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S P R I N G 2 0 1 2

VETERANS MEMORIAL BRIDGEZumbrota, Minnesota

DELTA PONDS PEDESTRIAN BRIDGEEugene, Oregon

BENSON ROAD BRIDGERenton, Washington

THE BRIDGE AT PITKINS CURVEHighway 1 North of Limekiln State Park,

Monterey County, California

29 ROAD BRIDGE AND I-70B RAMPGrand Junction, Colorado

I-15 BECK STREET BRIDGESSalt Lake City, Utah

I-4/Lee Roy Selmon

Expressway InterchangeTampa, Florida
http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/http://www.aspirebridge.org/

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Bentley Systems Inc. . . . . . . . . . . . . . . . . . 19

CABA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

DSI/Dywidag Systems Intl-USA . . . . . . . . 31

Earthcam . . . . . . . . . . . . . . . . . . . . . . . . . . 35

FIGG . . . . . . . . . . . . . . . . . Inside Front Cover

Hanson Structural Precast . . . . . . . . . . . . 39

Headwaters Resources . . . . . . . . . . . . . . . . 41

Helser Industries . . . . . . . . . . . . . . . . . . . . 41

Holcim Cement . . . . . . . . . . . . . . . . . . . . . . 7

LARSA . . . . . . . . . . . . . . . . . . . . . . Back Cover

PB . . . . . . . . . . . . . . . . . . . Inside Back Cover

PCI . . . . . . . . . . . . . . . . . . . . . . . . . 3,5,53,55

Pile Dynamics Inc. . . . . . . . . . . . . . . . . . . . 56

Poseidon Barge Corp. . . . . . . . . . . . . . . . . 45

Safway . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Williams Form Engineering Corp. . . . . . . . 40

Advertisers Index

ASPIRE, Spring 2012|1

CON T EN T S

Photo: Caltrans.

Photo:PCLCivilConstructorsandArcherWesternConstruction,

jointventure.

Photo: MnDOT.

Photo: Jacobs Engineering Group Inc.

FeaturesCorven Engineering 8Corven Engineering stays true to its roots while leveraging its

expertise to maximize potential.

Veterans Memorial Bridge 16Ample new access provided for pedestrians, snowmobiles,

cars, and the Zumbro River.Delta Ponds Pedestrian Bridge 20Extending a sustainable transportation network.

Benson Road Bridge 24Extending precast concrete spans with Washington StatesSuper Girders.

The Bridge at Pitkins Curve 28One less bend in the road.

29 Road Bridge and I-70B Ramp 32A grand connectivity improvement in the Grand Valley.

I-15 Beck Street Bridges 36

A tectonic shift in bridge design.

DepartmentsEditorial 2

Concrete Calendar 4

Reader Response 6

PerspectiveA Contractors Point of View 12

PerspectiveAn Owners Viewpoint 14

Aesthetics Commentary 23

CCCLittle Cedar Creek Bridge 27StateMichigan 42

CCCFort Benning Gateway Bridge 46

Safety and Serviceability 48

FHWAResilience of Concrete Highway Bridges 50

CCCGeosynthetic Reinforced SoilBridge Abutments 52

Concrete Connections 54

AASHTO LRFDA Question of Applicationand Interpretation 56

16

32

28

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4/602|ASPIRE, Spring 2012

EDITORIALExecutive Editor

John S. Dick

Managing Technical EditorDr. Henry G. Russell

Managing EditorCraig A. Shutt

Editorial AdministrationJames O. Ahtes Inc.

Art DirectorPaul Grigonis

Layout DesignTressa A. Park

Ad SalesJim Oestmann

Phone: (847) 838-0500 Cell: (847) 924-5497Fax: (847) 838-0555 [email protected]

ReprintsPaul Grigonis

(312) 360-3217 [email protected]

PublisherPrecast/Prestressed Concrete Institute

James G. Toscas, President

Editorial Advisory BoardWilliam N. Nickas,Precast/Prestressed Concrete

Institute (PCI)

William R. Cox,American Segmental Bridge Institute

(ASBI)

Dr.David McDonald,Epoxy Interest Group (EIG)

Dr. Henry G. Russell,Henry G. Russell Inc.

John S. Dick, J. Dick Precast Concrete Consultant LLC

POSTMASTER

Send address changes toASPIRE200 W. Adams St., Suite 2100 Chicago, IL 60606.Standard postage paid at Chicago, IL, and additionalmailing offices.

ASPIRE (Vol. 6, No. 2),ISSN1935-2093is published quarterlyby the Precast/Prestressed Concrete Institute200 W. Adams St., Suite 2100 Chicago, IL 60606.

Copyright 2012, Precast/Prestressed Concrete Institute.

If you have a project to be considered forASPIRE, sendinformation toASPIRE200 W. Adams St., Suite 2100 Chicago, IL 60606phone: (312) 786-0300

www.aspirebridge.org [email protected]

CoverI-4/Lee Roy Selmon Expressway InterchangeTampa, FloridaPhoto: PCL Civil Constructors and Archer WesternConstruction, joint venture.

Evolution in Project Delivery Underway

With the increasing demand for transportationinfrastructure improvements, and the growing

inability to fund them, interest in alternative delivery systemscontinues to grow. Public-private partnerships, or P3s, arebecoming more attractive to help solve these needs. Thisissue includes two perspectives on the subject that willinterest bridge designers nationwide.

P3s take several forms including design-build, design-build-operate (and often maintain), and design-build-

finance-operate (and maintain). All result in greater privatesector participation in the delivery and, where applicable,

financing of transportation projects. All enable ownersto transfer risk associated with design and construction

and, in the latter two methods, with life-cycle performance,operations, and maintenance.

Presently, 23 states have enacted statutes that enablevarious P3 approaches for the development of transportationinfrastructure. Numerous projects have been completedor are presently underway. The typical projects range incost from about $50 million to more than $2.6 billion.Much information can be obtained on the Federal Highway

Administrations Innovative Program Delivery website,http://www.fhwa.dot.gov/ipd/index.htm.

The two perspectives in this issue on P3s come froma builder and a state agency who have both engaged inlarge P3 projects. The first, Public-Private Partnerships:

A Guide for Infrastructure Designers and Contractors bythe Flatiron Construction Corp. begins on page 12 and thesecond, Virginias Public-Private Partnership Program isOpen for Business is onpage 14.

In the Summer issue ofASPIRE, a follow-up articlewill delve into some of the financial and legal issues that

appear to be standing in the way of these new systems.You might wonder whyASPIRE is venturing into these

waters. New delivery methods will continue to play anincreasingly critical role in delivering the nations complex

infrastructure. Only a limited number of agencies and asmall segment of the concrete industry have had exposure tothis changing business climate to date, but many more willbecome familiar with it in the future.

In these systems, alliances and teams form early. Equitypositions on these teams will often control the selectionof materials for the bridge. We intend to help inform allstakeholders in the concrete bridge industryfromthe owner agencies to the builders, subcontractors, and

fabricatorsabout the options and the projects that takeadvantage of these new approaches.

To ensure concrete remains the bridge industrys materialof choice, it will be necessary to remain dedicated, vigilant,and proactive to the changes occurring in the industry.

Concrete provides many benefits including: Adaptability to unique and demanding

geographical challenges Systems that allow an enviable range of rapid

construction solutions

Reliable, and usually local supply sources atpredictable prices

Unparalleled resistance to the ravages of theenvironment

Beauty in form and functionTo continue to realize beautiful, long-lasting concrete

bridges, all stakeholders in the concrete supply chain need

to be cognizant of these new relationships. We are confidentthat concretes inherent values will ensure it remains the

preferred structural material for bridges.Two projects featured in this issue also were constructed

using the design-build method which continues to grow inpreference among many bridge stakeholders: the BensonRoad Bridge over I-405 beginning onpage 24 and theI-15 Beck Street Bridges starting onpage 36. The formeris another example of the use of concrete components toaccelerate bridge construction.

Photo: Ted Lacey Photography.

John S. Dick,Executive Editor

Precast/PrestressedConcrete Institute

On a Personal NoteThis is the 22nd issue ofASPIREsince we began publishing with the Winter issue in 2007. Having been involved

with conceptualizing the magazine and producing each of those issues has been an educational and enrichingexperience for me. Now, I am about to take on a new challenge called retirement. The production team andEditorial Advisory Board shown in the column to the right have been a delight to work with. They have taught mea great deal, and I embrace their friendship. The team is poised to carry on with some new blood at the top of themasthead. The tremendous success Ive experienced with theASPIREteam during our first 5 years has been due to

you, our readers and advertisers. Please continue to support ASPIREas I will. Thanks to all of you for your input,contributions, and support!

American SegmentalBridge Institute EpoxyInterest Group Silica FumeAssociationExpanded Shale Clayand Slate Institute Portland CementAssociation Post-TensioningInstitute
mailto:[email protected]:[email protected]://www.aspirebridge.org/mailto:[email protected]://www.fhwa.dot.gov/ipd/index.htmhttp://www.pci.org/http://www.pci.org/http://www.asbi-assoc.org/http://www.asbi-assoc.org/http://www.epoxyinterestgroup.org/http://www.epoxyinterestgroup.org/http://www.silicafume.org/http://www.silicafume.org/http://www.escsi.org/http://www.escsi.org/http://www.cement.org/bridgeshttp://www.cement.org/bridgeshttp://www.post-tensioning.org/http://www.post-tensioning.org/http://www.post-tensioning.org/http://www.cement.org/bridgeshttp://www.escsi.org/http://www.silicafume.org/http://www.epoxyinterestgroup.org/http://www.asbi-assoc.org/http://www.pci.org/http://www.fhwa.dot.gov/ipd/index.htmmailto:[email protected]://www.aspirebridge.org/mailto:[email protected]:[email protected]

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CONCRETE CALENDAR 2012/2013CONTRIBUTING AUTHORS

M. Myint Lwinis director

of the FHWA Office of Bridge

Technology in Washington,

D.C. He is responsible for the

National Highway Bridge

Program direction, policy, and

guidance, including bridge

technology development,

deployment and education, andthe National Bridge Inventory

and Inspection Standards.

Matt Girardis executive

vice president of business

development at Flatiron

Construction. He is engaged in

the emerging North American

P3 market, leading business

development efforts on more

than $5 billion of design-build

work for P3 projects.

Christie DeLucais

communications manager

at Flatiron Construction. She

has led the companys internal

and external communications

for nearly 10 years and

writes frequently about the

construction industry.

Dusty Holcombeserves

as deputy director of the

Commonwealth of Virginias

Office of TransportationPublic-Private Partnerships

where he administers the daily

operations of the Public-Private

Partnership program.

Dr. Dennis R. Mertzis

professor of civil engineering

at the University of Delaware.

Formerly with Modjeski and

Masters Inc. when theLRFD

Specificationswere first written,

he has continued to be actively

involved in theirdevelopment.

Frederick Gottemoeller

is an engineer and architect,

who specializes in the aesthetic

aspects of bridges and highways.

He is the author ofBridgescape,

a reference book on aesthetics

and was deputy administrator

of the Maryland State Highway

Administration.

April 16-17, 2012ASBI 2012 Grouting CertificationTrainingJ.J. Pickle Research CampusThe Commons Center

Austin, Tex.

May 6-8, 2012Post-Tensioning Institute AnnualConventionLoews Vanderbilt HotelNashville, Tenn.

May 7-10, 2012International ConcreteSustainability ConferenceRenaisssance Hotel

Seattle, Wash.

May 20-25, 201214th International Conferenceon Alkali-Aggregate Reactions inConcreteHyatt Regency AustinAustin, Tex.

June 10-13, 2012International Bridge ConferenceDavid L. Lawrence Convention Center

Pittsburgh, Pa.

July 7-12, 20122012 AASHTO Subcommittee onBridges and Structures MeetingHyatt RegencyAustin, Tex.

July 23-27 (Tentative)2012 PCA Professors WorkshopPCA HeadquartersSkokie, Ill.

September 29-October 2, 2012PCI Annual Convention andExhibition and National BridgeConferenceGaylord Opryland Resort & ConventionCenterNashville, Tenn.

October 3-5, 2012PTI Committee DaysThe Inn at St. JohnsPlymouth, Mich.

October 21-25, 2012ACI Fall ConventionSheraton CentreToronto, Ontario, Canada

October 29-30, 2012ASBI Annual ConventionTurnberry Isle Hotel & ResortMiami, Fla.

January 13-17, 201392nd Annual MeetingTransportation Research BoardMarriott Wardman Park, OmniShoreham, and Hilton WashingtonWashington, D.C.

February 4-8, 2013World of Concrete 2013Las Vegas Convention CenterLas Vegas, Nev.

April 14-18, 2013ACI Spring Convention

Hilton & Minneapolis Convention CenterMinneapolis, Minn.

September 21-24, 2013PCI Annual Convention andExhibition and National BridgeConferenceGaylord Texan Resort and ConventionCenterGrapevine, Tex.

October 20-24, 2013

ACI Fall ConventionHyatt and Phoenix Convention CenterPhoenix, Ariz.

For links to websites, email addresses, or telephone numbers for these events, go towww.aspirebridge.organd select EVENTS.
http://www.asbi-assoc.org/index.cfm/grouting/traininghttp://www.asbi-assoc.org/index.cfm/grouting/traininghttp://www.asbi-assoc.org/index.cfm/grouting/traininghttp://www.asbi-assoc.org/index.cfm/grouting/traininghttp://www.asbi-assoc.org/index.cfm/grouting/traininghttp://www.asbi-assoc.org/index.cfm/grouting/traininghttp://www.asbi-assoc.org/index.cfm/grouting/traininghttp://www.asbi-assoc.org/index.cfm/grouting/traininghttp://post-tensioning.org/annual_conference.phphttp://post-tensioning.org/annual_conference.phphttp://post-tensioning.org/annual_conference.phphttp://post-tensioning.org/annual_conference.phphttp://post-tensioning.org/annual_conference.phphttp://post-tensioning.org/annual_conference.phphttp://post-tensioning.org/annual_conference.phphttp://www.concretesustainabilityconference.org/http://www.concretesustainabilityconference.org/http://www.concretesustainabilityconference.org/http://www.concretesustainabilityconference.org/http://www.concretesustainabilityconference.org/http://www.concretesustainabilityconference.org/http://www.concretesustainabilityconference.org/http://icaar2012.org/http://icaar2012.org/http://icaar2012.org/http://icaar2012.org/http://icaar2012.org/http://icaar2012.org/http://icaar2012.org/http://icaar2012.org/http://www.eswp.com/bridge/http://www.eswp.com/bridge/http://www.eswp.com/bridge/http://www.eswp.com/bridge/http://www.eswp.com/bridge/http://www.eswp.com/bridge/http://bridges.transportation.org/Pages/default.aspxhttp://bridges.transportation.org/Pages/default.aspxhttp://bridges.transportation.org/Pages/default.aspxhttp://bridges.transportation.org/Pages/default.aspxhttp://bridges.transportation.org/Pages/default.aspxhttp://bridges.transportation.org/Pages/default.aspxhttp://bridges.transportation.org/Pages/default.aspxhttp://www.cement.org/learn/professors_workshop.asphttp://www.cement.org/learn/professors_workshop.asphttp://www.cement.org/learn/professors_workshop.asphttp://www.cement.org/learn/professors_workshop.asphttp://www.cement.org/learn/professors_workshop.asphttp://www.cement.org/learn/professors_workshop.asphttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.post-tensioning.org/board_meetings.phphttp://www.post-tensioning.org/board_meetings.phphttp://www.post-tensioning.org/board_meetings.phphttp://www.post-tensioning.org/board_meetings.phphttp://www.post-tensioning.org/board_meetings.phphttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.asbi-assoc.org/index.cfm/events/eventshttp://www.asbi-assoc.org/index.cfm/events/eventshttp://www.asbi-assoc.org/index.cfm/events/eventshttp://www.asbi-assoc.org/index.cfm/events/eventshttp://www.asbi-assoc.org/index.cfm/events/eventshttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.worldofconcrete.com/http://www.worldofconcrete.com/http://www.worldofconcrete.com/http://www.worldofconcrete.com/http://www.worldofconcrete.com/http://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.aspirebridge.org/http://www.aspirebridge.org/http://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttps://netforum.pci.org/eweb/DynamicPage.aspx?Site=PCI_NF&WebKey=94c051b4-e413-4eff-952e-a94d3cc7f01fhttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.worldofconcrete.com/http://www.trb.org/Calendar/Blurbs/166565.aspxhttp://www.asbi-assoc.org/index.cfm/events/eventshttp://www.concrete.org/EVENTS/ev_upcoming_conventions.htmhttp://www.post-tensioning.org/board_meetings.phphttp://www.pci.org/cms/index.cfm/Callforpapershttp://www.cement.org/learn/professors_workshop.asphttp://bridges.transportation.org/Pages/default.aspxhttp://www.eswp.com/bridge/http://icaar2012.org/http://www.concretesustainabilityconference.org/http://post-tensioning.org/annual_conference.phphttp://www.asbi-assoc.org/index.cfm/grouting/training

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READER RESPONSE

Editor,I m a regul ar reader of AS PI RE

magazine and the AASHTO LRFD feature.I m fa sc in at ed by Dr. Me rt z th oroughknowledge and explanat ions of subj ectspertain ing to the code. I would like to aska ques ti on in regard to appl icab il it y ofcreep and shrinkage forces to be used in the

design of integral columns in multi-span,continuous concrete bridge structures. Whatis the best methodology to calculate the effectsof creep and shrinkage for substructurede si gn? The AASHTO LRFD Br idge DesignSpecifications includes CR and SH as partof all service and strength limit states (Table3.4.1-1), but no guideline is prov ided onhow to quanti fy these forces for des ign ofcolumns and other substructure elements.The concrete columns that are integrallyconnected to the superstructure will deformdu e to th e cree p an d sh ri nkag e of th e

superstructure. The LRFD Specifications doesnot address how to determine the columnmoments and shears resulting from creepand sh rinkage. Can you pl ea se answerthi s ques tion in your AASHTO LRFD page?Please feel free to email me if you have anyquestions.

Name and company withheldSan Francisco, Calif.

[Editors Note]We co mp le tel y agre e that Dr. Me r tz

knowledge of and ability to explain provisions

of the LRFD Specificationsis invigorating. Wecontinue to receive similar compliments abouthis articles and we appreciate his time andskills in contributing to ASPIRE. He carefullyconsidered this readers question and hasresponded in his column onpage 56.

Editor,Love the magazine! One sugges tion: In

some of the art icles (e.g., Texas Longes tBeams, page 29, Winter 2012), it s notclear exactly where the project is locatedbecause no mention is made of nearbycities. How about a small map for sucharticles?

Kathleen BergeronFederal Highway Administration

Washington, D.C.

[Editors Note]We like this suggest ion and apologize to

readers who may have been left wonderingabout the location of this or other suchprojects. In the future, we will more carefullydescribe locations or provide a locator map!

Editor,Our company was the general contractor

for the Mayor Mike Peters Bridge featured inyour Winter 2012 issue (pages 18-20). Wouldit be possible to have some additional copiesof the magazine sent to us? Wed like a fewcopies for us and will send some to a few ofour subcontractors.

Brendan ParkerLoureiro Contractors Inc.

Plainville, Conn.

[Editors Note]Happy to send them, Brendan. Nice project

in a tough location. The results speak forthemselves.

Editor,On behalf of myself and my co-authors, we

would like to thank you and the dedicatedteam at ASPIRE for your very nice job with

the Presidio Viaduct article (pages 30-33). Thearticle really looks good with the combinationof photos, rendering, and diagrams. Greatjob.

Ahmed M. M. IbrahimCalifornia Department of Transportation

Sacramento, Calif.

Editor,I must compl iment you on your

productions. I read almost every article andfind them to be well written and informative.I am happy that you were able to put together

this very useful magazine for the industry.A. Joseph SiccardiFIGG Bridge Engineers

Denver, Colo.

Editor,I am a long time reader of the ASPIRE

magazine and find it contains a lot ofinteresting and practical information.

Hong GuanCH2M HILL

Bellevue, Wash.

Editor,I receive and en joy ASPIR E. It is the

highlight of my work magazines.Andrew Howe

OBEC Consulting EngineersSalem, Ore.

Editor,ASPIREis a high quality publication

Kent BarnesMontana Department of Transportation

Helena, Mont.

Editor,I read with interest the ASPIRE article on

the Route 22 Bridge over the Kentucky River

near Gratz, Kentucky (Winter 2011 issue,pages 24-27). The measures taken to designand build the struc ture were inte resting. Iwa s eve n mo re in tr ig ue d when I wa sasked about the des ign and construc tionrequirements for a precast, spliced post-tensioned girder for a 500 ft. span. I returnedto the article on the Route 22 Bridge andread it again considering the possibilities.I was hoping that you may have prov idedsome of the design parameters or dimensionsof the girder. I looked at your website to seeif other girder dimensions or description of

construction equipment might be containedth ere somewhere, bu t found no fu rthe rinformation. While I am skeptical, I willat least look into the Route 22 Bridge andconsider if the 500 ft. span is possible or ifit is simply impractical. If you have any ofthat information or can point me in the rightdirection I would be grateful. That was a veryinteresting article. Keep up the good work!

Bruce KatesJacobs Engineering Group Inc.

St. Louis, Mo.

[Editors Note]We tr y to in cl ud e as mu ch te ch ni ca l

information in the articles as we can whilestaying within the space available and telling thestory about the bridge. You may be able to obtainmore information about the Route 22 Bridge bycontacting the author. NCHRP Report 517Extending Span Ranges of Precast PrestressedConcrete Girders is available to download at

www.trb.org/NCHRP/NCHRP.aspx and click onProject Reports under PUBLICATIONS on theleft side.
http://www.trb.org/NCHRP/NCHRP.aspxhttp://www.trb.org/NCHRP/NCHRP.aspxhttp://www.trb.org/NCHRP/NCHRP.aspx

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FOCUS

8|ASPIRE, Spring 2012

Corven Engineering has its mind setprimarily on one goal: providing clientswith the best possible, post-tensionedconcrete bridge engineering. We dothis by staying focused and maximizingpotential within our niche, saysfounder John Corven, president and

chief bridge engineer of the Tallahassee,Fla.-based company.

The firms expertise in concretesegmental and cable-stayed bridgesserves as its foundation. The companyleverages that expertise in four areasof work: new designs, constructione n g i n e e r i n g , i n s p e c t i o n a n drehabilitation, and developing andsharing technology. Work in theseareas mutually supports the others,solidifies the niche, and keeps us current

and relevant, he says.

This approach also provides many entrypoints for providing engineering servicesthroughout the life of a bridge. Welove to design new bridges and supportcontractors during construction,Corven adds, but it is just as importantto work with owners to extend bridgelife and increase operational capacity.

Corven Engineerings approach to workhas diversified its customer base. Thefirm opened its doors in 2000 workingprimarily for state departments oftransportation. The biggest change inour company has been the transition togaining more work with other types ofclients, he explains. The major part ofour business now comes from teamingwith contractors or larger engineeringfirms to provide our expertise on largeprojects.

An example is the companys work onPhase 1 of the Dulles Corridor MetrorailProject in Tysons Corner, Va. Corven is

working for Dulles Transit Partners, a

joint venture of Bechtel and WashingtonGroup, on this $1.8-billion project.Their work focuses on the design andconstruction support for more than5 miles of aerial guideways to carrythe extension of the WashingtonMetropolitan Area TransportationAuthority (WMATA) system. It includesfour types of precast concretesegmental bridge construction. (Formore on the project, see the Fall 2011issue ofASPIRE.)Mega-firms were needed for thatkind of project, Corven says. But weare able to help provide cost-effectivesolutions for specific bridge challenges.That help can involve a specific designfeature or the entire bridge design.

Post-Tensioned DesignsPost-tensioned concrete bridges, andsegmental bridges specifically, continueto offer great potential for newbridge designs, he notes. The basicprinciples of segmental construction aresound. It permits construction where

access is extremely difficult, especially

above traffic. It can help protect theenvironment, keep traffic moving,and provide complex geometry wherenecessary. It makes a very good choicein those circumstances.

Corven Engineering has worked withclients in a variety of delivery methods,although the designers favor the design-build approach, says Phil Hartsfield,vice president and head of constructionengineering. It allows us to be involvedfrom the beginning and follow theproject through to construction. Inmany cases, he explains, the companysentry point comes on the constructionengineering aspects, which brings themto the project after many decisions havebeen made that could have been mademore cost effective if made earlier.

If we are involved earlier, we can oftenspot problems that can be resolvedbefore they reach a critical point,he says. Design-build gives us thatearly input and lets us work throughchallenges that arise all the way through

the process.

Corven Engineeringstays true to its rootswhile leveraging its

expertise to maximizepotential

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The 790-ft-long Foothills Parkway Bridge No. 2 near

Wears Valley, Tenn., is a precast segmental concrete

bridge with span lengths up to 180 ft. Corven supplied

design and construction engineering services to Bell &

Associates Construction. Photo: Corven Engineering Inc.

The three-span Cross Street Bridge in Middlebury, Vt., was the first

bridge built in the state using the design-build delivery method. Corven

provided engineering for the spliced precast concrete girders. Photo:

Vanasse Hangen Brustlin Inc.

One such project is the Foothil lsParkway Bridge No. 2 now underconstruction in Blount County, Tenn.This balanced canti lever, precastsegmental bridge is being built around

a s teep, ruggedmountainside thatis environmentallyvery sensitive. Bella n d A s s o c i a t e sConstruction (primecon t rac to r ) , VSL(segment erection

and post-tensioning),a n d C o r v e n(engineer of recordand construct ione n g i n e e r )c o l l a b o r a t e d t odevelop a uniqueerection trestle andsegment walker forsegment erection.By working togetherearly, Corven wasable to design the

bridge with VSLserection equipmentin mind.

Another such projectwas the Cross StreetBridge in Middlebury,Vt., on which Corvenserved as the spliced-girder, main-spanengineer of record.The structure wasthe first project in

the state to usea d e s i g n - b u i l dformat. That deliverymethod produced a240-ft-long centerspan, the longestsimple-span, post-tensioned, spliced-

girder bridge in the United States.The three-span, 480-ft-long bridge isanchored by two precast, prestressedconcrete adjacent box-beam spanscrossing a local road and a railroad.

Environmental concerns led to thedesign, which eliminated a pier in OtterCreek. (For more on this project, see theWinter 2011 issue ofASPIRE.)

Owners are aware of the capabilitiesof these approaches and are using themmore often, says Hartsfield. Owners

are very intelligent and are embracingdifferent delivery methods. Sometimesthere are misconceptions that design-build approaches will eliminate everyissue early on, but theres still a lot ofwork to be done. But it does allow youto get the project into constructionquicker.

Owners are focusing on speed ofconstruction as a priority, notes Corven.There is a growing demand for fasterdelivery, as citizens want projects

completed, and they dont get cheaperdown the road. Precast concrete,including segmental construction,lends itself well to accelerating bridgeconstruction. We strongly supportthe federal governments Every DayCounts initiative.

Construction EngineeringT h e c o m p a n y a l s o p r o v i d e sconstruction engineering services toa growing number of contractors,adds Hartsfield. We are finding a lot

of success by supporting contractorsduring construction and ensuring thatdesigns are constructable.

An example can be seen in the workperformed on the I-95/I-295 NorthInterchange in Jacksonville, Fla. Theinterchange serves as a main accessroute and is the first major feature seenby tourists and visitors arriving from thenorth. The precast concrete segmentalalternative, built with the balanced-cantilever method, created a third-level

StayingFocusedby Craig A. Shutt

Segmental construction has proven to be an excellentsolution for the Dulles Corridor Metrorail Project, located in

the congested Washington, D.C., metroplex. Corven worked

with Dulles Transit Partners to design and construct the

aerial guideway, featuring more than 2700 precast concrete

segments. Photo: Dulles Transit Partners.

ASPIRE, Spring 2012 |9

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ramp with a horizontal curvature ofmore than 90 degrees and a radiusof 1250 ft. The thin, curving profileprovides a striking entry to the city. (Formore on this project, see the Winter2011 issue ofASPIRE.)

Another example currently underwayis the $350-million I-4/Lee Roy Selmon

Expressway Interchange in Tampa,Fla. The 12 elevated ramps provide avital transportation link in downtownTampa. There are more than 2500precast segments, consisting of morethan 1 million ft2 of precast concrete,being used. They are being built withboth the balanced-cantilever method,using deck-mounted mobile segmenterectors, and the span-by-span methodusing an overhead gantry.

Corven worked with PCL/ArcherWestern to improve the constructability,including introducing the deck-mountederectors. Of the 149 segmental spans,lengths range from 105 to 260 ft withradii as small as 590 ft and cross-slopesup to 10%.

Rehabilitation is GrowingPost-tensioning rehabilitation offers arapidly growing area of opportunity.We are working more and more onbridges in service, for which we performpost-tensioning inspections, evaluateproblems, and create a rehabilitationplan, Corven says. Its very interestingwork. In addition to the work plan, wehave had the opportunity to assist in theneeded repair work. Were not afraid toget our hands dirty.

An example is the work done on

four bridges in the Florida Keys: theChannel 5, Long Key, Niles Channel,and Seven Mile Bridges in MonroeCounty, Fla., for the Florida Departmentof Transportation (FDOT). The seriesof concrete segmental bridges, morethan 11 miles in length, required anin-depth post-tensioning inspectionthat led to Corven directing the repairoperation. The $11-million projectincluded inspection of external tendons,

The balanced-cantilever method was used to construct the I-95/I-295 North Interchange

Ramp in Jacksonville, Fla., for which Corven provided construction engineering services.The bridge features precast concrete segmental box girders in a 10-span continuous

configuration with a total length of 2256 ft. Photo: Superior Construction Company.

On the Florida Keys Segmental Bridges in Monroe County, Fla., Corven provided in-depth inspections and evaluations of the post-

tensioning system, and then performed the needed rehabilitation work. Photo: Corven Engineering Inc.

Corvens 12-Year History

Corven Engineering was formed in 2000after John Corven left DMJM to take ona project for the FDOT where severalpost-tensioned tendons had failed.That project began a 12-year history of

focusing on post-tensioned and cable-stayed bridges.

Corven began his career in 1979 at Figg& Muller Engineers, where he workedwith Philip Hartsfield on a variety ofprojects. Both men also worked fordifferent periods with Jean Muller in hisParis office. Hartsfield joined Corven in2006 from Parsons Corp., where hedbeen working since his previous firm,Finley McNary Engineers, had beenpurchased.

Among the projects undertaken by thecompany, in addition to those mentionedhere, are widening the Ramp A Bridge atthe I-75/SR 826 Interchange in Miami,the first such widening of a segmentalbridge in the United States, and therehabilitation of more than 70 milesof external post-tensioning tendons insegmental bridges in the Florida Keys.

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vibration testing, pour-back removals,and non-destructive inspections usingendoscopes.

It was a special project, in which wewere permitted to supplement our staffwith a contractor to do work together

in an Inspect/Maintain format Corvensays. There was no reason for us toinspect the bridges and prepare a setof plans, have FDOT take bids, andthen have a third entity inspect thecontractors work. We saved time andmoney.

With such work, the companys goal isto help achieve or extended a bridgesservice life. That will be the result nextsummer when work is completed on the943-ft-long Plymouth Avenue Bridge, asegmental concrete design that spansthe Mississippi River near Minneapolis.The 29-year-old bridge was the firstsegmental design built in the stateand, due to a drainage system failure,now needs its post-tensioning systemrepaired. The work will include thephased replacement of concrete whileinstalling new post-tensioning tendons.When complete, the bridge will returnto its original load-carrying capability,he says.

Such rehabilitations often are more

challenging than building from scratch,he notes. It takes time to discover theunique characteristics of the bridge andthe means and methods of how it wasbuilt, and then engineer a rehabilitationscheme within that framework. Its veryrewarding work but very difficult work.

Rehabi l i tation work offers greatpotential for the company, he says.Theres not enough money to fix allof our deficient bridges. Were justscratching the surface now. Our goal is

to work with owners to develop moreinnovative repair approaches that willlast longer and be more cost efficient.That will involve such techniques asusing supplemental post-tensioning andresupporting anchorage locations toprovide longer life.

Developing and SharingTechnologyDurability also has become a key focus,as owners look to cut maintenancecosts and extend service life. Corvens

expertise with evaluations of existing

bridges has led to a new facet ofits niche: production of manuals

for federal and state departments,especially related to durability. Theprocedural guides detail how to install,inspect, grout, and protect tendons toensure long life.

The company developed the 10-volumeNew Directions for Post-tensionedBridges in Florida for the FDOT, aswell as the Post-tensioning TendonInstallation and Grouting Manual forthe Federal Highway Administration( F H W A ) a n d L R F D c o n c r e t e

superstructure design courses forthe National Highway Institute. Themanuals are written by Corven andlong-time associate Alan Moreton. Thefirm is now writing a manual for thedesign of cast-in-place, post-tensionedconcrete bridges for the FHWA.

Creating design manuals along with itsother services keeps the firm busy. Weproduce a fair amount of work with asmall group of professionals, Corvensays of the companys 20 employees.

We pride ourselves on being able

to produce a large amount of qualityengineering product quickly, whether

its designs, inspection reports, ormanuals.

Most satisfying for Corven are repeatclients, We feel really blessed when aclient trusts us to work for them again.We dont take it for granted. It raisesthe bar for us to do even better thistime.

Repeat cl ients, coupled with thefirms versatility in growing niches,have it poised for more prosperity.

Infrastructure remains a big need,and even in tough economic times,were still moving forward on buildingbridges, Corven says. There aremany great opportunities for us tokeep doing what we do. The outlook isvery positive.

For additional photographs orinformation on this or other projects,visit www.aspirebridge.org and openCurrent Issue.

On the I-4/Lee Roy Selmon Expressway Interchange in Tampa, Fla., Corven is providing

construction engineering services to a joint venture of PCL Civil Constructors and

Archer Western Construction. The project includes more than 2500 precast segments

that vary in width from 30 to 60 ft. Photo: PCL Civil Constructors and Archer Western

Construction, joint venture.

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Government owns asset; private sector designs, builds and operates.

Cost and operational risks are transferred to private sector.

Private Sector

Owns-Operates

Design-Build

Finance-Operate-Maintain

Design-Build

Operate-Maintain

Design-Build

Government

Owns-Operates

Current P3 Model

Private

SectorRisks

Private Sector InvolvementCourtesyofTheCanadianC

ouncilforPublic-Private

Partnerships

PERSPECTIVE

Project delivery methods have been ina state of flux for many years in theUnited States. Legislation for public-private partnerships (P3s), and for otheralternative delivery systems, variesgreatly from state to state. However, thedemand for P3s is growing.

P3sA Natural ProgressionThe recent push for more P3s, and foralternative delivery models in general,

is due to the nations dire need to repairand upgrade existing infrastructure,and to do so quickly, with limitedpublic resources. The public sectorhas also begun to notice potentialbenefits of P3s, namely, the ability totransfer cost escalation risks, as well asthose associated with operations andmaintenance, to the private sector.

The Canadian Council for PublicPrivate Partnerships states that,. . . under the P3 approach, the public

sector contracts with a single entity. . . Under the traditional procurementapproach, the public sector mustcontract separately with each discipline.The efficiencies created through the P3approach can yield significant savingsfor the public sector, both through a

simplified management structure and bymitigating the risk of interface betweendisciplines.

The private sector demand for P3s isalso growing. Infrastructure providesdiversification benefits for investorsand is a solid investment over the longhaultransportation is a service thatthe public will always use.

P3s are not necessarily a new model,but rather the next level of risk transferto the private sector. Departments oftransportation used to construct theirown facilities. They soon figured outthat private contractors did a betterjob at managing ri sk for things likeequipment, labor productivity, unions,or even weather.

About 25 years ago, a trend to shiftdesign to the private sector began.At that point, the private sector was

handling design and construction underseparate contracts. A few years later,the notion of combining design andconstruction emerged as design-build,further reducing the public sectorsrisk of managing separate designersand constructors. Then, over the last

10 years in places like the UnitedKingdom, Australia, and Canada, camethe P3 contract, under which design,construction, and financingand inmost cases operations and maintenanceas wellare handled by the privatesector.

P3s Provide Risk TransferBenefits to the PublicSector

One of the main benefits of P3s forthe public sector, in addition toreduced construction, operations,and maintenance costs, is the abilityto transfer the risks that come withmanaging multiple contracts to theprivate sector. P3s also enable owners totransfer the risks associated with long-term, life-cycle performance, operations,and maintenance.

Tips for Designers andContractors

According to a recent P3 report byFMI, the industrys largest consulting,investment banking, and research firm,contractors should be very strategicabout selecting projects, build expertisethrough strategic ventures, understandthat concessionaires on these projects

by Matt Girard and Christie DeLuca, Flatiron Construction Corp.

A Contractors Point of ViewPublic-Private Partnerships:A Guide for Infrastructure Designers and Contractors

Degree of private sector risk & involvement.

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15/60ASPIRE, Spring 2012|13

usually require large financial backing,and start building relationships veryearly on.

Because P3s are large and complexprojects, designers and contractors needto be very careful to select the rightprojects. Flatiron bases decisions aboutwhich P3 projects to pursue on a fewkey factors. First, owners should shortlistthree or fewer teams. Second, ownersshould offer a stipend, typically around0.5 to 1% of the capital costs for theproject, and the contract terms must bereasonable.

Flatiron also wants to make sure theproject will actually get built. Wedont want to pursue projects that getcancelled during procurement, or worse,after the procurement is over andbefore award. Needless to say, Flatiron isextremely selective.

Flatiron also prefers to work withowners who have a past history with

P3s (or who have good advisors if they

have no history). We also prefer to workwith owners who have already resolvedthird-party issues, like right-of-way,permitting, and agreements with otherstakeholders like municipalities or utilitycompanies.

When forming partnerships, Flatironasks questions like: Who is an expertin this type of work? Who has workedwith this owner before? Who is in thearea? Who has the resources available?Partners with the lowest price are notnecessarily the best choice for a P3.

What a Good Design-BuildTeam Brings to a P3With so many factors and playersinvolved in a P3, one of our jobs asthe design-build contractor during aP3 pursuit is to help the financial andtechnical advisors feel confident aboutlending and investing money in theproject.

Lenders feel most comfortable with

people who have designed and built

P3 projects before and who understandthe risks. As a contractor, we helpcommunicate how this is a solidfinancial opportunity for them. If theyfeel confident we have covered all ourbases, in terms of risks, and have pricedthe project accordingly, the lenderstechnical advisors can write a goodreport.

This report affects the credit rating thatfinancial advisors place on the project.A better credit rating means lowerinterest rates on borrowed money,which in turn means lower repaymentcostsand the lowest payment typicallywins the job. Its like a mortgage. If ahomebuyer has a better credit rating,the banks mortgage rate will be lowerand the payments from the homebuyer, in this case the public sector, willbe lower.

The need for reliable infrastructurewill continue well into the future. P3s,with inherent advantages and risks,can at the very least provide a viablealternative for public owners to finance,build, and maintain infrastructureprojects. It is our job to help educateowners in the United States and bringour P3 experience from places likeCanada in hopes that together we canmeet the growing demand for safe andreliable infrastructure.

For additional information on P3s,visit The Canadian Council forPublic-Private Partnerships websiteat www.pppcouncil.ca.

As part of a larger P3 consortium, Flatiron led the design-build team on the Northeast

Anthony Henday project, a new 13-mile (21-km) portion of a ring road around Edmonton,

Alberta, Canada. The owner, Alberta Transportation was able to complete this more than

$1 billion project significantly faster and arguably less expensively by letting it as a single P3

project, rather than multiple low-bid contracts.

Flatiron constructed approximately 3 miles

of four-lane highway through Kicking Horse

Canyon on the border between British

Columbia and Alberta, Canada. It included

a 1328-ft-long bridge nearly 300 ft above

the river.
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The Commonwealth of Virginia wasfounded in the seventeenth century asa risky, but ultimately highly successfulbusiness venture. Today, Virginiacontinues to focus on creating aninviting business environment thatpromotes competition, encouragesprivate investment, and invites theprivate sector to identify and developinnovative solutions to enhance itsinfrastructure.

As with any successful business venture,Virginia must remain focused anddiligent about creating an attractivebusiness environment. Virginia mustcontinue searching for solutions toattract private investment. A significantaspect of that effort is maintaining atransportation network that allows forefficient freight movement, access toits ports, and interstate movement ofgoods and services.

Since Virginias enabling legislation

for public-private partnerships (P3)was enacted by its General Assemblyin 1995, Virginia has advanced nearly$5 .0 b i l l i on wor th o f P3 fo rtransportation infrastructure eitherconstructed, under construction, orunder agreement.

Reinventing the P3ProgramIn 2010, the governor initiated a fullassessment of Virginias P3 programin an effort to reinvigorate the

development and completion of P3projects. The results of the assessmentwere as follows: The program was limited in focus

to development of highways. Ownership rested with multiple

staff. The program was reactive and was

constrained by a lack of funding forproject development.

In response to the assessment,the Secretary of Transportation, inDecember 2010, introduced a manualtitled, Public-Private Transportation ActImplementation Manual and Guidelines.The manual provides a project deliveryframework for the development andimplementation of both solicited andunsolicited P3 projects that proactivelyidentifies, develops, and delivers theCommonwealths priority transportationprojects in a consistent, transparent,timely, and cost-effective manner. Theresult of this action means Virginiasapproach to its P3 program is now aprogram-based perspective ratherthan a project-by-project response.Key to the program-based approach isdevelopment of a multimodal pipelineof candidate P3 projects.

In addition to the process reviewsand improvements in the manual, anOffice of Transportation Public PrivatePartnerships (OTP3) was created to

focus specific financial and humanresources on the ident i f icat ion,development, and delivery of P3s acrossall modes of transportation, including

rail, transit, marine, aviation, androadway projects. In 2011, the directorof OTP3 was charged with creatingan environment that encouragesprivate investment and proactivelyidentifies, assesses, and delivers theCommonwealths priority transportationprojects. Furthermore, the internalstructure of the OTP3 utilizes resourceswith diverse backgrounds in finance,law, project development, engineering,and operations along with legal,financial, risk, and business consultantsthat augment the internal staffingresources.

Learning from the PastVirginias leaders have taken tangiblesteps forward to implement a P3program that has learned from its pastexperiences. In addition to the creationof the OTP3 and the restructuring of themanual, Virginia has learned from itsexperience in the areas of risk assessmentand project development.

Risk analysis and management is anessential part of the development of anyproject, whether it is procured following

by Dusty Holcombe, Virginias Office of Transportation Public-Private Partnerships

Construction of Pocahontas Parkway.

All photos: Virginia Department of

Transportation.

PerspectiveAn Owners ViewpointVirginias Public-Private Partnership Program is Open for Business

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a more traditional delivery method,design-bid-build or design-build, or asa P3. The assessment of risk, especiallyon a complex transportation project,must be conducted throughout the lifeof a project to assist in determining ifthe continued development of theproject brings a value to the owner orthe private sector investor. For Virginiastransportation agencies, the OTP3has developed a guidance documentthat can be utilized to increase theeffectiveness of risk analysis andmanagement. It is available at www.

vappta.org/publ icat ions.asp. Thedocument includes processes thatfacilitate the agencys: identification and understanding of

a projects risks, identification strategies to mitigate

the likelihood of and impact of riskelements,

allocation of risk to the party bestable to manage the impact, and

preparation of an adequatecontingency to cover both knownand unknown risks.

Lessons in project development have alsobeen implemented including completionof value for money analysis guidanceand increasing the transparency ofthe program. When the OTP3 openedin December 2010, its first objectivewas the creation of a website (www.vappta.org/) that provides accurate andupdated information on each of thestages of project development and ondocuments created to assess, develop,and execute comprehensive agreements

for P3 projects. The website provided

background in the structure of theoffice, information about projects at alllevels of development, documentationdeveloped for use by the OTP3 andVirginias transportation agencies, andthe latest news about existing andpotential P3 projects. Additionally,the OTP3 codified a Value for Moneyguidance document. This will be usedby the OTP3, in coordination with thetransportation agency, several timesthroughout the project developmentprocess to assess whether the currentstructure of the project and the bid that

has been presented by the private sectorbring value to Virginia. It will also allowthe OTP3 to assess and recommend adevelopment structure, such as a tolledconcession, availability payment, or amore traditional structure, which deliversthe optimal structure of net life-cyclecost, quality development, and valuefor the investment provided by theCommonwealth.

Looking to the FutureThe development and sustainability of

an adequate infrastructure network hasbecome increasingly more expensive,making innovative financing and deliverymethods a critical tool to maintaining thehealth of Virginias economy. In 2011,the governor introduced legislationthat provided the largest investment intransportation in Virginia in more thana generationover $4 billion additionalfunding for infrastructure improvementpro jects . Moreover , a V i rg in iaTransportation Infrastructure Bank(VTIB) was created to provide another

innovative financing tool for construction

and capital maintenance for Virginiastransportation infrastructure needs.Funding capitalized within the VTIB willprovide low interest loans with maturitydates of 20 to 30 years. These fundswill be made available to governmententities, railroads, transit companies,and private sector companies for the

initiation and development of criticaltransportation projects.

In this era of fiscal responsibility, the P3delivery method offers an importanttool for development, construction,and operations of transportationinfrastructure by leveraging investmentsand partnering with the private sector. Inother words, Virginia and its P3 Programare open for business.

I-495 Capital Beltway Express Lanes connection to I-395.

Metrorail construction at Tysons Corner, Va.

I-495 Capital Beltway Express Lanes

construction.

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Ample new

access provided

for pedestrians,

snowmobiles, cars,

and the Zumbro

RiverZumbrota, Minn., is the quintessentialquiet l ittle town, tucked into thesoutheastern corner of the statebetween Minneapolis/St. Paul andRochester. While it may be small,the town relies on its transportationinf ras t ructure as much as anylarge metropol itan area. And amajor component of Zumbrotastransportation system is the bridge thatcarries Minnesota Trunk Highway 58(T.H. 58) over the North Fork of theZumbro River. With a 23-mile detourto the nearest alternative trunkhighway river crossing, a closure of the

T.H. 58 bridge would affect a variety oftransportation users including residentsgoing about their daily business,school buses, farm-to-market truckers,and commuters to the towns largerneighbors. Along with its functionalimportance, the crossing also hashistorical and social significance to thelocal community.

The T.H. 58 crossing was closed,

however, in 2010 while the MinnesotaDepa r tment o f T ranspo r ta t i on(MnDOT) had a replacement bridgebuilt. The new bridge, Bridge 25025,was necessary for the usual reasons.Its predecessor, Bridge 5188, was bothfunctionally obsolete and structurallydef ic ient. The steel beams andconcrete deck had suffered significantdeterioration, its sufficiency ratinghad dropped to 18.4 (on a 100-pointscale), and its inventory rating wasonly HS-11 (for comparison, new

bridges in Minnesota are designed forapproximately HS-25). This was not aroutine bridge replacement project,however. Several challenges had to be

overcome, and a variety of design andcommunity issues had to be addressedby the project team.

Local Meaning of BridgeThe existing bridge, Bridge 5188, didnot have an official historic designation.However, the bridge site had majorhistoric significance because of thepredecessor to Bridge 5188. When itwas built in 1932, Bridge 5188 replaced

a covered bridge that had been builtin 1869. Instead of being demolished,the covered bridge was removedintact and stored for many years. Itwas refurbished in the 1990s, and in1997 it was once again erected overthe Zumbro River at a trail crossingapproximately 300 ft upstream. TheZumbrota Covered Bridge is the onlyhistoric covered bridge in Minnesotaand is a source of great pride for theZumbrota community.

The Covered Bridges replacement alsohad special meaning for the community,especially the areas military veterans.Bridge 5188 had a plaque on its

profile VETERANS MEMORIAL BRIDGE (BRIDGE NO. 25025)/ ZUMBROTA, MINNESOTABRIDGE DESIGN ENGINEER:Minnesota Department of Transportation, Oakdale, Minn.

ROADWAY AND PRELIMINARY BRIDGE DESIGN ENGINEER:Yaggy-Colby Associates, Rochester, Minn.

PRIME CONTRACTOR:Minnowa Construction, Harmony, Minn.

PRECASTER:Cretex Concrete Products, Maple Grove, Minn., a PCI-certified producer

AWARDS:2011 PCI Bridge Design Awards, Best Bridge with Main Spans up to 75 ft

by Todd R. Stevens, Minnesota Department of Transportation

Zumbrota Veterans Memorial Bridge

View of Veterans Memorial Bridge showing bench provided for a future trail. Photo: MnDOT.


PROJECT

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southwest corner post dedicated tothe areas fallen military veterans. Thebridge served as an unofficial veteransmemorial, a distinction made morespecial by the local VFW Post locatedjust off the bridges southeast corner.Project plans and special provisionscalled for the plaque to be salvaged

during bridge removal, and reset intothe southwest corner post of the newbridge. The new bridge was fittinglyrenamed the Veterans MemorialBridge by proclamation of the mayorat the projects ribbon cutting. Otherfeatures from Bridge 5188 were alsoreplicated in the new bridge, includingthe ornamental metal rail ing andconcrete rail posts, which were stylisticrepresentations of the Covered Bridge.

While not officially historic, Bridge 5188turned out to have more historicalsignificance than people realized.During demolition, a time capsulewas discovered within the concretebehind the veterans plaque. The timecapsule contained many fascinatingartifacts from the time of the 1932construction, including a page from thelocal newspaper, an American Legionroster, and a listing of local soldiers whohad fought in conflicts dating backas far as the Civil War. All items weregiven to the Zumbrota Area HistoricalSociety. A new time capsule, containing

similar items, was placed in the samelocation in Bridge 25025. Much of thetime capsule information was in current

electronic formats, along with writteninstructions to guide a future generationon how to access the information.

Hydraulics and NewStructureBecause of funding realities, MnDOTshydraulic design guidelines, and thelimitations inherent to the site, it wasdetermined that hydraulic improvementswere not possible. Consequently, thehydraulic focus shifted to alternativesthat would avoid negative upstreamimpacts, particularly to the CoveredBridge. The final recommendation was atwo-span bridge utilizing the Minnesota27M beam, a 27-in.-deep precast,prestressed concrete bulb tee. It wasthe most practical combination of beamspacing and span length. The resulting144-ft-long bridge is 34 ft longer thanthe bridge it replaced and providesnearly 25% more waterway opening

for the 100-year flow. It moves the pierfrom the middle of the stream to theedge of the low-flow channel.

The pier columns are 4 by 8 ft with1-in. chamfers on the corners. Thepier cap is 4 ft 4 in. wide and 5 ftdeep over the columns tapering to4 ft deep between each column.The bridges two equal, simple-spanlengths are 72 ft. The concrete deck iscontinuous over the joint but there isno continuity diaphragm around thebeams. This is standard practice withprecast, prestressed concrete beams inMinnesota. The beams are spaced at6 ft 5 in. for a total width of68 ft 6 in. The bridge provides two12-ft-wide travel lanes, two 14-ft-wideshoulders, and 6-ft- and 8-ft-widesidewalks.

The specified compressive strengthof the beam concrete was 8000 psi.Additional durability features includeepoxy-coated reinforcement andthe addition of a low-slump concrete

wearing course over the 7-in.-thick cast-in-place structural deck.

The erection of beams in one spanwas accomplished by a single cranepositioned on the earthen bench nearmidspan that will become a future trail.A launching beam was used for theerection of the beams in the span overthe river, allowing the contractor to usetwo smaller cranes. With the launchingbeam, one end of the beam was lifted

TWO-SPAN, PRECAST, PRESTRESSED CONCRETE BEAM BRIDGE WITH SEMI-INTEGRAL ABUTMENTS, CAST-IN-PLACE CONCRETE COMPOSITE DECK, AND CAST-IN-PLACE CONCRETE ABUTMENTS AND PIERS / MINNESOTADEPARTMENT OF TRANSPORTATION, OWNER

BRIDGE DESCRIPTION: 144-ft-long, 68.5-ft-wide, two-span precast, prestressed concrete beam bridge providing sidewalk and trail over a river

STRUCTURAL COMPONENTS:27-in.-deep precast, prestressed concrete bulb tees, cast-in-place composite concrete deck, drilled shaft piers, cast-in-place concrete piers, and semi-integral abutments

BRIDGE CONSTRUCTION COST:$111/ft2

The original Zumbrota Covered Bridge was built in 1869, removed in 1932, refurbished,

and returned to service as a trail bridge in 1997. Photo: MnDOT.

The Zumbro River shown at flood stage

on September 23, 2010, toward the

conclusion of construction. Photo: City of

Zumbrota.


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The first beam has been placed in the Veterans Memorial Bridge in Zumbrota, Minn.

The launching beam is seen in the background and is used to slide the concrete beams

across the river where they could be lifted by a crane located there. Photo: MnDOT.

from the transport truck and placedon a roller support on the near end ofthe launching beam. That end of thebeam is pushed across the span, withthe other end supported by a crane.Once across, the girder was set into itsfinal position with cranes at both ends.This operation was simplified on thisbridge by the presence of the earthenbench under the north span. The useof launching beams is fairly common inMinnesota.

FoundationsLike the existing bridge, the southabutment is founded on a spreadfooting on rock at an elevationapproximately 3 ft below streambed.The abutment is tall, with the southeastwingwall carved into the existing rockface. The north abutment, located

within the roadway embankment,is approximately 60 ft from the low-flow channel, where the top ofbedrock had dropped to roughly 30ft below streambed. Consequently,the recommendation for the northabutment was a short stub abutment

on steel H-piles. Both abutmentsutilized MnDOTs semi-integral details,eliminating the need for expansionjoints in the superstructure.

At the pier, hydraulic modeling indicated23 ft of potential scour and drilledshafts were used for the foundations,with a 48-in.-diameter rock socketapproximately 15 ft into the dolostonebedrock and a 54-in.-diameter shaftfrom the top of the rock socket up tostreambed. Since three shafts couldprovide the necessary support, a singleshaft was positioned beneath each ofthe three pier columns.

ScheduleThe contract limited roadway closure toa 14-week period beginning the secondweek of June and ending before the

Labor Day weekend in September. Inthe end, the contractor was not able tomeet the Labor Day completion date,and completion was further delayedby unusually wet weather and historicflooding during September. The centertravel lanes of the bridge were opened

to traffic at a ribbon cutting ceremonyon September 17, minimizing theinconvenience to local travelers. Minorwork continued on the sidewalks andrailings with all work completed by theend of September 2010.

The Final ProductThe construction of Bridge 25025 wasa success in many ways. It replaceda severely deteriorated bridge with acost-effective and durable concretestructure. The 27-in.-deep Minnesota

27M bulb tee allowed for the hydraulicopening to be optimized. Additionalwidth provided by the new bridge crosssection will accommodate all modes oftransportation, including snowmobilesin the winter. The lengthened bridgeprovides space on the river bank underthe north span for a trail underpass,which will be connected to the regionaltrail system in the future. And, thenew bridge was designed and built ina manner that emphasized the localcommunitys focus on the sites bridge

history, as well as the sacrifices made bythe areas military veterans.__________

Todd R. Stevens is principal engineer

at the Minnesota Department of

Transportation in Oakdale, Minn.

For additional photographs orinformation on this or other projects,visit www.aspirebridge.org and openCurrent Issue.

Northwest corner showing aesthetics,

including railing post and insets

replicating the covered bridge. Photo:

MnDOT.

Looking upstream at the river pier. Photo: MnDOT.


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http://www.epoxyinterestgroup.org/http://www.bentley.com/ASPIRE

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Eugene, Ore., is one of the leadingregional areas for non-motorizedcommuting. A bicycle- and pedestrian-friendly transportation system is a wayof life in this medium-sized universitytown located at the south end of theWillamette Valley. Not surprisingly,

the residents of Eugene considernatural space very important and seekenvironmentally friendly solutions toproblems.

As a result, the city of Eugene boastsan extensive path network. The city,bisected by the Willamette River anda four-lane highway, has promotedbicycle and pedestrian commuting bybuilding paths near the river, connectedby a series of bridges at strategicpoints. In north Eugene, Delta Highwayruns roughly parallel to the east bankof the river. Historically, bicycle and

pedestrian traffic for this 2-mile-longstretch was restricted to crossing thehighway at two busy interchanges.

The Delta Ponds Pedestrian Bridge,const ructed in 2010, prov idesa key connect ion between the

neighborhoods east of Delta Highwayand the popular riverbank path systemto the west of the highway. The bridgeskirts the south edge of the DeltaPonds city park and natural area, abackwater pond system hydraulicallyconnected to the Willamette River. Thesweeping structure not only providesa much-needed safe crossing of thehighway for bicycle and pedestriantraffic that is compliant with theAmericans with Disabilities Act (ADA),it also offers a very popular andpleasant vantage point for viewing thesurrounding ponds.

Structural FormThe primary feature crossed by theDelta Ponds Pedestrian Bridge is DeltaHighway. The bridge also crosses aslough immediately west of the highwayand skirts one of the larger ponds inthe Delta Ponds system. Keeping a

light footprint on the ground dictateda bridge with a total length of 760 ftand out-to-out width of 18 ft 11 in. Thewidth inside handrails is 14 ft.

Because it crosses the highway, thebridge occupies a visually prominentposition in the landscape. Trees in thearea are seldom taller than 50 ft, andbuildings are no taller than two stories,so a properly proportioned structurewould blend into this surroundingrather than overpower it. Spans had tobe short, allowing slim columns and ashallow deck.

profileDELTA PONDS PEDESTRIAN BRIDGE/ EUGENE, OREGON

BRIDGE DESIGN ENGINEER:OBEC Consulting Engineers, Eugene, Ore.

CONSULTING ENGINEER:Jiri Strasky, Greenbrae, Calif.

PRIME CONTRACTOR:Mowat Construction, Clackamas, Ore.

PRECASTER:Knife River Prestress, Harrisburg, Ore., a PCI-certified producer

CONCRETE SUPPLIER:Eugene Sand and Gravel, Eugene, Ore.

POST-TENSIONING CONTRACTOR:DYWIDAG-Systems International USA, Long Beach, Calif.

by Andrew Howe, OBEC Consulting Engineers

Delta Ponds Pedestrian BridgeExtending a Sustainable Transportation Network

The Delta Ponds Pedestrian Bridge provides a

safe crossing over a busy highway. All photos anddrawings: OBEC Consulting Engineers.


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The bridge occupies a visually prominentposition in the landscape.

Traffic clearances over Delta Highwaydictated the bridge soffit elevation,and the short distance between DeltaHighway and the required easternpath terminus became a significantissue during design. Because 1 ft ofstructure depth would add 20 ft ofpath length (using a 5% maximumgrade), minimizing depth from soffit to

finished path elevation was an absolutemust if the bridge was to fit within theconstrained site.

Keeping bridge foundations outsideof sensitive natural areas meant thatcrossing the slough was a significantconstraint to address. While the spanover Delta Highway was 170 ft, thespan over the slough was only slightlyshorter at 120 ft. The required spanlengths contradicted the use of ashallow, slender structureunless a

somewhat unconventional design wasused.

The design team proposed a single-tower cable-stayed bridge, and the cityselected it as the preferred structuretype. The main cable-supportedspan was 170 ft with back spans of120 ft (over the slough) and 50 ft. Aseries of thirteen 30-ft-long cast-in-place concrete slab spans at the westapproach and a single 30-ft-longapproach span at the east approach

comprise the balance of the bridgeslength.

Small FootprintThe alignment of the bridge along thesouth side of the ponds had been usedbefore. A 78-in.-diameter sanitary sewerline was previously constructed betweenthe ponds and the adjacent developedproperty. This required the bridge tohave a small footprint, meaning the useof spread footings or a pile group wasnot feasible. The solution was to usesmall-diameter drilled shaft foundations.Bedrock in the area is relatively shallow

and light loads meant that drilled shaftswouldnt normally be longer than 30 ft.

Four-ft-diameter drilled shafts wereselected and installed within 10 ft of thesanitary sewer. A cast-in-place concretecolumn sits on each drilled shaft. Thereare 15 columns with a 2-ft 7-in.-squarecross section and 4-in. chamfers at eachcorner. The tallest column is 33.5 ftlong.

Precast V Pylon TowerOne of the immediately noticeableelements of the Delta Ponds PedestrianBridge is its innovative twin-leg,V-shaped pylon, evoking an upside-down delta shapethe mathematicalsymbol typical ly used to denotechange. The V shape was dictatedby underground constraints becausethe 78-in.-diameter sanitary sewerturns to run parallel to Delta Highway,

ASYMMETRIC, THREE-SPAN, CABLE-STAYED CONCRETE BRIDGE WITH 14 APPROACH SPANS OF CAST-IN-PLACECONCRETE SLAB / CITY OF EUGENE, OREGON, OWNER

BRIDGE DESCRIPTION:A 760-ft-long concrete bridge featuring a 340-ft-long, asymmetric, three-span cable stayed section with fanned stays. The170-ft-long main span uses partial-depth precast concrete deck panels with cast-in-place composite topping having a combined maximum thickness of 1ft 2 in., which is post-tensioned together with adjacent, cast-in-pace concrete spans.

STRUCTURAL COMPONENTS:15 precast concrete deck panels, 10 ft long and 18 ft 11 in. wide; precast pylon legs, 86 ft long and 4 ft 0 in. by2 ft 5 in.; 14 cast-in-place concrete approach slabs 30 ft long; fifteen 4-ft-diameter concrete drilled shafts support 2-ft 7-in.-square pier columns; one8-ft-diameter shaft supports the pylon.

BRIDGE CONSTRUCTION COST:$3.9 millionAWARDS:2011 Federal Highway Administration Environmental Excellence Award; 2011 American Council of Engineering Companies, OregonEngineering Excellence Honor Award

Because the site is surrounding by short buildings and trees, the design team sought to

blend the 760-ft-long Delta Ponds Pedestrian Bridge into its surroundings as much as

possible.

The Delta Ponds Pedestrian Bridge looking over Delta Ponds. Red LED lighting along the

deck edge and the top stay create a stunning effect at night.


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deck (symm. about)CL

7 1 1 9 7

CIP deck overprecast panel 925/8 dia. metallic

P.T. duct, typ.

Precastpanels,

typ.

11

5

44

2 86 4

9 5

crossing under the bridge and limitingfoundation options. Additionally, anexisting storm water system crossesunder the highway immediate lyadjacent to the pylon.

The presence of these elementsconfirmed the tower would require asmall footprint. A pylon leg angle ofjust less than 8 degrees from vert icalaccomplished this goal, shavingmore than 6 ft from the width of thefoundation and allowing the use of a

single, 8-ft-diameter drilled shaft.

Inconveniently, the pylon had to belocated between a busy highway anda slough. Fabricating the pylon legs onsite didnt seem manageable, given thelimited staging area. The design teamspecified the use of precast concretepylon legs. The pylon legs connect tothe foundation using plates weldedto steel anchors and connect to thedeck using threaded inserts to attachreinforcement.

The length of each pylon leg is 86 ft. Itscross section is an irregular shape withoutside plan dimensions of 4 ft 0 in. by2 ft 5 in. for almost the full length.The leg tapers to a 4-ft-long knife edgein its upper 3 ft. The use of a precastconcrete pylon had several advantages.Tighter controls on concrete mix design,concrete placement, and curing allowedthe use of higher-strength concrete inthe pylon legs. The specified concretecompressive strength was 6000 psi.

Precasting meant higher confidence

for concrete consolidation in thecongested areas at the stay connections,deck connections, and tower base. Toenhance the strength of the pylon legswithout increasing their dimensions,two 13/8-in.-diameter, ASTM A722post-tensioning bars extended fromthe base of the legs approximately 60ft to almost the stay anchorages. Thebars were tensioned in the precastfabrication plant to a total force per legof 332 kips.

Over TrafficMuch of the Delta Ponds PedestrianBridge could be constructed onfalsework, but this wasnt an optionover Delta Highway because of thehighways heavy traffic. Bui ldingon previous experience on similarbridges (see ASPIRE Fall 2010), aconstruction sequence was developed

that cantilevered precast concrete deckpanels over the highway. This sequenceeliminated the need for daytime laneclosures on Delta Highway, minimizingimpacts to public traffic.

The back spans and 10 ft of the main

span were constructed on falseworkin advance of construction overDelta Highway. Precast panels wereplaced during lane closures at night.The stays were then connected andadjusted during the day. The 15 deckpanels were partial depth to limit thehandling weight and allow for a cast-in-place topping that provides a smoothriding surface. Precast deck panelswere 10 ft long, 18 ft 11 in. wide, and1 ft 7 in. thick at the curbs. Thespecified concrete compressive strengthwas 6000 psi.

As deck construction advanced, deckgrades and stay stresses were checkedregularly. Forces in the stays were small,and a simple hydraulic jack systemallowed for unloading the lower portionof a stay so that a coupling nut could beturned to adjust the stay length.

Topping It OffThe cast-in-place concrete toppingcompressive strength was specifiedto be 5000 psi, the same as the cast-

in-place spans. The topping containsa longitudinal post-tensioning systemto control stresses in the deck paneljoints. The panel joints are designed asthey would be in a precast segmentalstructure, with zero tension underdesign serv ice loads. This post-tensioning extends just over half thetotal bridge length, terminating

The structures concrete V-shaped pylon tower is an impressive sight for bikers and

pedestrians as they cross the Delta Ponds Pedestrian Bridge.

Half section of the precast deck panel with cast-in-place topping slab and post-

tensioning shown. The deck cross-sectional dimensions were constant throughout the

bridge.


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at a deck joint in span 11. The post-tensioning consisted of nine tendonseach with seven 0.6-in.-diameter strandsevenly distributed across the deck.

Finishing TouchesLate in the project development, the cityof Eugene secured additional fundingthrough the American Reinvestmentand Recovery Act (ARRA), which ledto the installation of energy-efficientLED luminaires to replace the plannedincandescent bulbs.

In addition to the energy-efficient

luminaires, the ARRA funds allowed

add i t i ona l ae s the t i ctouches to be added,including red LED ropelights on the deck edgeand top stay of the mainspans that make thebridge a strong visual

exper ience day andnight, pushing the bridgetoward landmark statuswithin the community.

In November 2010, theDelta Ponds PedestrianBridge opened for use.Long awaited by thepublic, the bridge wasinstantly appreciated forits graceful form and

has become a beacon for bicyclistsand pedestrians, adding to Eugenesreputat ion for accommodat ingenvironmentally friendly commutingoptions.

__________

Andrew Howe is senior project engineer

with OBEC Consulting Engineers in Salem,

Ore.

For additional photographs orinformation on this or other projects,visit www.aspirebridge.org and open

Current Issue.

Section through a pylon leg between the bottom and

the first stay anchor.

Placing the main span topping slab on

the precast panels. The longitudinal post-

tensioning ducts can be seen betweenthe curbs of the precast panels.

Daytime closures on Delta Highway were

out of the question, so crews erected the

precast concrete pylon tower and placed

the precast deck panels at night.

A E S T H E T I C SCOMMENTARY by Frederick Gottemoeller

This bridge is an excellent example of how a community can get more use out of a favored and well-loved park. The align-ment itself reminds one of a stroll through the woods. It curves around obstacles and over conflicting uses like a meander-ing park walkway, but in the air.

On its way it creates a dramatic landmark for the community and the park. The tower and cable planes impose an easily

understood geometric silhouette on the sky. The towers arms are simple, thin rectangular prisms. The angle of the towersarms is well chosen. The tower recalls the triumphant Touchdown gesture well known in football. Bracing of the armsat their base is achieved not by thickening the arms, but by thin triangular walls, leaving a V-shaped slot that preserves the

view through the tower. The arms end equally well, with a simple diagonal slice.

The semi-harp stay pattern is also well chosen. The stays create a fascinating moir pattern of interacting lines that shift and change as driv-ers move under the bridge. The red color brings out the pattern on both sunny and cloudy days. The lighting of the upper stay preserves thebridges memorable image at night.

Finally, the short spans on the approach allow the thin deck of the cable-supported span to continue unchanged to the abutment, giving thewhole structure a unified appearance. Short spans allow thin columns. Even though there are many of them, their thinness and their simpleshape means that the views through the bridge are not significantly interrupted. Designers often assume that long spans are better for ap-pearance. That is true in many cases, but this is not one of them. Plus, the economy of the short spans has allowed the community to obtain asignature bridge at a remarkably low price.


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The I-405 Renton, Wash., Stage 2 design-build project provides improvements toaccommodate high occupancy vehiclesand new freeway connections to localarterials of the city of Renton. As partof this project, the existing 1970svintage Benson Road Bridge over I-405was replaced with a new, wider, longerbridge that enabled widening of thefreeway below. The project was partof the Washington State Departmentof Transportations (WSDOTs) I-405Corridor Improvements Program.

Superstructure DescriptionThe replacement bridge provides fortwo traffic lanes, two bicycle lanes,and one sidewalk for a curb-to-curbwidth of 40 ft. The bridge consists ofa three-span structure with spans of132, 207, and 182 ft. The bridge wasconstructed with spliced precast, post-tensioned concrete girder technology.

Span 1 used single segment precastgirders and Spans 2 and 3 used two-segment precast girders.

Four girder l ines were used, withthe multi-segment spans erectedon temporary falsework bents. Thefield-cast girder and pier closurep l a c e m e n t s we r e c o n s t r u c t e dmonol i th i ca l l y wi th the br idgedeck placement. The bridge wasthen post-tensioned, followed byplacement of the abutment enddiaphragms. The girders were thenjacked up at the abutments to re-setthe elastomeric bearings to relieveshort-term deformations causedby post-tensioning. The final resultwas a highly efficient, cost-effective,durable, fully composite structure. Thebridge construction was completedahead of schedule and was opened totraffic in July, 2010.

Options ConsideredThe replacement for the existing BensonRoad Bridge was conceptualized as afive-span curved steel plate girder bridgein the original request for proposal (RFP)documents. At 845 ft long, the RFPdesign represented a significant portionof the total project construction cost.The long lead time for the procurementof steel also posed a significantscheduling risk to the overall project.

During the proposal stage, thedesign-build team considered variousalternatives. Most significant waschanging the overcrossing alignmentand the use of different structuretypes and materials. The final solutionselected was a three-span alternativethat would significantly shorten theoverall bridge length to approximately521 ft. The revised alignment alsoallowed the bridge structure to be

profile BENSON ROAD BRIDGE/ RENTON, WASHINGTONBRIDGE DESIGN ENGINEER:CH2M HILL, Bellevue, Wash.

PRIME CONTRACTOR:I-405 Corridor Design Builders (a joint venture between CH2M HILL and Gary MerlinoConstruction Co.), Renton, Wash.

BRIDGE SPECIALITY CONTRACTOR:Mowat Construction Company, Woodinville, Wash.

PRECASTER:Concrete Technology Corporation, Tacoma, Wash., a PCI-certified producer

POST-TENSIONING CONTRACTOR:VSL, Wheat Ridge, Colo.

by Paul Guenther, Ben C. Gerwick Inc. and Hong Guan, CH2M HILL

THE BENSON ROAD BRIDGE OVER I-405Extenin Peca Concte Span ith Wsingto Sate S Gir

The Benson Road Bridge over I-405 in Renton, Wash., has spans of 132, 207, and 182 ft and at a 45-degree skew.

All photos: CH2M HILL.


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The final solution would significantly shortenthe overall bridge length.

placed along a tangent alignment,thus making a precast concrete optionmore feasible. The revision required anadditional off-ramp flyover bridge overBenson Road that was also a precast

concrete structure. It was needed toaccommodate the new roadwayalignment, but the reduction in totaldeck area and the change from steelto precast concrete reduced the totalbridge cost by over $700,000. The useof concrete in lieu of steel also reducedfuture maintenance requirements andwas perceived as an advantage by theowner.

Design ConstraintsLocated in an urban environment, theproject site is geometrically constrained.The owners requirement to maintainall lanes of traffic on Benson Roadand the I-405 freeway below duringcons t ruc t i on added add i t i ona lconstraints. To avoid excessively longspans, one of the center piers (Pier 3)needed to be located in the median ofmainline I-405 and was thus constrainedby the existing freeway on both sides.In order to limit the disruption to traffic,all construction work for Pier 3 hadto be performed within a 20-ft-widework zone centered within the median.

Carefully designed shoring was neededwith construction tolerances limited toa few inches. The orientation of theI-405 median relative to the new bridgealignment also dictated that the bridgewould have to be placed on piers with45-degree skews.

The uneven terrain at the project sitealso played an important role in thedesign. In order to accommodate afuture on-ramp near the south end ofthe bridge, one of the two intermediate

piers had to be designed significantlytaller than the other pier. This resulted

in a significant challenge to the seismicdesign of the bridge.

Although the project scope onlyinvolved widening existing I-405 to four

lanes in each direction, the replacementbridge needed to accommodate a futurewidening adding a total of four morelanes. To meet this requirement, thelongest span of the replacement bridgeneeded to be in excess of 200 ft.

Girder SelectionC

Documents

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