluation.
Examples of wearing surface failures
The method of applying the overlay to the bridge deck will vary, depending on the type of overlay
selected, and will be summarized for each of deck overlay products evaluated in this report. The field
performance of the various overlay products has been documented in some cases in various research
projects, and will be discussed later in greater detail to determine what possible maintenance issues
may arise for each of the products when they are put into service.
After the unsuccessful use of hot mix bituminous asphalt and polymer concrete overlays on two bascule
bridges with that were retrofitted with FRP composite decks, the Oregon Department of Transportation
prepared an evaluation of four thin polymer overlays in 2005. This evaluation considered and ranked
the tensile strength, flexibility, bond strength, and wear resistance of these thin polymers.
3.2 ALTERNATIVE WEARING SURFACES
Initial screening of wearing surface overlays for the above evaluation criteria yielded two primary types
of products that have merit including: thin polymer overlays and hot‐spray applied metal overlays.
Further evaluation of the proposed wearing surface overlays included review of manufacturer product
data sheets and research papers.
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3.3 THIN POLYMER OVERLAY WEARING SURFACES
Thin polymer bridge deck overlays have limited use in the United States for 25 years and there are a
number of available products from different manufacturers that are available, each with slightly
material and physical properties and corresponding advantages and disadvantages.
Thin polymer overlays generally consist of a combination of polymer resin binder and stone aggregate,
which together form a single layer. The polymer overlay is usually applied in multiple layers (two or
three) using a “broom and seed” application method. Two‐layer overlays are typically range from 1/4”
to 3/8” thick. Common resin binders for a thin polymer overlays consist of epoxy, modified epoxy
(which includes epoxy urethane and polysulfide epoxy), or methyl methacrylate (MMA). More research
has been conducted on epoxy or modified epoxy resin products and there are a greater number of
epoxy resin products than MMA.
Thin polymer overlay products have been effectively applied to concrete, steel, aluminum and FRP,
bridge decks and are generally recommended by SPS, Sapa and ZellComp for use on their deck systems.
These products are generally expected to last a minimum of 15 years when properly applied per
manufacturer specifications. The average installed cost of the overlays is $15 to $20 per square foot of
deck area.
The products evaluated in this report are generally a sample of the thin polymer overlay products
currently available. Their inclusion with this report does not imply that their products are superior to
the others that have been excluded. The products shown in this report were evaluated primarily based
on documented previous use and research. Products reviewed include:
Transpo T‐48: A polysulfide epoxy based polymer concrete overlay manufactured by Transpo
Industries, Inc.
FLEXOGRID Mark‐163: A urethane modified epoxy polymer concrete overlay manufactured by
POLY‐CARB, Inc. (a subsidiary of the Dow Chemical Company).
Traficguard EP35: An epoxy‐based concrete overlay system manufactured by BASF.
(NOTE: The research performed by Oregon DOT concluded that a product using a urethane modified
epoxy polymer (URE‐FAST PF‐60 manufactured by URE‐FAST Industries, Ontario, Canada) yielded the
best combination of properties).
All three products can be applied using a broom‐and‐seed method in multiple layers, or using single
application slurry method. The epoxy resin is typically fast curing with typical cure times of 1.5 to 3.5
hours, depending on the ambient temperature, which is advantageous for traffic control purposes
where the roadway can be closed for only short durations (e.g. overnight closures). The overlay is not
overly sensitive to environmental conditions with a permissible ambient temperature at the time of
application typically between 50 and 100°F. The overlay can typically be applied to a finished thickness
of 1/4" to 1/2”. However, in order to minimize the added weight to the bascule span, it is
recommended that a maximum finished thickness of 1/4” be used, which corresponds to a unit weight
of 3 to 4 pounds per square foot.
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Steel, aluminum and FRP composite surface to receive the overlays must be cleaned and shot or grit
blasted to the requirements of SSPC‐SP10, with a minimum 4 mil (0.2 mm) anchor profile. If flash rust
appears, the surface must be cleaned and blasted again.
The coarse aggregate provides the skid‐resistance and wear resistance. The coarse aggregates typically
consist of clean, dry (less than 0.2% moisture content), sharp, angular, sound, non‐friable, abrasion
resistant, broken stone (e.g. silica (quartz) with Mohs scale hardness of 7 or basalt with Mohs scale
hardness of 6) aggregate may be used. The coarse aggregate is typically small (100% passing a #4 Size
sieve) and to a specified gradation.
The epoxy resins contain chemicals that can be considered hazardous (e.g. produce noxious fumes) and
thus require care in handling per documented material‐safety data sheets. Aggregates can include fines
that produce dust that can be an irritant.
The coarse aggregate is combined with the epoxy resin by broadcasting it onto already placed layer of
the epoxy resin with one of two methods:
Broom‐and‐seed Method: Usually associated with epoxy polymers, in this method, the mixed epoxy
resin is typically spread onto the substrate with a notched squeegee at a prescribed application rate and
in a continuous operation by applying the subsequent mixes immediately behind the preceding mixes.The aggregate is typically broadcast immediately onto the already placed epoxy resin to complete
saturation until a dry surface is re‐established. Additional layers are applied in a similar manner, but
typically within no more than 24 hours of the preceding layer. This method of application is susceptible
to contamination between applications from moisture, dust and debris if the structure must be opened
to traffic between layer applications. Anything trapped in the overlay between layers could result in
premature overlay failure. Multi‐layer overlay systems also exhibit some level of porosity which may
cause premature failure on either concrete or steel substrates.
Slurry Method: Usually associated with polysulfide epoxy polymers and MMA, slurry overlay systems
are made up of specially formulated resins having excellent physical properties and a uniquely
formulated slurry powder component that allows the overlays to be installed in thicknesses of 3/8” to
1/2” in a single application. This results in an overlay with virtually zero porosity preventing the egress of
moisture, chlorides, salt and other corrosion‐inducing substances. This process includes the application
of a primer coat on the surface using the same resin as the slurry component. Immediately after the
primer is installed the overlay slurry can be applied to the surface. The slurry is a mixture of the epoxy
resin and the prepackaged slurry powder component that is spread over the surface using gauge rakes,
preset to a specified thickness which will result in the specified overlay thickness to meet the project
requirements. The slurry is formulated so that it self‐levels within minutes after the gauge raking is
completed resulting in a smooth uniform surface. Once the slurry has leveled the surface is then covered
with the coarse broadcast aggregate. A seal coat is recommended with MMA to lock down the
aggregate.
The wearing surface is usually applied in the field, but can also be applied in a shop controlled
environment. Field application permits a continuously applied wearing surface with minimal cold joints.
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Shop application yields discontinuities in the wearing surface with small areas of field patching at the
bolted panel splices.
These products have been tested to meet a number of physical properties per various ASTM standards
including compressive strength, flexural strength, flexural modulus of elasticity, wet skid resistance,
tensile adhesion, tensile elongation, hardness, thermal compatibility, water absorption, chloride
permeability, abrasion, viscosity, gel time and pot life. The overlays are generally impervious and
prevent ingress of moisture, chlorides, salts and other corrosion inducing substances, are compatible
with concrete, steel, aluminum and FRP composites, exhibit relatively good elasticity, are resistant to
wear, have good bond with properly prepared and sound substrates, and are resistant to UV light. The
products have been used on concrete, steel and aluminum orthotropic, and FRP composite bridge decks.
3.4 HOT SPRAY APPLIED METAL OVERLAYS
Hot‐spray applied metal overlays have been used in limited applications within the bridge industry.
There are only a few products and suppliers (e.g. Slip‐NOT supplied by W.S. Molnar Company, and
Mebac supplied by Harsco Industrial). Although these products have received widespread as slip‐
resistant surfaces in pedestrian‐bicycle applications, these products have only been used in limited
application in roadway applications (e.g. SlipNOT has been applied to plates used to temporarily cover
holes in the roadway or bridge decks). The hot‐spray applied metal overlay products in this report
represent a sample of the products currently available in the market, and their inclusion with this report
does not imply that their products are superior to the others that have been excluded. Other metal
coating products that may have merit for bridge wearing surfaces include Carbinite (manufactured by
Carbinite Metal Coatings), and ALGRIP metal safety flooring (manufactured by Ross Technology
Corporation). Similar to SlipNOT and Mebac, the latter two products do not advertise as having been
previously used as a bridge wearing surface, but have properties that make them similarly viable for
similar use. For this report, the evaluation of hot‐spray applied metal overlays is based on the SlipNOT
product.
These products typically consist of aluminum oxide or steel grit hot‐spray applied to metal substrates
(steel or aluminum). Currently, application of the surface coating is performed only at the surface
coating supplier’s manufacturing facility to pre‐fabricated components. Field application and repair of
the surface coating is not currently available.
For SPS deck, the surface application may need to be applied to the top faceplate, prior to injecting the
elastomer core, to prevent damage to the core caused by heat from the hot‐spray application. It is not
clear what surface temperature will cause damage to the elastomer core. Testing for this specific
application has not been performed. The pre‐fabricated SPS deck panels or top faceplate will need to be
shipped to the surface coating supplier and returned to the SPS deck manufacturing facility for
completion of the panel fabrication.
For aluminum orthotropic deck, the deck panels will need to be shipped to the surface coating supplier
after fabrication.
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The hot‐spray applied metal overlay cannot be applied to an FRP composite due to the effect that the
high heat from the hot‐spray application would have on the material.
SlipNOT, manufactured by SlipNOT Metal Safety Flooring (a division of the W.S. Molnar Company) is
available in three different grades, with each grade varying in the coarseness of the metal aggregate.
The product is applied to the substrate using a patented process which applies a plasma stream
deposition of molten metal to a metal substrate creating a surface that has a bond strength of at least
4,000 psi and has a surface hardness of between 55 – 63 on the Rockwell “C” scale. The SlipNOT metal
surface can be steel, stainless steel, or aluminum, and is advertised as being applicable to either steel or
aluminum substrates. Grade 1 is a fine surface with a peak to valley surface depth of 0.010” to 0.012”, is
used in light duty applications, and is available for all surface types. Grade 2 is a medium surface with an
average peak to valley surface depth of 0.020” to 0.025”, and is the maximum coarseness available for
aluminum and stainless steel surfaces. Grade 3 is a coarse surface with an average peak to valley
surface depth of 0.032” to 0.038”, is used for heavy‐duty application such as vehicular traffic, and is only
offered as a steel surface. It is recommended by the manufacturer that this product be hot dipped
galvanized as well. The galvanized steel, Grade 3 option appears to be the best option for typical Florida
bascule bridges.
SlipNOT has been used in limited temporary roadway
applications on bridges such as the Ridgely Avenue
Bridge over Weems Creek in Annapolis, Maryland.
Temporary steel plates with SlipNOT were installed on
the bridge to temporarily widen the bridge deck to
accommodate traffic control during bridge
construction. The steel plates were removed after a
couple of years of use, and installed at another site.
The successful use of this product in a temporary
application indicates that use in a permanent
application may be practical. Additional testing to
demonstrate the long‐term durability and frictional
resistance of the wearing surface is warranted, in
recognition that the surfaces currently must be applied
in the shop (i.e. the deck panels would need to be
removed from the bridge and sent to the shop for re‐
coating if there is a significant loss in slip‐resistance or
other concerns with the wearing surface.
SlipNOT Road Plate on the Ridgely Avenue Bridge,
Annapolis, MD
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3.5 DECK OVERLAY PROPERTIES
The various properties functional, safety and durability properties for the thin epoxy polymer overlays
and hot‐spray applied metal coatings are described below.
Unit Weight: The unit weight of the wearing surface will have a significant effect on the bascule span
balance and overall weight of the bascule span.
Thin Epoxy Polymer Overlay: A two‐layer, thin polymer epoxy overlay with a thickness of 1/4” (which is
the minimum recommended thickness using a two‐layer application) typically yields a unit weight of 3 to
4 psf. A three‐layer overlay with a thickness of 3/8” (which is the minimum recommended thickness
using a three‐layer application) typically yields a unit weight of 5 to 6 psf. The two‐layer overlay is
recommended in order to reduce weight. However, a three‐layer system will typically have greater
durability and a longer service life.
Hot Spray Applied Metal Overlay: A hot‐spray applied metal coating (e.g. SlipNOT) will typically yield a
unit weight of 0.5 to 1.5 psf, depending on the surface texture (Grade 1: Fine, Grade 2: Medium, Grade
3: Coarse).
Skid Resistance: The skid resistance of a roadway surface is an important factor in vehicle safety as it
affects both stopping (braking) distance and lateral grip. The skid resistance of the wearing surface
should preferably be similar to the skid resistance of typical asphalt and concrete pavements in both wet
and dry conditions.
Skid resistance is tested on roadway pavement using a variety of standard tests that measure the
friction between the rubber tire of a vehicle and the pavement surface. Typical tests include ASTM
E1911 (“Standard Test Method for Measuring Paved Surface Frictional Properties Using the Dynamic
Friction Tester), ASTM E2157 (“Standard Test Method for Measuring Pavement Macrotexture Properties
Using the Circular Track Meter”), ASTM E2340 (“Standard Test Method for Measuring the Skid
Resistance of Pavements and Other Trafficked Surfaces Using a Continuous Reading, Fixed‐Slip
Technique”), and ASTM E274 (“Standard Test Method for Skid Resistance of Paved Surfaces Using a Full‐
Scale Tire”). The Florida Department of Transportation typically has used ASTM E274 to test the skid
resistance of steel grid decks in previous research.
Thin Epoxy Polymer Overlay: The initial skid resistance friction number (FN) of typical thin polymer
epoxy overlay products tested per ASTM E274 for wet conditions is 40 to 55 (i.e. coefficient of friction of
0.40 to 0.55). The skid resistance of epoxy polymer overlays is known to reduce somewhat over time as
the wearing surface is abraded and polishes.
Hot Spray Applied Metal Overlay: Skid resistance of vehicle tires on hot‐spray applied metal coated
surfaces has not been tested to date. The specified minimum slip resistance typically is a coefficient of
friction of 0.60. Measured coefficients of friction typically exceed 0.85 (wet and dry) but can vary
slightly depending on the surface grade, material and test performed.
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Service Life: The expected service life of the wearing surfaces is as follows:
Thin Epoxy Polymer Overlay: A properly specified and installed thin epoxy polymer wearing surface is
generally expected to provide a service life of 15 years before removal and replacement is required.
Hot Spray Applied Metal Overlay: The service life of a hot‐spray applied metal overlay as a roadway
wearing surface is not clear as testing has not been performed to demonstrate the wear resistance and
long‐term loss in skid resistance of the surface. It is anticipated that the wear resistance will dictate the
service life of this wearing surface. Because there currently is no available field application of the
coating and panels must be removed to the coating supplier shop for re‐coating, a long service life for
the wearing surface is needed to justify its use.
Wear Resistance: The ability of the wearing surface to resist wear, abrasion and polishing from
vehicular traffic is important to the safety and durability of the wearing surface.
Thin Epoxy Polymer Overlay: The coarse aggregate provides the largest contribution to skid‐resistance
and wear resistance. The coarse aggregates that are relatively hard, angular, sound, non‐friable and
abrasion resistant (e.g. silica (quartz) with Mohs scale hardness of 7 or basalt with Mohs scale hardness
of 6) exhibit good wear resistance. Higher quality coarse aggregates will generally provide greater wear
resistance and greater durability. A three‐layer system will have greater durability than a two‐layer
system because it takes a longer time for the thicker overlay to become worn to the layer of the
substrate. The coarse aggregates are typically tested for absorption, abrasion resistance and soundness.Aggregates used in epoxy overlays have a low absorption since moisture in the overlay can cause a loss
of adhesion between the epoxy and the aggregate and premature deterioration of the aggregate; a high
abrasion resistance so that the overlay can provide a high skid resistance over its life; and a high
soundness to resist deterioration when subjected to cycles of freezing and thawing.
Hot Spray Applied Metal Overlay: Wear resistance of vehicle tires on hot‐spray applied metal coated
surfaces has not been tested to date. The file hard surface coating (Rockwell C Scale Hardness of 55 to
63) is anticipated to yield good wear resistance.
Bond Strength: The strength of the bond between the wearing surface and the substrate is important to
ensure that the wearing surface does not delaminate and spall under the flexural deformations.
Thin Epoxy Polymer Overlay: Typical bond (adhesive) strength between thin epoxy polymer overlay and
the substrates is between 250 and 500 psi. The bond strength is dependent on the surface preparation
(SSPC‐SP10 surface finish for metal substrates) and anchor profile (shot or grit blast to minimum 4 mil
(0.2 mm) surface roughness).
Hot Spray Applied Metal Overlay: Typical bond (adhesive) strength between hot‐spray applied metal
coatings and steel substrates is greater than 4000 psi (except aluminum surface on aluminum substrates
which is greater than 2000 psi).
Ultraviolet Light Resistance: The wearing surface will be directly exposed to sunlight and corresponding
ultraviolet (UV) radiation that is known to cause degradation of many materials.
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Thin Epoxy Polymer Overlay: The epoxy polymer resins of thin epoxy polymer wearing surfaces have
been specifically formulated and tested to demonstrate to resist degradation from exposure to UV
radiation. The coarse aggregates are generally inert and do not degrade from exposure to UV radiation.
Hot Spray Applied Metal Overlay: The metals in the wearing surface of hot‐spray applied metal overlays
do not degrade from exposure to UV radiation.
Chemical Resistance and Corrosion:
Thin Epoxy Polymer Overlay: The dense epoxy polymer resin binders are generally impermeable and
thus penetration of chemicals including chlorides from saltwater to the metal substrate provided that
the wearing surface is not breached.
Hot Spray Applied Metal Overlay: The applied metal coating may or may not fully coat the substrate and
thus does not prevent chemicals including chlorides from saltwater from accessing the substrate. The coating itself does not protect from rust and corrosion; however aluminum, stainless steel and
galvanized steel products are generally corrosion resistant. Galvanized of steel coatings is
recommended to prevent corrosion of the steel substrate.
Tensile (Flexural) Strength: Good flexural strength and flexibility of the wearing surface is needed to
prevent development of cracking.
Thin Epoxy Polymer Overlay: The epoxy polymer resins are typically formulated with good physical
properties and can accommodate some flexural deformations without cracking. Physical properties
range significantly from product to product with some products providing greater strength and flexibility
than others.
Hot Spray Applied Metal Overlay: The hot‐spray applied metal coating does not significantly affect the
tensile (flexural) strength and stiffness of the metal substrates and because the coating is metallic it is
highly flexible.
Maintenance: Future maintenance, repair and replacement of the wearing surface must be considered
in the selection of the type of surface to be used.
Thin Epoxy Polymer Overlay: Complete repairs and localized repairs to thin epoxy polymer wearing
surfaces can be performed using the same material and application procedure used to originally apply
the material including surface preparation. In making repairs, all unsound material surrounding the area
to be repaired should be removed using mechanical means (e.g. scrapers and chippers).
Hot Spray Applied Metal Overlay: Field repair of hot‐spray applied metal coatings using the same
technology as the original supplier is not currently available. Panels must be removed and shipped back
to the coating supplier shop for repair or replacement. It is not clear whether it is practical to remove
the existing coating from the substrate or whether a new coating can be applied over the existing
coating or whether the deck panel must be replaced in the event of loss of skid resistance, or other
unacceptable deficiency.
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Field repairs of the substrate can be performed with the hot‐spray applied coating remaining intact. The
coating can be sheared, flame or torch cut or otherwise fabricated without harming the surface. Since
the coating is an all‐metal surface it can be welded, either directly or from the opposite side, without the
need of grinding or other surface preparation using the same standard metal welding rods. The coating
can also be drilled, countersunk and formed.
3.6 REFERENCES
Alampalli and Kunin (2001). Load Testing of an FRP Bridge Deck on a Truss Bridge, Report No.
FHWA/NY/SR‐01/137. Special Report 137, Transportation Research and Development Bureau, New York
State Department of Transportation.
Alger, Gruenberg, and Wegleitner (2003). Field Performance of Polymer Bridge Deck Overlays in
Michigan, Research Report RC‐1422. Michigan Department of Transportation, Construction and
Technology Division.
Fowler and Whitney (2011). Long‐Term Performance of Polymer Concrete for Bridge Decks, NCHRP
Synthesis 423. National Cooperative Highway Research Program, Transportation Research Board of the
National Academies.
Gama (1999). Durability of Epoxy Polymer Concrete Overlays for Bridge Decks, Master’s Thesis, McGill
University (Montreal, Canada), Dept. of Civil Engineering and Applied Mechanics.
Hall, et. al. (2009). Guide for Pavement Friction, NCHRP Project No. 01‐43. National Cooperative
Highway Research Program, Transportation Research Board (TRB) of the National Academies.
Izeppi, Flintsch, and McGhee (2010). Field Performance of High Friction Surfaces, Report No.
FHWA/VTRC 10‐CR6. Virginia Tech Transportation Institute, Center for Sustainable Transportation
Infrastructure.
Krauss, Lawler, and Steiner (2009). Guidelines for Selection of Bridge Deck Overlays, Sealers and
Treatments, NCHRP Project 20‐07, Task 234. National Highway Research Program, Transportation
Research Board.
Liang (2005). Performance of Polymer Concrete Wearing Surfaces on FRP Decks, Task 5.3.3, FHWA
Contract No. DTFH61‐01‐R‐00002. Federal Highway Administration, Office of Acquisition Management.
Pfeifer and Kowalski (1999). Evaluation of Thin Lift Polymer Bridge Deck Overlays on I‐57 Bridges at
Clifton, IL, Report No. IL‐PRR‐132. Illinois Department of Transportation, Bureau of Materials and
Physical Research.
Wilson and Henley (1995). Thin Polymer Bridge Deck Overlays, Report No. WA‐RD 374.1. Washington
State Department of Transportation, Bridge and Structures Office.
Zhang (1999). An Evaluation of the Durability of Polymer Concrete Bonds to Aluminum Bridge Decks,
Master’s Thesis, Virginia Tech University (Blacksburg, Virginia).
FPID 419497‐1‐B2‐01 Bascule Bridge Lightweight Solid Deck Retrofit Research
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Zimmer, Choubane, and Holzschuher (2003). A Friction Testing Method for Open Grated Steel Bridge
Decks, Paper submitted for presentation at the 2003 Transportation Research Board Annual Meeting.
Intelligent Engineering (2012). IE (Sandwich Plate System Bridge Decks) Home Page, http://www.ie‐
sps.com. Accessed February 28, 2012.
ZellComp (2012). ZellComp (FRP Bridge Decks) Home Page, http://www.zellcomp.com. Accessed
February 28, 2012.
Sapa (2012). Sapa (Extruded Aluminum Bridge Decks) Home Page, http://www.Sapa.com. Accessed
February 28, 2012.
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CONTRACT NUMBER ______________
LIGHTWEIGHT PREFABRICATED BRIDGE DECK SCOPE OF SERVICES
PROJECT BACKGROUND AND CONSIDERATIONS
In an effort to provide the traveling public of the State of __________ a cost effective, high
quality, transportation infrastructure, the _________________ Department of Transportation
(hereinafter referred to as the "Department") has adopted the following specifications for
performance based lightweight, prefabricated bridge decks. The Department intends to contract
for performance based prefabricated, lightweight bridge roadway and sidewalk flooring in order
to optimize various performance factors associated with the bridge deck. It is the intent of the
Department to solicit for competitive sealed proposals. Selection will be based upon a weighted
evaluation process that considers a written Technical Proposal and Price Proposal. The
Department intends to award this contract to the responsive and responsible Contractor that
receives the highest overall proposal score, calculated as the sum of the Technical Proposal
Score plus the Price Score.
OBJECTIVES
The Department is seeking to obtain durable, lightweight, prefabricated bridge roadway and
sidewalk flooring which meets or exceeds the Department's minimum performance standards,
and provides the best overall value.
(Insert the project description and limits here)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________
The scope of this project includes the removal and disposal of the existing bridge roadway and
sidewalk flooring, and the acquisition and placement of new bridge roadway and sidewalk
flooring which meets or exceeds the Department's performance specifications.
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GENERAL REQUIREMENTS
All work shall be performed in accordance with the Department's ______ Road and Bridge
Standards and Specifications. The Contractor will manage all work within the project limits and
will perform work that produces end results in accordance with Department Specifications
(including all Supplemental Specifications and Special Provisions), Design Standards, including
the Manual on Uniform Traffic Control Devices (MUTCD), American Society for Testing and
Materials (ASTM), and Code of Federal Regulations (CFR), in effect at the time of the
performance of the specific work, and consistent with the Department's statewide practices.
The Contractor shall adhere to all federal, state and local laws pertaining to proper health and
safety measures to ensure safety for the traveling public, Department employees, Contractor
employees, and Subcontractor employees. All claims and disputes by the Contractor shall be
resolved in accordance with the Department Standard Specifications and revisions thereto.
LIGHTWEIGHT, PREFABRICATED, BRIDGE DECK SPECIFICATIONS AND
PERFORMANCE REQUIREMENTS
Section 1 Description
The work under this section consists of furnishing and erecting roadway and sidewalk flooring
on bridge spans, including movable bridges, and at other locations as shown in the plans. The
flooring shall meet or exceed all of the performance requirements listed below.
1.1 Roadway Floor: Construct the roadway floor using an approved lightweight material. Steel
grated flooring shall be open metal grated with rectangular openings. Place and weld the steel
grated floor to the floor stringers as shown in the plans. As an alternative, provide an extruded
aluminum deck with a solid surface that meets the performance requirements. If the flooring
requires secondary or supplemental stringers, the Department will consider these stringers and
their fastenings a part of, and included, in the materials to be furnished and erected under this
section, and will consider any advantages to composite construction capabilities of the deck to
enhance bridge strength and capacity.
1.2 Sidewalk Floor: Erect sidewalk floor using an approved metal or other lightweight material.
Steel grid flooring shall consist of a metal grid with rectangular openings. The clear distance in
any opening shall not exceed 5/8 inches in one direction, and the longest dimension of any
opening shall not exceed 3 inches. As an alternative, provide an extruded aluminum floor that
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Page 3
has a solid surface and meets the performance requirements. Attach the floor to the supporting
members in accordance with the details shown in the plans, or in accordance with the
manufacturer's directions as approved by the Engineer.
1.3 Conformance with Manufacturer's Specifications: Meet the manufacturer's specifications
for material and construction methods, as approved by the Engineer, for the type of metal or
lightweight floor used.
1.4 Corrosion Protection: Metal bridge roadway and sidewalk floor materials shall be treated
with corrosion protection systems consistent with Department standards, and all coatings shall
be in accordance with Department standards. For steel grid flooring, all exposed areas of grid
floors shall have the same number, type, and thickness of paint coatings as are specified for
painted structural steel. Prepare the surface the same as required for painting structural steel.
If an extruded aluminum bridge floor is proposed, the Department will consider alternatives to
corrosion protection coatings when adequate material corrosion resistance can be
demonstrated by the Contractor and/or Manufacturer through recognized research and
documentation, to the Department's satisfaction.
1.5 Construction Details: Shop drawings shall be submitted to the Engineer for approval prior
to any fabrication or installation.
Section 2 Performance Criteria and Requirements
The Technical Proposal shall address the desired performance characteristics for the
lightweight bridge roadway and sidewalk flooring proposed for use under this specification,
including service life expectancy, enhanced live load carrying capability, structure dead load
characteristics, enhanced roadway width as a result of its lightweight and structural
characteristics, initial and long term quality, corrosion, ease of maintenance, speed of
construction, skid resistance/rideability, recyclability and safety.
2.1 Service Life Expectancy
The proposed bridge roadway and sidewalk floor shall meet Department standards and
specifications, and shall help to maintain the anticipated bridge service life. Materials and
methods that are demonstrated, to the satisfaction of the Department, to help extend the bridge
service life through anticipated enhanced material performance and reduced corrosion are
encouraged. The Contractor's Technical Proposal may be awarded additional points if the
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Page 4
proposed materials and methods are demonstrated, to the satisfaction of the Department, to
help extend anticipated bridge service life.
2.2 Live Load Carrying Capability
The proposed bridge roadway and sidewalk floor shall meet Department standards and
specifications, and shall not in any way reduce the structure's original design live load carrying
capability. Materials and methods that are demonstrated, to the satisfaction of the Department,
to increase the anticipated live load carrying capability (such as the deck working compositely
with the steel girders or stringers) of the structure are encouraged. The Contractor's Technical
Proposal may be awarded additional points if the proposed materials and methods are
demonstrated, to the satisfaction of the Department, to increase the anticipated live load
carrying capability of the bridge.
2.3 Structure and Dead Load Characteristics
The proposed bridge roadway and sidewalk floor shall not increase the structure's dead load
characteristics. Materials and methods that are demonstrated, to the satisfaction of the
Department, to reduce the structure dead load characteristics while maintaining or enhancing
performance (such as the deck working compositely with the steel girders or stringers) are
encouraged. In the case of movable bridge decks, materials and methods that help to meet
loading requirements as well as weight and thickness characteristics for movable bridge decks
are also encouraged. The Contractor's Technical Proposal may be awarded additional points if
the proposed materials and methods are demonstrated, to the satisfaction of the Department, to
reduce the structure's dead load and increase capacity rating.
2.4 Initial and Long Term Quality
The proposed bridge roadway and sidewalk floor shall provide initial and long term quality
through consistency in construction, functionality, ease of maintenance, and appearance.
Materials and methods that are demonstrated, to the satisfaction of the Department, to
maximize product quality, consistent quality, environmental control (including end of life
recyclability or reuseability), and increased quality control are encouraged. The Contractor's
Technical Proposal may be awarded additional points if the proposed materials and methods
are demonstrated, to the satisfaction of the Department, to increase the initial and long term
quality of the bridge floor.
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2.5 Corrosion
The proposed bridge roadway and sidewalk floor shall provide corrosion resistance and
protection in conformance with Department, ASTM, and manufacturer standards and
specifications. Materials and methods that are demonstrated, to the satisfaction of the
Department, to protect against and/or prevent corrosion of the bridge floor through enhanced
materials performance and reduced corrosion are encouraged. The Contractor's Technical
Proposal may be awarded additional points on a sliding scale to the degree that the proposed
materials and methods are demonstrated, to the satisfaction of the Department, to help protect
against corrosion throughout the bridge service life.
2.6 Ease of Maintenance
The proposed bridge roadway and sidewalk floor shall at a minimum restore floor condition such
that maintenance is minimized over the anticipated bridge service life. Materials and methods
that are demonstrated, to the satisfaction of the Department, to increase the ease of
maintenance through anticipated enhanced materials performance and reduced corrosion are
encouraged. The Contractor's Technical Proposal may be awarded additional points on a
sliding scale representing the comparative likelihood that the proposed materials and methods
are demonstrated, to the satisfaction of the Department, to ease maintenance.
2.7 Speed of Construction
The proposed bridge roadway and sidewalk floor shall at a minimum be installed in a manner
that meets all Department, ASTM, CFR, and manufacturer standards and specifications.
Materials and methods that are demonstrated, to the satisfaction of the Department, to minimize
on-site construction time; minimize traffic disruption; provide for less time spent on the site;
allow traditional tasks to be performed off-site; minimize impact from weather conditions; reduce
the need for detours, lane closures and narrow lanes; improve constructability through
prefabricated elements and systems; minimize impact from environmental constraints; relieve
constructability pressure; and/or reduce completion time are encouraged. The Contractor's
Technical Proposal may be awarded additional points if the proposed materials and methods
are demonstrated, to the satisfaction of the Department, to help speed construction by
minimizing on-site construction time; minimizing traffic disruption; providing for less time spent
on the site; allowing traditional tasks to be performed off-site; minimizing impact from weather
conditions; reducing the need for detours, lane closures and narrow lanes; improving
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Page 6
constructability through prefabricated elements and systems; minimizing impact from
environmental constraints; relieving constructability pressure; and/or reducing completion time.
2.8 Skid Resistance/Rideability
The proposed bridge roadway and sidewalk floor shall at a minimum meet Department and
ASTM standards and specifications for skid resistance/rideability. Materials and methods that
are demonstrated, to the satisfaction of the Department, to help improve skid
resistance/rideability are encouraged. The Contractor's Technical Proposal may be awarded
additional points if the proposed materials and methods are demonstrated, to the satisfaction of
the Department, to help improve skid resistance/rideability.
2.9 Safety
The proposed bridge roadway and sidewalk floor project shall meet Department, ASTM, and
CFR standards and specifications for safety. Materials and methods that are demonstrated, to
the satisfaction of the Department, to help improve work zone safety by minimizing work near
traffic and power lines, work at high elevations, and work over water, and/or improve safety for
the public, construction personnel, and inspectors are encouraged. The Contractor's Technical
Proposal may be awarded additional points if the proposed materials and methods are
demonstrated, to the satisfaction of the Department, to help improve project safety.
Section 3 Acceptance Criteria and Scoring 3.1 Contractor's Experience and Capabilities
The contractor's experience and capabilities will be evaluated and may be awarded up to a
maximum allowable score of 10 points.
3.2 Service Life Expectancy
The contractor's technical proposal may be awarded up to a maximum allowable score of 10
points based upon proposed materials and methods as demonstrated to help extend the
anticipated bridge service life.
3.3 Live Load Carrying Capability
The live load carrying capability shall be ___________ tons or better and the deck _______ feet
wider upon completion of the bridge deck project, as determined by signed and sealed
engineering calculations and as built drawings. A score of 7 points may be awarded for all
proposals meeting the minimum live load carrying capability. An additional point may be
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Page 7
awarded for each 10% increase in live load carrying capability and/or increase of width up to a
maximum of three additional points.
Live Load Points
xx to xx tons 7
xx to xx tons 8
xx to xx tons 9
xx or greater tons 10
3.4 Structure Dead Load Characteristics
The maximum structure dead load upon completion of the bridge deck project shall be no more
than 36 pounds per square foot. A score of 7 points will be awarded for all proposals meeting
the 36 pounds per square foot requirement. An additional point will be awarded for each 10%
reduction in dead load up to a maximum of three additional points.
Dead Load Points
36 to 32.4 lbs. per s.f. 7
32.3 to 29.2 lbs. per s.f. 8
29.1 to 26.2 lbs. per s.f. 9
26.1 or less lbs. per s.f. 10
3.5 Initial and Long Term Quality
The contractor's technical proposal may be awarded up to a maximum allowable score of 10
points based upon proposed use of long term quality products to maximize functionally,
environmental sensitivity, and appearance.
3.6 Corrosion
The bridge roadway and sidewalk floor shall be free from visible and/or detectable corrosion
upon project completion, and for a period of ___ years. The contractor's technical proposal may
be awarded up to a maximum allowable score of 10 points based upon proposed use of long
term quality products that have reduced corrosive effects.
3.7 Ease of Maintenance
The contractor's technical proposal may be awarded up to a maximum allowable score of 10 points
based upon proposed use of long term quality products to maximize ease of maintenance, and
reduced life cycle maintenance costs.
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3.8 Construction
Lane closures, lane restrictions, and/or detours shall not exceed a combined total of ___ days
during construction, shall comply with all Department standards, and shall be approved in
advance by the Department. A score of 3 points will be awarded for all proposals meeting the
number of maximum allowable lane closure, lane restriction, and/or detour days identified
above. An additional point will be awarded for each 10% reduction in number of total lane
closure, lane restriction, and/or detour days up to a maximum of seven additional points.
Lane Closures, Lane Restrictions,
and/or Detours Days Points
Maximum Allowed 3
10% Less than Maximum 4
20% Less than Maximum 5
30% Less than Maximum 6
40% Less than Maximum 7
50% Less than Maximum 8
60% Less than Maximum 9
70% Less than Maximum 10
3.9 Skid Resistance/Rideability
Friction testing will be performed in accordance with American Society for Testing and Materials
(ASTM) standardized test method ASTM E-274. Minimum skid resistance shall be ____ as
measured at ___ mph using ASTM E-274. (Reference: Texas Transportation Institute. (2002) A
Method for Friction Testing of Open Grated Steel Bridge Decks. College Station, Texas: Richard
A. Zimmer)
Skid Resistance/Rideability Points
xx to xx Skid Number 7
xx to xx Skid Number 8
xx to xx Skid Number 9
xx or greater Skid Number 10
3.10 Safety
The contractor's technical proposal may be awarded up to a maximum allowable score of 10 points
based upon work zone safety plans, minimization of impacts on traffic, and worker safety plans.
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Section 4 Contractor Proposal and Evaluation
The Contractor's proposal will contain two components, a Technical Proposal and Price Proposal.
4.1 Summary of Requirements for Contractor's Technical Proposal: The Technical
Proposal will address the requirements of the RFP and the Contractor's plans for accomplishing
tasks and achieving performance. An omission of any of the following required plans from the
Contractor's Technical Proposal will cause the proposal to be considered non-responsive. The
Contractor's proposal will be organized and presented in the same order as listed below:
1. Contractor Experience and Capabilities
2. Service Life Expectancy
3. Live Load Carrying Capability
4. Structure Dead Load Characteristics
5. Initial and Long Term Quality
6. Corrosion
7. Ease of Maintenance
8. Speed of Construction
9. Skid Resistance/Rideability
10. Safety
4.2 Technical Proposal Evaluation Criteria: The following technical proposal criteria and
corresponding maximum attainable point values are established for scoring the Technical
Proposals:
Technical Proposal Criteria
Maximum
Value
1. Contractor Experience and
Capabilities
10
2. Service Life Expectancy 10
3. Live Load Carrying Capability 10
4. Structure Dead Load Characteristics 10
5. Initial and Long Term Quality 10
6. Corrosion 10
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7. Ease of Maintenance 10
8. Speed of Construction 10
9. Skid Resistance/Rideability 10
10. Safety 10
Maximum Technical Raw Score 100
The raw score for the Technical proposal will be calculated by added the values assigned to
each of the technical proposal components listed above, and will be weighted as follows:
Technical Proposal Score = Raw Score for Technical Proposal X 100 X 0.80*
*weighted factor for technical proposal 80% = 0.80
Failure to obtain 70% of the available points on the Technical Proposal will disqualify the
Proposing Contractor’s entire proposal from further consideration. Price information for
disqualified proposals will not be considered, and the disqualified proposal will not be further
evaluated in the proposal selection process.
4.3 Pricing: Price analysis is conducted through the comparison of submitted price quotations.
Prices will be scored using the following pricing evaluation method:
Price Score = (Lowest bid price/Proposer's bid price) X 100 X 0.20*
*weighted factor for price proposal 20%=0.20
4.4 Overall Best Value Selection: The Department intends to select the Contractor meeting all
required criteria and having the highest total Proposal Score, as calculated below:
Total Proposal Score = Technical Proposal Score + Price Score
Section 5 Measurement and Basis of Payment
5.1 Method of Measurement: The quantities to be paid for will be the plan quantity, in square feet,
installed, complete and accepted. Proper deduction for open joints in the floor will be made in
calculating plan quantity.
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5.2 Basis of Payment: Prices and payments will be full compensation for all work specified in this
Section, including furnishing and installing the complete floor above the tops of the main floor
members shown in the plans, furnishing and installing any secondary joists which are required in
addition to the main floor members, furnishing and installing all coating materials, and welding.
Payment will be made under:
Item No. xxx-xx-x Lightweight Roadway Floor - per square foot.
Item No. xxx-xx-x Lightweight Sidewalk Floor - per square foot.