VSL Construction systems - FenixEdualfaiate/rma/Construction_systems_2006... · VSL CONSTRUCTION SYSTEMS Post-tensioning Stay Cables Heavy Lifting ... Indonesia Penny’s Bay Viaducts

V S L CONSTRUCTION SYSTEMS

Post-tensioningStay CablesHeavy LiftingBridge ErectionForming systemsRepair andStrengtheningBar systemsGround anchorsVSoLDuctalBearings and JointsStructural Monitoring

C O N S T R U C T I O N S Y S T E M S

Contents

The VSL culture 3The company 4Quality, Safety and Environment 5Multistrand post-tensioning system 6Bonded slab post-tensioning system 13Monostrand unbonded post-tensioning system 17Slab on grade post-tensioning system 19External post-tensioning system 20Stay cables 22Heavy lifting 24Bridge erection 26Forming systems 28Repair, strengthening and preservation 30Bar systems 32Ground anchors 34VSoL® 36Ductal® 38Bearings 40Expansion joints 41Structural monitoring 42

The VSL culture

VSL is a solution network organisedaround locally-based subsidiariesproviding modern and cost-effectiveconstruction technologies, which aredeveloped and updated by centralisedexpert R&D and technical teams.

Our aim is always to offer not only thebest post-tensioning solutions but alsoinnovative construction techniques,designed to increase site safety, savetime, improve durability, and reducecosts.

We are always keen to work inpartnership with our clients right fromconceptual stage and have our designand method engineers working closelywith their estimating teams duringtender stage.

Our main strength is the quality of ourhighly experienced, multicultural staff.Our Marketing Staff is dedicated tolisten and understand our client’sneeds and to prepare customisedsolutions for their projects. We developnew ways of continuously training ourexperts through e-learning, video-

C O N S T R U C T I O N S Y S T E M S 3

About VSL

learning and annual workshops wherewe present our new products,equipment and techniques. We alsostimulate knowledge-sharing throughour intranet which contains referencematerial, management tools and adedicated forum where ideas aboutbest practices are exchanged.

Our ultimate goal is to deliver the bestquality service to our clients, with topquality construction techniques,backed by our experience and well-trained specialists in design, methodsand job site construction.

Subscribing to the philosophy thatwhat is good today may always bemade better for tomorrow, VSL has

La Unidad Bridge – Mexico Nina Tower – Hong KongSydney Airport –AustraliaShenzhen Western Corridor – Hong Kong

Shatin T3 – Hong Kong

R&D on CS 2000 system

Lai Chi Kok – Hong Kong

always attracted the most talentedand motivated people, all withone goal: to be your most valuedconstruction partner.

the structure, enabling efficient useof building materials while controllingdeformations under service conditions.Complying with national andinternational standards, they areapproved in every country wherethe use of post-tensioning requiresofficial certification.

Stay cables, external cables, groundanchors, heavy liftingThe post-tensioning principle is alsoapplicable to stay cables, externalcables, structural strengthening andrepair as well as ground anchors usingstrand or bar systems.VSL’s understanding of post-tensioninghas also led to the development of theVSL heavy lifting system whichprovides safe and cost-saving solutionsfor lifting, lowering and horizontaljacking of large and heavy loads andmany other applications.

Every area of concrete constructionMultistrand and monostrand systemsare used in virtually every area ofconcrete construction. While usedprimarily in bridges and buildings,VSL’s special construction systems arealso employed for the constructionof concrete containment structures,anchoring in rock and soil, lifting andsliding of heavy loads.

C O N S T R U C T I O N S Y S T E M S4

About VSL

The company

Since 1956VSL’s special construction systems havebeen used throughout the world since1956. They are technically proven andhave earned a well-deservedreputation for their quality andreliability. This has led to VSL becominga recognised leader in the field ofspecial construction systems/methodsand related engineering.

Post-tensioning as core businessVSL technology is based onthe principle of post-tensioningwhere the prestress is permanentlyintroduced into the structure afterthe concrete has hardened. This isachieved by the stressing of suitablyarranged, high-strength prestressingtendons. VSL post-tensioning generatesfavourable stress conditions in

Solution findersWith offices throughout the world,VSL offers a comprehensive rangeof professional services for any project.These locally based services includefeasibility studies, preliminary designs,alternative proposals, structural designassistance, contractor consulting andfield installation, all aimed at findingthe best solution and insuring the bestvalue for money. Our locally basedoffices allow VSL to be close to ourclients and offer our constructionsolutions effectively.

VSL networkVSL operates as a transnational groupof companies. Its subsidiaries andlicensees are organised into closelyco-operating regional units.VSL customers directly benefit fromthe continuing development of VSL’sspecial construction methods and fromthe exchange of information takingplace within the VSL Network. Thismeans that customers have localaccess to all the resources andexpertise provided by the VSL Group.The scope of VSL’s value-added servicesis tailored to suit client needs.VSL Companies are able to execute allworks using VSL personnel andequipment. This involvement includesappropriate technical consultancy andsupport during planning andconstruction phases.

Grand Central Tower – South Africa

ManhattanHeights –

Hong Kong

Batam – Tonton Bridge – Indonesia Penny’s Bay Viaducts – Hong Kong


Quality, Safety andEnvironmentVSL to be the preferred solutionnetworkTo assist in achieving this objective theVSL group has been pursuing adynamic, strong, coherent anddecentralised QSE (Quality, Safety,Environment) policy for several years.It has established a committee whosefocus is to ensure coordinationof actions, encourage sharing ofexperience and promote best practice.As a technical leader in the post-tensioning industry, VSL workscontinuously, through its qualityassurance program, to refine, improve,and expand the scope of its systemsand services. Local QSE teams arerequired to have an active and effectivemanagement system that monitorsand continuously improvesperformance.

Commitment to continuous qualityThe management of VSL is committedto continuous quality improvementthrough the participation of allemployees in the preparation,implementation and evaluation ofimprovement activities.

It is recognised that all our employeesare vitally important to ourcompetitiveness and prosperity and

with this in mind, we aspire tomaintain the highest level ofsatisfaction, health and safety of ourpeople.

The VSL Group continually strives for“zero accidents” and ensures that theirresponsibility not only extends to theirdirect employees but also to workersemployed by Subcontractors or in anyway related to the site and itsimmediate environment.

This publication represents a summaryof VSL’s special construction systemsand includes essential design andconstruction information forPost-Tensioning projects. Technicaldata and dimensions of anchorages,

cables and equipment are given inthe annexes. The dimensions andstrengths indicated are subject tochange as VSL continuously improvesits systems.Additional tendon sizes are availableupon request. Alternate dimensions,special conditions and variousstrengths may all be accommodated.Your local VSL Representative willfurnish additional details regardingspecific applications.

Services for fully customised solutionsThese services aim to provide fullycustomised solutions adapted tocustomer requirements. VSL offerscustomers the strength andflexibility of a world-wide network.VSL’s goal is to be a privileged partnerand to help find the best-adaptedsolutions to particular needs.

Sucharskiego Bridge – Poland

Industrial Ring Road – Thailand

Avignon Viaducts – France


Multistrandpost-tensioning

Main characteristics

The VSL multistrand system is characterised by thefollowing features:• Standardized tendon units using up to fifty-five

13mm (0.5”) or 15mm (0.6”) diameter strands;• Wide selection of anchorage types;• Steel or plastic PT-PLUS® ducts;• VSL HPIR grout or other types of grouting;• Tendons manufactured on-site or in the factory;• No need to determine tendon length in advance;• Simultaneous stressing of all strands in a tendon, with

individual locking of each strand at the anchorage point;• Stressing carried out in any number of phases;• Simple and reliable equipment for installation, stressing

and grouting.

System description

Technical data and dimensions are given in the annexes.For reasons of clarity and simplicity, anchoragereinforcement are not shown in the pictures. Primary

bursting and secondary equilibrium reinforcement form anintegral part of the anchorage and are required to controllocal zone stresses. For more detailed information on theanchorage zone design, see VSL’s Report Series on “Detailingfor post-tensioning”.

Sines tank – Portugal CS 2000 at Medway Bridge – UK Electrically Isolated Tendons (EIT)CS 2000 on high speed rail Anoia – Spain

VSL HPI® grout or other types of grouting

Type EThe prestressing force is transferred to the concrete by abearing plate. If necessary, the spiral can be replaced bysuitably laid out orthogonal reinforcements.

Type ScThis is a compact and easy to handle anchorage system.If necessary, the spiral can be replaced by suitably laid outorthogonal reinforcements.

Type StrongholdThis compact and easy to handle anchorage system allowsprestressing force to be transferred through two flanges.If necessary, the spiral can be replaced by suitably laid outorthogonal reinforcements.


Live anchorages

Type CS 2000This revolutionary anchorage has a composite bearing plate(metal - high performance concrete) and is lighter, smallerand easier to handle. It comes in 3 different configurations:CS 2000 - STANDARD for normal applications,CS 2000 - PLUS using VSL’s PT-PLUS® duct systemfor enhanced corrosion protection or improved fatigueresistance, and CS 2000 - SUPER able to provide anelectrically isolated tendon.

Type GcThis is a compact and easy tohandle anchorage system.If necessary, the spiral can bereplaced by suitably laid outorthogonal reinforcements.

All VSL stressing anchorages can be used as a dead-end anchorage if access is provided. For dimensions of anchorages see annexes.Anchorage components are not available in all countries. Please check with your local VSL office for availability.

Duct

Grout connectionCS trumpet

Strands

Wedges

Anchor head

Bearing plate

Protection cap

Grout tube

Duct

Duct

Sleeve

Wedges

Strands

Anchor head

Bearing plate (steel)

Anchor head

Anchor head

Bearing plate

Grout inlet

Duct

Bearing plateWedges

Wedges

Strands

Strands

Duct

Plastic trumpet

Bearing plate

Couplers and intermediateanchorages

Coupler Type KCThis fixed coupler is used for connections to a cable that hasalready been installed and stressed. The strands areanchored using compression fittings positioned onto thecoupling head grooves.

Coupler Type StrongholdThis fixed coupler is used for connections to a cable that hasalready been installed and stressed. The strands areanchored using compression fittings positioned onto thecoupling head grooves.

Coupler Type VThis movable coupler is used for connecting to a cable thathas already been installed but not stressed.The strands of the new cable are anchored usingcompression fittings positioned onto the coupling headof the previously installed cable.


Multistrand post-tensioning

Intermediate anchorage Type Z and ZUIntermediate anchorages are used for those tendons wherethe ends cannot be fitted using normal stressinganchorages.The anchorage head is loosely placed in the blockout andmoves during the stressing operation on the tendon axis.Z type intermediate anchorages are used:

• For pressure shaft and pressure tunnel ring tendons,avoiding the use of internal buttresses;

• For silo and reservoir circular structure ring tendons,avoiding the use of external buttresses;

• For frame, arch, foundation rafts and shell structuretension ties where there is no or limited access to endanchorages.

The VSL type ZU intermediate anchorage has similarapplication possibilities as type Z. It is particularly adaptedto small cable units in structures without dynamic loading.

For dimensions of couplers and intermediate anchorages see annexes.Anchorage components are not available in all countries. Please check with your local VSL office for availability.

Coupling head K

Duct

Compression fittingswith retainer plates

Tension ring

Sleeve

Wedges

Grout tube

Tension ring wiyh anchors

Retainer plate

Anchor head ZU

Anchor head ZWedges

Duct

Compression fittings

Steel band

Bearing plate

Tension ring

Sleeve

Coupling head K

Grout tube

Wedges

Dead-end anchorages

VSL Type PThis type of anchorage is used where the prestressing forcehas to be transferred to the structure at the far endof the tendon. It consists of a plate incorporating holesfor the strands to pass through. The strands are anchoredusing compression fittings bearing onto the plate.The compression fittings are locked into position bya retainer plate. Where the force shall only be transferredto the concrete using a bearing plate, polyethylene tubescan be used to sheath the strands between the end of theduct and the bearing plate.

VSL Type HThis type of anchorage is the best solution when strandsneed to be pushed through on site.The prestressing force is transferred to the concrete partiallyby bond and partially by end bearing (bulb). The spiral(for 5-7 / 6-7 and larger units) and tension ring preventinadmissible stresses due to deviation forces acting on theconcrete. The rebar net at the anchorage end zone acts as aspacer for individual strands.

VSL Type AFThis type of anchorage is used for vertical tendonsinstalled once a structure is concreted, where theprestressing force has to be transferred to thestructure at the lowest end of the tendon and whenthere is no access to the dead-end anchorage. Thestrands are placed in the tendons with compressionfittings at their lower ends, which are then bondedinto the AF anchorage with a special cement AFgrout. Once the AF rout anchorage has achievedsufficient strength the tendon can be stressedfrom the live anchorage and then grouted.

VSL Type LThis type of anchorage is used for tendonsinstalled once a structure is concreted andwhere there is no access to the dead-endanchorage. It is often used forvertical tendons in reservoir walls,for nailing pier head segments topiers in segmental bridgeconstruction, or for horizontaltendons in slabs or foundationrafts. The strands are installed intothe duct after concreting andsimultaneously stressed using jacksat both stressing anchorage ends.

VSL Type LDWhen loops with a smaller radius are required, special halfround ducts are available upon request. VSL type LD Loopsare available with a 590mm radius. The tendon sizesavailable are the same as type L, the difference is the ductconfiguration as indicated. A tight radius is good for nailingof precast segments to piers.


Seal

Duct B

Duct A

Grout tube

Grout tube

Spacer

Bulbs

Tension ring

Duct sized such thatonly two (2) layers of

strand occur in the loop.

For dimensions of dead-end anchorages see annexes.Anchorage components are not available in all countries. Please check with your local VSL office for availability.

Duct

Grout tube

Retainer plate

Duct

Seal

P-plate


Tension ring

Sheathing andcorrosion protection

For conventional applications,corrugated steel ducts with aminimum wall thickness of 0,25mmare used, however, the VSL PT-PLUS®system with its corrugated plastic ductand plastic coupler can provide anumber of important advantageswhen compared with conventionalstee ducts. For applications requiringenhanced corrosion protection andimproved fatigue resistance of thetendons, use of the VSL PT-PLUS®System with corrugated plastic duct isrecommended.This fully encapsulated, watertightsystem offers superb corrosionprotection, and the plastic ducteliminates fretting fatigue betweenthe strand and duct.

The PT-PLUS® system is suitable for allapplications but, given its specificcharacteristics, is best adapted to:

• Transverse tendons in bridge deckslabs and wherever tendons are closeto the concrete surface;

• Railway bridges and other structureswith high fatigue loadings or subjectto stray electric currents;

• Structures where severe corrosiveenvironment may be expected;

• Tendons that need to be electricallymonitored throughout the structure’sservice life.



All ducts are manufactured in a varietyof standard lengths and are coupledon site.

Main advantages are:• Greatly enhanced tendon corrosion

protection;• Improved tendon fatigue resistance;• Reduced sensitivity to stray electric

currents;• Reduced duct friction coefficient;• The PT-PLUS® system, when used

with VSL anchorages, can be adaptedto provide electrically isolatedtendons (EIT). These tendons may beelectrically monitored at any timethroughout the life of the structure.

Tendon profile

PT-PLUS® duct

Plastic duct PT-PLUS®Steel duct

For diameters of ducts see annexes.

Plastic duct PT-PLUS® and vent

Selected designconsiderations

Spacing and cover of ductsWhen determining minimum spacingand concrete cover requirements,reference should be made to applicablestandards and recommendations.

Tendon supportsRecommended spacing:Standard steel ducts 0.8 to 1.2mPT-PLUS® ducts 0.6 to 1.0m

Tendon force lossesThe effective prestressing force ata specific placeand time differs from the initialprestressing force.There are several reasons for this.Significant factors include:• Friction losses due to the curvature

of the tendon;• Concrete shrinkage and creep;• Relaxation of the prestressing steel;• Draw-in of the wedges during lock-off.

Friction losses along the tendoncan be determined using the followingformula:Px = Po.e-(μα + kx), in which:x = distance from stressing end

(in meters);Px = prestressing force at x;Po = prestressing force at stressing end;


Minimum radius of tendon curvaturesand minimum straight length forinternal bonded tendons

Minimum breaking load of tendon (MN)

10mm nominal

10mmnominal

Edge distances

E

E

Tendon unit E (mm)

StrandTYPE

12.7mm

5-75-125-195-275-425-55

305050808080

15.2mm

6-76-126-196-276-426-55

50508080

100100

k = 0.001 (range: 0.0008 to 0.0012)

To calculate losses due to concreteshrinkage and creep, reference shouldbe made to the technical documentsand standards applicable to eachproject.

The relaxation of the prestressing steeldepends primarily on the type of steel(relaxation class), the extent of theprestressing, and the temperature.

For the low relaxation strandscommonly used today, maximum lossis 2.5% after 1,000 hours at 20°C withan initial stressing at 70% of thenominal tensile strength. Furtherinformation can be found in therelevant prestressing steel standardsand manufacturers’ literature.

Independent of the jack or tendontype, a loss of approximately 6mm dueto wedge draw-in occurs at lock-off.If necessary, compensation can beprovided by appropriate procedures.

μ = friction coefficient;α = sum of all angular deviations

(in radians) over the distance x;k = wobble friction coefficient due

to minor unintentional tendoncurvatures (installation tolerances).

The μ and k friction coefficients canvary fairly widely and depend uponseveral factors, including: the natureand surface condition ofthe prestressing steel; the type,diameter and surface condition ofthe duct, and the installation method.

The following values may be assumedfor design:• Tendon in standard steel ducts:

μ = 0.2 (range: 0.16 to 0.22)k = 0.001 (range: 0.0008 to 0.0012)

• Tendon in PT-PLUS® plastic ducts:μ = 0.14 (range: 0.12 to 0.15)

Minimum radiusof tendon curvature Minimum straight lenght



Placing of anchor head and wedges

Positioning of jack

Stressing

Seating of wedges

Placing of anchor head

Positioning of jack

Stressing, measuring, seating of wedges

Grouting of tendon

For dimensions of the jacks, please see annexes.For more information on VSL HPI® grouting, please refer to the VSL HPI® grouting brochure.

Stressing

The unique feature of the VSL post-tensioning system lies in its specialwedge locking procedure. The wedgesalways remain in contact with thestrands during the stressing operation.As the pressure in the jack is released,the wedges automatically lock in theconical holes of the anchor head.

Grouting

The objectives in grouting a tendon are twofold:1. To provide an effective corrosion protectionsystem, by filling the free space in the tendonwith the grout which provides an alkalineencapsulation of the tendon, and2. To achieve an effective bond between thetendon and the surrounding concrete.It is therefore essential that grouting be carriedout in a carefully monitored and controlledmanner. Through extensive R&D VSL hasdeveloped a detailed understanding of both thechemical and practical aspects that affect groutquality and has produced specific groutingprocedures and grout mixes which are tailoredto suit local conditions and material properties– VSL’s HPI® high performance cimentitionsgrouts. VSL uses combined mixer and pumpunits to ensure control over the grout qualityand delivery on-site and can also providevacuum assisted grouting procedures for certainspecial applications such as long cables, externaltendons or electrically isolated tendons.

Construction sequence

Today’s building owners and designersneed to provide a high level ofstructural flexibility to meet changinguser requirements.

Post-tensioning provides greater spanswith reduced structural floor depths,resulting in larger column-free areas.As a result, internal layouts are notdictated by tight column grids. Positivedeflection and crack control and,if necessary, joint-free water-tight slabs,free designers from the limitationsof traditional reinforced concretestructures. VSL post-tensioning is moreeconomical than other systems,especially when fast constructioncycles are envisaged. There is lessmaterial handling on site and

a reduced labor force, minimizing sitecongestion. Most importantly, thereis the quality and service provided byVSL’s specialized highly efficient teams.

The VSL bonded post-tensioning slabsystem has been used in manyprestigious buildings, bridges andother structures. The system uses upto five strands 13mm (0,5”) or 15mm (0,6”)contained in flat-shaped ducting,and anchored in a single anchorage.

Strands are individually stressedand gripped by wedge action. Afterstressing, the duct is filled witha cement grout that fully bonds thestrands to the surrounding concrete.


Bonded slabpost-tensioning

Placing tendons Concreting Stressing Grouting

AL Faisaliah Riyadh – Saudi Arabia

Dubai Festival – Saudi Arabia Kens – Australia Nina Tower – Hong Kong


Bonded slab post-tensioning

Live anchorages

VSL Type SO

VSL Type Bondtech VSL Type S5 – 2 VSL Type S5 – 1, S6 – 1

VSL Type S

Lugo hospital – Spain Pórtico building Madrid – Spain

Grout tube

Recess former

Strands

Strands

StrandsAnchorage body

Flat duct

Duct

Wedges

Trumpet

Recess former

Casting

Anchor block

Duct

Recess former

Wedges

Grout tube Grout tube

Strands

Strands

Wedges

StyreneRecess former

PlasticRecess former

Grout tube

Duct

Anchorage

Wedges

Duct

Cast inanchorage

Cast inanchorage

Barrels&Wedges grips

For dimensions of anchorages see annexes.Anchorage components are not available in all countries. Please check with your local VSL office for availability.

Grout tube

VSL Type SK


Couplers

Dead anchorages

VSL Type S

VSL Type H

VSL Type N

Coupling head SK

Tension ring

Tension ring

Flat duct

Duct

Flat duct

Flat duct

Trumpet

Bearing plate Cast in anchor

Strands

Steel band

Sleeve

Spacer

Bulb


Grout tube

Grout tube

Grout tube

Grout tube

Grout tube

Seal

VSL Type P


Individual anchorages

P-plate

Flat duct

Tension ring

Anchor head


Cast coupling block

Vincom Towers – Vietnam Magarpatta – India

For dimensions of couplers and dead anchorages see annexes.Anchorage components are not available in all countries. Please check with your local VSL office for availability.

Grout tube

RBC Plaza – Philippines


• Spacing of tendon supports:0.75 to 1.2m (steel ducts)0.75 to 1.0m (PT-PLUS® ducts)

• Minimum curvature radius:2.5m (vertical profile)6.0m (horizontal profile)

• Min. straight length at anchorage:0.75m

• A wedge draw-in of approximately6mm occurs at lock-off

• Friction losses can vary fairly widelydepending on factors such as surfacecondition of strands, duct types andsurface condition, materialproperties, installation methods andon-site workmanship. Generallyspeaking, the following frictionparameters can be used.


Bonded slab post-tensioning

• Tendons in standard steel ducts:μ = 0.20 (-) (range: 0.16 to 0.22)k = 0.001 (m-1) (range: 0.0008 to0.0012)

• Tendons in PT-PLUS® ducts:μ = 0.14 (-) (range: 0.12 to 0.15)k = 0.001 (m-1) (range: 0.0008 to0.0012)

The friction losses in the anchoragedue to curvature of the strand andfriction of the strand in the wedgesusually amount to:

•Edge stressing 3% average•Internal pocket stressing 5% averageThe PT slab method allows designers toreduce building heights or to increasefree heights between floors.

Traditional design PT slab design

Free height

Free height

Free height

Free height

Height saving

Bellvitge Barcelona – Spain

Vodaphone building – Egypt

approximately 1mm wall thickness.The monostrands are installed eithersingly or in bundles of two, three orfour. Each strand is individuallyanchored, stressed and locked-off.

To ensure continuous corrosionprotection, special sleeves are used tojoin the sheathings to the anchorages.Anchorages can be equipped with aprotective cap.

Monostrands feature factory-appliedcorrosion protection, very low frictionlosses, and permit the structural depthto be fully utilised.

These light, flexible monostrands canbe easily and rapidly installed, andbecause there is no grouting, theyusually lead to economical solutions.

In design, the different post-crackingbehaviour of unbonded versus bondedsystems should be considered. Detailedinformation is given in VSL’s “Post-tensioned slabs” publication.With certain adaptations, the VSLmonostrand unbonded system canalso be used for post-tensioningmasonry walls.

17

Monostrand unbondedpost-tensioning

El Golf 2001 – Chile Metropolitan – US

Tendon characteristics• 13mm/15mm diameter strandin accordance with the relevantprestressing steel standards.• External diameter of the plasticsheathing: approximately 16mmand 18mm (0,5”) respectively.Permanent corrosion-preventinggrease and plastic sheathing inaccordance with fib/PTIrecommendations (0,6”).


Hilton Buenos Aires – Argentina

System description

The VSL monostrand unbonded systemhas advantages similar to thoseof the VSL bonded slab post-tensioningsystem.

The VSL monostrand unbonded systemuses 13mm (0.5’’) or 15mm (0.6”)diameter strands, which are givena coating of permanent corrosion-preventing grease and are enclosedin an extruded plastic sheathing.

The grease and plastic provide doublecorrosion protection, as well aspreventing any bonding between thestrands and the surrounding concrete.The plastic sheathing is usually inpolyethylene or polypropylene with


Monostrand slab post-tensioning

Anchorages

VSL Type S

VSL Type ST System

VSL Type SF

For dimensions of anchorages, stressing jacks, reinforcement of the anchorage zone and design values see annexes.Anchorage components are not available in all countries. Please check with your local VSL office for availability.

Recess former

Sleeve

Anchorage

Transition cone

Coupling head andthreaded coupling

Monostrand 2

Sleeve

Sleeve

Monostrand 1

Recess former

Monostrand

Wedge

Installation nut

CapAnchorage body (casting)Sleeve

Wedge

Wedge

Monostrand

Strand

Installation piece

Anchorage body (casting)

Monostrand

Couplers

Coupler type SK


Slab on gradepost-tensioning

Tenax – ItalyColes Myer – Australia

Characteristics

The VSL post-tensioning system iswidely used in the construction ofslabs on grade. Warehouses,distribution centres, containerterminals, airports, pavements,residential slabs and recreational slabsfor tennis courts and skating rings arecommon applications.

Eliminate jointsJoints in reinforced concrete slabs ongrade have long been a cause of costand delay to owners because of theconstant maintenance they require.Owners and operators of facilities withslabs on grade can eliminate thesecosts by eliminating the jointsthemselves. The VSL post-tensionedconcrete slab on grade is cast in verylarge areas, often exceeding 2 500m2,in which there are no joints. In certainapplications, slabs in the order of10 000m2 have been constructedwithout movement joints.

Crack-free performanceThe VSL post-tensioning axiallycompresses the concrete slabto counteract tensile stresses which

would otherwise cause cracking underthe worst combinations oftemperature and applied loads. Theprestress applied can even control theinitial concrete shrinkage sufficientlyto prevent initial shrinkage cracking.

Thinner slabThe VSL slab is much thinner than itsequivalent in reinforced concrete, andgenerally contains no reinforcementexcept at the perimeter andfor trimming at penetrations.

Initial costThe thinner slab, absence ofreinforcement, absence of costly

internal jointing and the cost savingavailable from the constructionprogram time saved by casting largeareas, all contribute to a competitiveinitial cost.

Future maintenanceDuring the life of the slab, the jointmaintenance costs which the ownerno longer needs to provide, will reapgreat improvements in the efficiencyof the facility.

A life cycle analysis can be readilyundertaken to demonstrate that futuresavings to the ownermore than justifythe selection of a VSL slab on grade.

Austrack – AustraliaNestlé plant – Chile

System description

External post-tensioning is welladapted to bridges due to the resultingreduction of congestion inside theconcrete and the high degree ofcorrosion resistance provided by thesystem. External tendons are easy toinspect and, if necessary, replace.They are ideal for strengtheningexisting structures and, apart fromtheir uses in bridges, can be usedfor a wide range of other applications,including buildings, silos and reservoirs.

VSL external tendons comprise:• Strand bundle;• Polyethylene ducts;• Standard multistrand anchorages,

and special anchorages permittingcomplete tendon replacement;

• Grouting compound.

A wide selection of VSL anchoragetypes is available to meet thefull range of practical requirements.In addition to the anchoragesillustrated here, intermediateanchorages are also available.The strand bundle can be assembledfrom uncoated or individually greasedand sheathed strands. The anchoragesfor these two types of tendon differonly in detail, the principle remainsthe same.


Externalpost-tensioning

Stressing anchorage Strand bundle and sheath Stressing anchorage

Carrière Viaduct – France Bras de la Plaine – Reunion IslandBoulonnais Viaducts – France

VSL external post-tensioning system components


Saddles at points of deviationA saddle at a point of deviationconsists of:• A structural element capable ofcarrying the loads exerted bythe tendon in the deviation zone;• A part ensuring the geometry ofthe deviation.

Globally a saddle at a point ofdeviation must satisfy the followingrequirements:• Withstand both the longitudinal andtransversal forces that the tendonapplies to it and transmit these forcesto the structure;• Ensure, without unacceptableangular deviation, the connectionbetween two straight tendon sections;• Unless otherwise stipulated in thecontract, enable removal of the tendonwithout traumatic effect on thestructural elements;• Withstand movements of externaltendon during stressing withoutcompromising the tendon's corrosionprotection system.

Various solutions have been usedin practice, as shown in the sketch.In most cases, saddles consist ofa pre-bent steel tube cast into thesurrounding concrete or attached toa steel structure by stiffening plates.The connection between the freetendon length and the saddle mustbe carefully detailed in order not todamage the prestressing steel by sharpangular deviations during stressingand in service. It is also important thatthe protective sheath be properlyjoined. If tendon replacement isa design requirement, the saddlearrangement must be chosen


accordingly, i. e. double sheath asshown on alternative (3) of the sketch.

Minimum tendon radiiMinimum tendon radii as recommendedin Table 1 must be respected in order toavoid damage to the prestressing steeland the plastic sheaths, as well as tothe outer tubing. It is well-establishedthat friction problems may occur iftendon radii are too small.

Table 1: recommended minimum tendon radii

For dimensions see annexes.Anchorage components are not available

in all countries. Please check with yourlocal VSL office for availability.

For more information on external post-tensioning,please refer to VSL Report N° 1.

Tendon size(VSL tendon unit)up to 5-19 or 6-12up to 5-31 or 6-19up to 5-55 or 6-37

Minimum radius(m)2.503.004.00

Arrangement at point of deviation

SSI 2000 description

VSL stay cable systemThe VSL stay cable system wasdeveloped to meet the stringentdesign, construction and maintenancerequirements of cable-stayed bridges.

The VSL stay cable system comprises• a tendon formed from multiple and

parallel 15-mm (0.6") dia. high tensile7-wire steel strands;

• a greased or waxed strand, with atightly extruded plastic sheathing.

• an outer thick-walled plastic staypipe;

• factory prefabricated anchorages.

The system features are as follows• 200 MPa minimum fatigue resistance

at 45% of tendon capacity over2,000,000 load cycles;

• high degree of corrosion resistanceusing multi-layer corrosion protection;

• an extruded coating providingexcellent strand corrosion protectionduring construction;

• individual strand encapsulation andsealing in anchorages;

• easy installation of the strands intothe erected stay pipe (single strandinstallation);

• all strands are parallel with no risk oftwisting;

• single strand stressing;• no requirement for on-site cable

grouting;• easy tendon force monitoring and

adjustment throughout the cable’sservice life;

• ability to remove and replaceindividual strands withoutdismantling the installed anchorages,or the entire cable at any time;

• system adapted for the initial orfuture installation of an anti-vibration damper.

Characteristics

Compactness • reduced size of the anchorage for

easy installation and savings in thecost of the structure.

Aesthetics• using coloured co-extruded stay

pipes, different colours can beobtained;

• vibration damping devices can beplaced at the end of the guide pipesnear the deck.

Dynamic stability of the cables• stay pipes with external helical ribs to

suppress rain-wind inducedvibrations;

• the stay cable system is adapted forthe initial or future installation ofanti-vibration dampers.

• the new generation of VSL friction or Gensui dampers dampers to offerminimum maintenance duringextended design life.

DurabilityA high degree of corrosion protection:• each strand is individually protected

not only in the stay pipe, but also inthe transition part of the anchorage;

• individual anchorage sealing jointsprotect each strand not only inservice, but also during bridgeerection;

• VSL’s stay cable system has theunique feature of providingcomplete encapsulation for eachindividual monostrand along thefree length and into the anchorage.

Stay cables

22

Udevalla Bridge – Sweden

High fatigue resistance200 MPa with an upper load

of 45% of the stay capacityover 2x load cycles; excellent

ultimate resistance afterfatigue testing (min. 95% ofthe specified stay capacity).

Increased corrosion protection Factory-applied individual

protection treatment, up to 100 years design life in the most

aggressive environments.

Full encapsulation Each strand separatelyprotected inside the anchorage.

Compatible with modern construction methods

Compact anchorages fully prefabricated inworkshop, no anchorage component

assembly on the deck, single strandinstallation with light equipment, easy

force monitoring and adjustment.

STRESSING ENDWITH ADJUSTABLE ANCHORAGEPROTECTION CAP TRANSITION LENGTH


SSI 2000 Stay cable system

VSL stays with architectural barsVSL architectural bars are particularlysuitable and economical for shorterroad bridges, pedestrian bridges andstays for suspended roofs.

Single strand monitoringVSL has designed a compact load cell,the SSI 2000 Hc160, to monitor theload on a single strand within a staycable. This new equipment fits overone strand and sits on the anchor headof the stay cable between adjacentstrands, making it easy to install andreplace. This load cell offers aneconomical way to have a goodindication of the total force on the staycable.

23

Replaceablestrands Ability to remove and to replace individual strands on demand.

VersatileDesigned to receive in the future vibration dampingsystems (friction dampers) if necessary.

Increased stay anchorage protectionDeviator placed in the guide pipepovides an additional level ofprotection by filtering cable bendingstresses before they reach theanchorage.

Economical Faster installation and erection cycles.Reduced maintenance.

STAY FREE LENGTHWITH DECK CONNECTIONGUIDE DEVIATOR


Industrial Ring Road – Thailand

Europa Bridge – Portugal

Yarrade Boulevarde Bridge – Australia

Friction damper on Uddevalla Bridge – Sweden

La Unidad Bridge – Mexico

Unlike systems used by competitorswhich compromise the encapsulationnear the anchorage point and resultin potential exposure of the entirecable, VSL’s stay cable systemreduces the potential exposure to asingle strand.

Reduced maintenance costs• easy corrosion control of anchorage

components;• good access to vibration dampingsystems.

Stay cable installation• system optimised for strand-by-strand installation, with easilyhandled, lightweight equipment andreduced construction loads on thebridge during construction.

For more information on VSL stays, please refer to the VSL Stay Cables brochure.

For more information on architectural bars,please refer to the VSL Architectural bars brochure.

The Hc 160 VSL monostrand load cell

Neva Bridge – Russia

Custom engineeredsolutions for tough jobs

For economic or technical reasons,today’s civil engineering structures andindustrial plants are often assembledfrom large, heavy, prefabricatedcomponents. VSL Heavy Lifting willoften provide the most effectivesolution for projects where cranes or other conventional handlingequipment cannot be used.

Individual solutionsVSL can plan lifting, horizontal jacking,or lowering operations and design the

necessary temporary structuresneeded to meet your requirements.

SafetyThe safety of your personnel and worksis VSL’ s first priority. Our specialisedhydraulic lifting equipment is designedto provide the highest level ofreliability, and VSL field services arebased on a total commitment to safety.

FlexibilityOur equipment includes a largenumber of hydraulic strand units, jacks,pumps, control units, monitoringdevices and modular lifting /jacking

frames, giving us the capacity toperform virtually any projectrequiring lifting, lowering or horizontaljacking.


Heavy lifting

Waldstadion – Germany

International Exhibition Centre – Hong Kong

VSL service packageOur approach is flexible, and the rangeof our services is tailored to the specificproject requirements. They include:• feasibility studies and preliminary

consultation;• project design and planning;• design, manufacture, and supply

of special equipment;• leasing of VSL equipment and

execution of work.

Proven equipment forhandling heavy loads

VSL strand systemThe main components of the VSLstrand system are the motive unit,the tensile member with theanchorage for the load, and the pumpwith its controls.

Motive unitThe motive unit consists of ahydraulic centre hole jack with upperand lower anchorages. During liftingthe jack is extended, causing theindividual strands of the tensilemember to be gripped by the upperanchorage and thus to be movedupwards. At the start of the pistons

downward movement, the strandsare immediately gripped by thelower anchorage. In this way, theload is raised using a step-by-stepprocess.For lowering operations, VSL’ s motiveunits are equipped with an auxiliarydevice which automatically controlsthe opening and closing of theanchorages.

Tensile memberThe tensile member consist of 15 mm(0,6”) strands. The tensile member isanchored to the load by a speciallydesigned end anchorage.

Hydraulic pumpsVSL electro-hydraulic pumps can bemanually controlled or operated ingroups from a central control board.

VSL has a wide range of pumps witheither single or multiple outlets. Thecharacteristics of these pumps ensurethe synchronised movement of thejacks. Pressure control devices allowforces to be monitored at all times.The movement speed varies accordingto the project and, if required, can be inexcess of 20 m / hour.

Control and monitoring systemsThe lifting of hangar roofs or ofsimilar statically overdeterminedstructures usually requires thatlifting movements be precisely co-ordinated.This is achieved by specially designed,computer-based multi-pointmonitoring systems, which allow theoperation to be centrally controlledand monitored up to the final,precise height.

Special hydraulic equipmentOur range of equipment also includes a large number of different hydraulicjacks. VSL can also design and supplycustom-built hydraulic systems forspecial applications.


Burj Al Arab - Dubai Herradura - Spain

Airbus 380 hangar roof lif – France

For more information, please refer to the VSL Heavy Lifting brochure.

VSL experience

With extensive experience in largeinfrastructure and superstructureprojects, VSL has a proven record ofdeveloping project specificconstruction systems and methodsthat promote highly efficient rates of

construction and facilitate programmeschedule, while maintaining and oftenimproving essential safety and qualitycontrol measures. Lateral thoughtprocesses encouraged within thedesign and production teams provide a suitable environment in which tonurture novel, and often remarkably

simple solutions to demandingproblems. The exchange of knowledgewithin the VSL global network enablesthe group’s considerable experience tobe fully utilised and applied in a widevariety of engineering domains.As a specialist bridge partner, VSL canbring the project team an extensiveexperience gained from erecting over100,000 precast bridge deck elements(providing almost 5 million squaremeters of bridge surface) and alsoconstructing multiple insitu bridgesutilising VSL form travellers andincremental launching methods.VSL is committed to offering clients a ”best for project” service that hasrecently led to the development andsuccessful implementation of variousinnovative Partnering and Alliancingarrangements that have proved to behighly successful and mutuallybeneficial to all parties involved.


Bridge erection

West Sydney Orbital – Australia

Shatin T3 – Hong Kong

VSL slipform

The VSL Slipform System has been usedin the construction of silos, storagetanks, containment structures,chimneys, cooling stacks and bridgepiers and pylons for over 20 years.Slipforming is advantageous whenrapid construction between 2 and 6 mper 24 hours is required which resultsfrom continuous working it forms a monolithic structure free fromconstruction joints. The system is raisedby hydraulic jacks with upper workingplatforms for reinforcement fixing andconcrete placement and a suspendedscaffolding for finishing works.

VSL climbform

VSL has also been active inClimbforming for over 20 years.The VSL Climbform System is a selfclimbing heavy duty constructionplatform used primarily to lift staticpanel vertical wall formwork.The system provides the wall designerwith complete flexibility in both thestructural design and selection offinishes. The system is particularlyadapted to the construction of high-rise building cores. The 6-m high VSLClimbform has three platform levels,

and the formwork panels hangingfrom the external frame and internalplatforms permit pours over a heightof 4.2 m. The internal steel platforms,incorporating the formpanel hooks androllers, are specifically designed andmanufactured for each project,guaranteeing accurate and economicassembly operations.

VSL Climbform permits an excellentproduction ratio with accurate placingof door frames, openings, blockouts,cast-in components and direct placingof prefabricated reinforcement cages.Another advantage lies in the safety ofthe Climbform. The VSL service packageincludes: feasibility studies andpreliminary consultation and pricing;tender design and planning; design,manufacture and supply of equipment;leasing, training of site-staff,supervision of the works for the firstfew levels, followed by dismantlingoperation.

Standard features include:• Custom designed formwork panels

which may be ganged in any shape or size to lift as one unit

• form heights ranging from 2.5 to 4.2metres

• unobstructed access to the forms forcleaning and oiling, fixing of door

frames and blockouts as well asreinforcement and reinforcing fabricfixing, including prefabricatedreinforcement

• truss members of fixed heightassembled in "Meccano like fashion"to form a platform of any plan shapeor size

• easy levelling and plumbing of theexternal platform, which is typicallysupported on four, six or eightseatings

• minimum adjustment of individualforms after the initial set-up

• an achievable vertical tolerance rangeof 10mm per 4.2 metre height

• variation of wall thickness by movingthe internal or external forms

• parking the internal platforms atmid-lift to facilitate blockout andreinforcement fixing, eliminating therequirement for temporary scaffolds

• cycle times as low as three days• access to external walls for curing• hanging access stairway.

Optional features include:• steel formwork to enable pouring

within 50mm of boundaries• support of concrete placing booms on

the platform• access hatches and/or temporary

removal of platforms to installprecast stairs

28

Forming systems

Almeria – Spain Angara Bridge – Russia


• external trailing platforms • internal trailing platforms to allow

early installation• support of site sheds and toilets on

the platform• provision to allow manhoists to

service the top working platform• provision to locate tower cranes

within internal and corridorplatforms

• collapsible door formers• trailing formwork and platforms for

vertical and raking walls.

VSL form travellers

VSL Form travellers have beendeveloped in conjunction with the in-house design of balanced or freecantilevering bridge structures.The form traveller of either overheadtruss or underslung type, is ahydraulically driven falsework systemwith built in working platforms andformwork panels designed to provide a rigid frame to minimize deflectionsunder load.

System flexibilityThe VSL Form traveller system isdesigned for a variety of segmentlengths varying from 3m to 5.5m andcan support concrete and formworkloading from 100t to 450t. The traveller

system design can accommodate widevariations in segment length, height,web thickness and deck width andgeometry. Vertical deflections at theleading edge of the traveller assemblyare less than 25mm at maximum loads.

System operationThe VSL Form traveller system iseconomical and efficient to use.Launching is accomplished byadvancing the system forward on rails.The interior formwork remains withinthe previously poured section in orderto facilitate the placing of thereinforcing steel in the bottom slaband webs of the new segment.The segment construction cycle cangenerally be carried out in less than a week. A typical segment cycle wouldconsist of the following steps:

1. The system is launched on rails to thenew segment location.

2. The external formwork is aligned,levelled and fixed into place.

3. Reinforcing steel is placed in thebottom slab and web walls.

4. The interior formwork assembly isadvanced, and the top deck slabsoffit and wall forms are levelled andfixed into place.

5. Reinforcing steel and post-tensioningtendons are placed in the deck slab.

6. Placement of concrete in bottom

slab, web wall and deck slabconcrete.

7. Stressing of post-tensioning tendons.8. The internal and external formwork

is stripped from the cast and curedsegment and the VSL Form traveller islaunched to the next segment.

VSL servicesVSL provides design, fabrication,material supply and installationservices to the balanced cantileverconstruction process. Our engineeringteam supports the custom design ofthe Traveller System to meet the needs of a specific project and bridgeconfiguration. Complete systemdrawings and operation manuals detailall aspects of traveller operation forease of assembly and safe operation.VSL is ready to provide technicalassistance and field supervision oftraveller 1st assembly andcommissioning, launching,maintenance and dismantling or atotal turnkey package incorporatingthe operation of the system with thepost-tensioning application.

29C O N S T R U C T I O N S Y S T E M S

Kaoshiling Mass rapid transit system – Taiwan

For more information, please refer to the VSL Bridge Erection brochure.

Stonecutters Bridge – Hong-KongSinu Bridge – Spain

Upgrading deficient -but in servicestructures is a challenging andgrowing segment of the constructionindustry. VSL strengthening systemsare providing economical solutions for structures requiring load capacityupgrade or improvement due tochange of use, deterioration orconstruction defects.

Structural appraisal and diagnosisStructural remedial work demandsthorough diagnosis ofdamage/deterioration and fullassessment of causes, risks andconsequences involved.

VSL employs state-of-the-artequipment and special inspectiontechniques to detect any defects inconcrete, reinforced concrete, andprestressed concrete structures beforeany significant damage occurs.Close cooperation with materialtesting institutes, structural designersand the latest investigation techniquesenable VSL to prepare precise andcomprehensive reports such as:• Inspection and surveyance of

concrete structures


Repair, strengthening andpreservation

Fallingwater – USA

Pisa Tower - ItalyLaayoun Wharf – Morocco

• Condition evaluation of concretestructures

• Root cause analysis• Design of repair strategies• Badget costing.

To repair or not to repair…….Once the external signs of a structuralproblem have been observed, the nextstep is critical: to identify theunderlying cause.

Any decision to repair – and the repairstrategy- should never be based solelyon effect. It should always arise froman analysis of the cause.

A solid understanding of the root causewill help determine whether theobserved effect actually warrants a repair.

Many owner-related issues must alsobe assessed - safety, environmentaleffects, change of structural usage,new design loads, and risk level,to name just some – before a wisedecision can be made to repair or not to repair.

Tailor-made systemsVSL is a one-source solution forstructural upgrades or repairs. Oursystematic approach to the analysis,load test design and execution ofstrengthening projects allow us tointegrate our engineering,manufacturing and installationcapabilities into a creative, efficient,timely and cost-effective approach.

A challenging aspect to this process isthat deficient structures are in serviceand functioning, therefore, the repairor strengthening systems must betailored to serve the intended use ofthe structure without interfering withits occupants or function.

As a result of the higher load demands,existing structures need to bereassessed and may requirestrengthening to meet heavier serviceloads. In general, structuralstrengthening may become necessarydue to code changes, seismic upgradedeficiencies that develop due toenvironmental effects such ascorrosion, changes in use that increaseservice loads, or deficiencies within thestructure caused by errors in designor construction.

A combination of techniquesThe structural upgrade of concretestructures can be achieved using oneof many different upgrading methodssuch as external or internal post-tensioning systems, span shortening,externally bonded steel, fiberreinforced polymer composites (FRP),section enlargement, or a combinationof these techniques. Strengtheningsystems must perform in a compositemanner with the existing structure in order to be effective and share theapplied loads.


For more information, please refer to the VSL Repair and Strengthening Brochure

Figueira da Foz Bridge – Portugal

Kingston Bridge – UK

Silo upgrade - USA

Haivan – Vietnam

VSL has been manufacturing anddesigning bars for the constructionindustry since 1971. VSL has an extensivelist of hot-rolled products as well ascold-rolled bars. These have proven to be one of the most popular tools of engineers wishing to induce andcontrol loads and forces in structures.

VSL’ s product line complies withinternational standards, including ISO,Eurocodes, ASTM, Australian Standards,British Standards, and such like.

A range of diameters is available to

give a wide selection of tendon forces.The prestressing force is anchored atthe end of the bar by a rolled thread,nut, washer and bearing plate.Where necessary bars can be joinedwith threaded couplers, and clevisfittings may be used where pinconnections are required.

VSL Bars systems are specificallydesigned to suit all geotechnicalapplications as well as civil works andbuilding applications. The systemsrange from High Tensile Cold WorkedStressbar to Low Tensile Architecturalbars, all with compact and easy to assemble fittings.

VSL bar systems are ideal for theeconomic application of post-tensioning forces on relatively shorttendons. Through the use ofthreaded connections andanchorages they are simple to useand lend themselves to manyapplications.

All bars and fittings must receiveprotection when installed underpermanent conditions or used in an exposed environment. One of thefollowing coating systems may beused.

• Galvanising• Greased and sheathed

in a polyethylene tube• Epoxy paint system

A combination of the above systemsmay also be specified. Considerationmust also be given to the threadedends to ensure correct installation of fittings after coating.

Typical applications

Buildings• Prestressed beams and columns• Precast connections

Bridges• Stay cable • Hangers• Temporary prestressing of segments• Strengthening• Tension piles and caissons

Wharves & jetties• Stressed deck planks• Tie backs

Anchors• Permanent and temporary

ground anchors• Uplift anchors (dam & foundation)• Roof bolting• Soil nails (slope stabilisation)• Crane bases• Light towers

Specialist Engineering• Heavy lifting• Formwork ties or hangers• Frame ties• Pile testing• Architectural ties

32

Westbound Off-Ramp to Western Arterial Road - Australia

Bar system


Hong Kong Stadium – Hong Kong Bar technology


Rock bolts• Stabilising galleries during excavations• Stabilising unstable rock/soil• Flexible attachment thanks to the high level of steel elongation/ductility• A range of different anchoring systems• Grouted, resin anchors, expansion shells• A large number of special accessories

Soil nails• Slope stabilisation• Retaining wall strengthening• Flexible attachment thanks to the high level of steel elongation/ductility,

permitting soil movement• Permanent and temporary use

Micropiles• Foundations (compressive load)• Tensile piles (tensile load)• Ideal for alternating tensile and compressive loadings• Securing of building foundation walls, embankments, compacted soil areas,

high-rise buildings, structures in seismic areas

Ground anchors• Tie-backs• Retaining walls• Stabilising deep excavations, anchoring tower cranes• Permanent and temporary use

Tie rods• Tie-backs• Retaining walls• Sea walls• Permanent and temporary use

Reinforcements• DIN 488 accreditation for B500 steel quality• Convenient for coupling through the use of continuous threading• Efficient coupling solution in areas where there are too many steel components• Alternative to shear studs

Stress bars• High performance for forces ranging from 270 to 1,320 kN• Prestressed/post-tensioned concrete structures• Strengthening of buildings• Temporary prestressing and bracing

Form ties• Same production quality level as high grade stress bars• Additional steel qualities, e.g. St 1,000/1,100 (weldable, high ductility,

suitable for low temperatures), S850/900 steel with cold-rolled thread• Accessories to suit all assembly situations

Architectural stress bars. Foot bridges. Small road bridges. Suspended roofs. Curtain walls

VSL Anchors can be divided into twomain categories — strand and baranchors. The type of anchors useddepends on whether it is for rock orsoil, for temporary or permanent use,whether or not it is to be tensioned,and whether or not permanentcorrosion protection is required.

VSL offers all of these alternatives cansupport a full anchor material supplyservice (anchors and accessories) withback-up including design services,advice, consultancy, testing,installation, tensioning, sitesupervision and monitoring. Theconstruction of the VSL strand anchordepends on the type of application(rock or soil),the design, the corrosiveness of theenvironment, the presence of strayelectrical currents and the intendedservice life. While temporary groundanchors require limited or no corrosionprotection, permanent ground anchors(with a service life exceeding two orthree years) need to provide acomprehensive permanent corrosionprotection system.

Specific requirementsAnchorages can be designed to allowthe anchor force to be adjustable,

releasable or be used as a monitoringanchor. VSL's range of anchors extendsfrom permanent anchors thatAllow electrical resistancemeasurements to be taken to checkthe integrity of the encapsulationduring the entire service life, totemporary anchors that can be easilyextracted after use. VSL also offers loadcells that allow the anchorperformance to be monitored.The anchor shown on this pagerepresents a typical permanent strandanchor with a thick walledpolyethylene encapsulation acting as a protective barrier against corrosion.Temporary anchors are similarlyconstructed except that, beingdesigned for a shorter service life,corrosion protection requirements areusually less demanding. The anchor is not normally encapsulated and cantake the form of a bundle of barestrands in contact with grout over thebond length of the anchor.

Both types of anchor systems comprisethe anchor with a bearing plate, anchorhead and wedges.

Electrically isolated anchorsThese anchors use tight PEencapsulation combined with an

electrically non-conductive anchorageisolation. The integrity of the anchorcan be checked throughout its servicelife using electrical resistancemeasurements.

Force measurementsVSL is able to provide speciallydeveloped load cells for temporary andpermanent control anchors, as well asfor permanent surveillance anchors.The following three types are available:• type G hydraulic load cell,

permanently installed for controlanchors;

• type GW hydraulic load cell, used as a removable load cell allowing severalpermanent anchors to be measuredfrom time to time by moving the cellfrom one anchor head to the other;

• type D electrical load cell, providingsupervision of permanent andtemporary anchors and allowingcontinuous load measuring usingeither a direct or remote readingsystem.

All load cell types are fully compatiblewith the VSL Anchor system.Our scope of services includesconsultancy, supply and installation ofload cells, as well as control anchorreadings.


Ground anchors

Masjed Dam – Iran The Andes – Argentina Anchor testing


Bond Lenght

Bore Hole

Spherical nutHot-Dip galvanized protective cap

O-ringH.D.P.E. smooth or corrugated boresheathing over free length

External spacers at 1500 max. centresCorrugated sheathing (Polyethylene)

CT StressbarInternal spacersat 1500 max. centres

Steel nose cone

Protective greaseSpherical washer

Hot-Dip galvanized bearing plate with trumpet

Free Lenght

Permanent VSL stressbar anchor fully encapsulated

Nitroseal PX220

Grout tube innerGrout tube outer

Corrugated shea-thing (Polyethylene)

CT Stressbar

Internal spacers

Bore hole

For more information, please refer to the VSLGround Anchors Brochure

Typical permanent strand anchor

Bond length

Free length

tightly sea-led, strongprotectivecap

corrugated poly-ethylene sheath in bond length

bare strand

grout inlet

transition fromfree length(smooth polyethylenesheath) to bond length (corrugated polyethylenesheath)

protective cap

spreader

spacer

smooth polyethylenesheath in free length

Bond Lenght

Bore Hole

Grout tube

Spacers at 1500 max.centres

CT Stressbar epoxycoated if required

H.D.P.E. smooth shea-thing over free length

Greased bar over free length

Bearing plateSpherical washer

Spherical nut

Grout

Heat shrink & sleeve

Free Lenght

Temporary VSL stressbar anchor

Anchor load checksVSL performs periodic anchor loadchecks using suitable equipment andcompetent personnel. This is carriedout by lift-off checks using VSL jacks orthe required type GW load cells.Standard load checks can be carriedout on type EG, ER and EA anchorages.With our specially developed APP jacks,we are in the unique position to carryout lift-off checks on anchors with type

EF anchorages where the anchor headhas no thread and where projectingstrands were cut after installation. Thejack has a mechanism to grip standardsize anchor heads with up to twelve 13mm (0.5") strands or seven 15 mm (0.6")strands. This allows clients to carry out

load checks in situations that, in thepast, had been particularly difficult.

Anchor extractionIt is often undesirable to leavetemporary anchors in the ground,particularly in urban areas where theynormally extend into adjacentproperty. The method developed by VSLfor extracting the free anchor length isbased on a specially designedmechanism located at the point wherethe strand is disconnected.VSL has a long tradition in this specialtechnique, with thousands of anchorssuccessfully extracted.VSL offers also temporary stressbaranchors wich permit partial extraction.

Grout tube

SpacersCT StressbarBore hole

Heat shrink

polyethylenecoated and greased strand with tensile / yieldstrength acc.to local requirements

development of passive resistance onthe projected area of the meshcrossbars, which in turn transfers loadinto the longitudinal bars.In the case of polymeric stripreinforcement, load transfer from the

The VSoL® retained earth system is acomposite soil reinforcing system thatuses welded wire mesh or polymericstrips to resist the horizontal forcesgenerated within an earth backfill.A retained earth structure is a stable,unified gravity mass that can bedesigned for use in a wide range of civilengineering applications. The VSoL®system is widely used and accepted asa major construction method inprojects ranging from retaining wallsto highway bridge abutments.The basic retained earth principleinvolves transferring stresses from the soil to the reinforcing elements.In the case of welded wire mesh soilreinforcement, this is achieved by the

backfill is achieved by the frictionalinteraction of the soil particles with the polymeric reinforcing strip.In addition to its high performancelevel, the VSoL® system ensureseconomical design and construction.The system requires only threecomponents: reinforcing elements,precast facing panels and backfillmaterial. This simplicity results in easyand rapid construction. Cost savings of up to 50% below those of traditionalretaining wall systems are regularlyachieved.

Fast, easy and economicalThe construction of a VSoL® structureis particularly straightforward.


VSoL®

Nundah bypass – Australia

Penny’s Bay – Hong Kong

Perspective ViewVSoL® retained earthRetaining Wall

A five-man crew using standardconstruction equipment can place an average of 75 m2 - and as much as140 m2 - of wall per shift.

Complete servicesVSL advises customers and theirconsulting engineers during thefeasibility stages of projects, and

prepares preliminary design and costestimates, as well as detailed designs,drawings and specifications.The company also assists contractorswith the pricing of tenders,and provides quotations during tenderstages. Execution of the on-site projectcan be tailored to suit the customers’requirements, from a supply onlyarrangement to a full sub-contractagreement.

Complete flexibilityVSoL® system concrete facing panelsare available in a wide range of shapes,textures and colours. Because localmaterials are used in the production of these precast panels, the visibleexposed surface can easily be colouredto match the natural surroundings.Raised relief, sandblasted finish,exposed aggregate, and conventionalsmooth face concrete represent justa few of the available standardretained earth panel finishes.Other facing systems, such as modularblocks, and mesh are also available for both permanent and temporarystructures.


La Polvora – Chile

Typical SectionVSoL® retained earth Wallat a Bridge Abutment

For more information, please refer to the VSoL® Brochure

Ultrera – Spain

Truckroad – Dubai

Castel Peak Site – Hong Kong

Ductal® is a material with a uniquecombination of superiorcharacteristics.

The material was developed byBouygues in partnership with Lafargeand Rhodia under the generic name of Reactive Powder Concrete and ismarketed under the brand name ofDuctal®. Composed of fine particleswith a maximum size less than 0.8mm,Ductal reaches compressive strengthsof 170 to 230 MPa.

In structural applications, Ductal® is used without any passive reinforcingbars. Very fine, high strength steelfibres are provided to withstandsecondary tensile stresses due to shear,tension, small bending moments andconcentrated loads. Pre-or post-tensioning counterbalances the maintensile stresses due to large bendingmoments. The steel fibres also providesignificant ductility to thecementitious paste.

In non-structural applications, Ductal®is used with non-metalic fibres. Passivesteel reinforcement and prestressingare not required. Ductal® has theability to replicate the micro and nano-texture of the mould. Whencombined with the fluidity and theability to have a range of colours, theresult is a material that provides a high

quality surface appearance togetherwith high strength and durability.

The durability properties are those of an impermeable material. There is almost no risk of carbonation or

38

Ductal®


Sakata Mirai – Japan

Seonyu – Korea

penetration of chlorides and sulfides,and the resistance to acids is improved.

Main advantages• Eliminates completely the need for

conventional reinforcement• Greatly improves durability, with a

resistance to permeability 50 timesbetter than normal high strengthconcrete

• Permits the use of much thinnersections

• Provides complete freedom on theshape of the section

• Reduces the concrete volume of astructural member to only one thirdto one half of its conventional volume

• Dramatically reduces the structuralweight to be supported by a structure

• Provides both direct and indirect costsavings.


Strength characteristics (steel fiber reinforced)• Compressive strength (cylinder) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170-230MPa• Flexural strength (3 point bending test) . . . . . . . . . . . . . . . . . . . . . . . . . . 40-50 MPa• Youngs modulus(E). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50-60 GPa• Total fracture energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20,000-30,000 J/m2

Rheology• Fluid to self compacting• Flow (Abrams cone) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50-70cm• Flow (ASTM shock table) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250mm

Durability• Chloride ion diffusion (CI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12 m2/s•Carbonation penetration depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <0.5mm•Freeze/thaw (after 300 cycles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100%•Salt-scaling (loss of residue). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <10g/m•Abrasion (relative volume loss index) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2

Other properties• Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2450-2550 kg/m3

• Entrapped air content. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4%• Freeze/thaw (after 300 cycles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100%• Total porosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6%• Shrinkage after heat treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0• Creep coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2-0.5

Reina Sofia – Spain

Typical applications

Bridges• Beams• Truss type structures• Decks of steel bridges

Buildings• Beams• Slabs• Permanent floor formwork• Curtain wall panels• Facade panels• Columns• False floor panels• Grandstand seating plats

Railways• Sleepers• Sound absorbing panels • Noise walls

Highways• Light poles• Crash barriers• Noise walls

Civil• Pipes• Hazardous waste

containment• Arch culverts

Other• Blast protection• Vaults

Ductal® blast – Australia

Generally, structural bearingsare required to connect different partsof a given structure, such as a bridgedeck to piers and abutments. The mostwidely used structural bearings arereinforced elastomeric bearings andpot bearings. They are capable of

transmitting forces while absorbingthe structures deformations androtations.The strength of reinforced elastomericbearings is limited by the shearproperties of the elastomeric block,especially when compression, shearand bending occur at the same time.Pot bearings maximise the shearstrength of the bearings elastomer by encasing it in a steel cylinder.Elastomeric and Pot bearings can befixed, guided or free depending ondesign requirements

VSL offers fixed pot-bearings which permit movement in one or any direction.Pot bearings for incrementallylaunched bridges have a dual function.First, they provide low friction slidingsurfaces over piers as the deck ispushed during construction. Thereafter,they become permanent bearings. Apot bearing serving these functions isshown in the picture above. Duringconstruction, a fixing device avoidsrelative movement between the slidingplate and the pot cylinder.


Bearings

Stainless steel

Lubricant

P.T.F.E.

DU-metal

External Sealing Ring

Piston

Internal Sealing Ring

Elastomer Pad

Pot (Steel Ring + Base Plate)

Anchor Sockets

Guide

Top plate

Pot bearing for incrementally launched bridges

Pot bearing Type PU

Pot bearing under fabrication

The sliding plate is equipped with anupper stainless steel panel.This is followed by the insertion ofneoprene-teflon pads during thelaunching operation to be carried out.The pads, upper stainless steel paneland fixing device are removed afterlaunching. Finally, the sliding plate isconnected to a previously embedded steel plate in the deck.

Bearing on pier

For more information, please refer to VSL Potbearings and Elastomeric bearings brochures

Single element steel expansion jointsUsed in building, pedestrian andvehicular structures to seal the gapbetween two structures so that theycan move independently withoutadversely affecting each other. Thejoints are of either aluminium or steelwith a flexible seal spanning betweenthem and can accommodate movementranges between 15 mm to 40 mm.

Multi element steel expansion jointsUsed in highway and bridge structureswith large movements due to theeffects of concrete shrinkage, thermaland seismic effects or differentialsettlement and ground movements.Typical movement ranges from 65 mmper single seal upto 1 m whenconnected together. VSL services usingmultiple elements include design,supply, 1st installation and long termmaintenance.

Elastomeric expansion jointsElastomeric expansion joints havebeen designed to work as a singleelement, to be absolutely tight

and long-lasting. These joints allowhorizontal, vertical and obliquemovements, remaining tight.The elastomeric material properties are such that the bearings are notaffected by low temperatures.Capability of impact absorption is keptduring winter. The characteristics of this materialal also allows resistanceto wearing and abrasion and resistance against bad weatherconditions, chemical products and fire Typical movement ranges from 40 mmup to 330 mm.


Expansion joints

Joints – Chile

Multi element Single element

Monitoring should be a simple andeconomic activity, adapted to each ofthe specific parts of the structuredepending on functional and riskanalysis. VSL’s monitoring package isoffered as an additional service toprovide the client with longterm costsavings. It can be applied to structuresand to cables (bridges, buildings) eitheras ground anchors, post-tensioningtendons, or stay cables.In-house R&D has placed emphasis ondurability method, measurement andsensor configurations, thus allowing toboth assess the actual condition ofstay cable system components andpredict subsequent evolution. The VSLfull service monitoring package may beused to assess shrinkage, stress

evolution and vibration of the concretestructure weather conditions, traffic,pollution; to send and to follow-up thebehavior of the structure, optimisemaintenance; to detect damage andconfirm diagnosis of deterioration; tovalidate and memorise know-how forfuture projects; to optimise life cyclecost of the structure.As an additional service, the VSLDeMon system allows wirelessconnection from your office to any typeof sensors on site through internet andwireless devices. The system providesreal time, 24 hours a day, filtering of the data to detect events, to send an alarm and to analyse onlysignificant events.


Structural monitoring

Wind speed measured in 3 directions expressed in m/s

Temperature of cables, concrete

expressed in °C

Humidity expressed in %

Rain intensityexpressed in mm

Air qualityexpressed in CO, NOX, O3, SO2...

Structural vibrationacceleration expressed in gvibration modes expressed in Hz

Angular movement two directions expressed in °

°°

Stress and deformation expressed in μm/m and in mm

Inspection and investigationpaper and multimedia reports laboratory or in situ tests

Traffic expressed in km/h, veh./h, t, type...

Cable forceexpressed in kN

Sun intensity expressed in W/m2

Material ageing expressed in Cl-, mV…

OPERATING COST MAINTENANCE COST

www.vsl-monitoring.c

om

Relevant information is sent

straight back to the user’s desk.

The system works with any IT

and measurement solution.

°°

The Consultant

VSL

Remote server

The Owner

MYBRIDGE

VSL load cell

C R E AT I N G S O L U T I O N S T O G E T H E Rwww.vsl-intl.com

THAILANDVSL (Thailand) Co. Ltd.BANGKOKPhone: +66 - 2 - 237 32 88 / 89 / 90Fax: +66 - 2 - 238 24 48

VIETNAMVSL Vietnam Ltd.HANOIPhone: +84 - 4 - 8245 488Fax: +84 - 4 - 8245 717

Ho Chi Minh CityPhone: +84 - 8 - 8106 817Fax: +84 - 8 - 9102 596

Australia

VSL Australia Pty. Ltd.SYDNEYPhone: +61 2 9 484 59 44Fax: +61 2 9 875 3894

BRISBANEPhone: +61 7 3265 64 00Fax: +61 7 3265 75 34

MELBOURNE and SOUTHERNPhone: +61 3 979 503 66Fax: +61 3 979 505 47

Americas

ARGENTINAVSL Sistemas Especiales deConstrucción Argentina SABUENOS AIRESPhone: +54 - 11 - 4326 - 06 09Fax: +54 - 11 - 4326 - 26 50

CHILEVSL Sistemas Especiales deConstrucción S.A.SANTIAGOPhone: +56 - 2 - 233 10 81Fax: +56 - 2 - 233 67 39

COLOMBIASistemas Especiales de Construcción Ltda.BOGOTAPhone: +57-1-633 21 09Fax: +57-1-633 21 09

MEXICOVSL Corporation Mexico S.A de C.VMEXICOPhone: +52 - 5 - 396 86 21Fax: +52 - 5 - 396 84 88

UNITED STATESVStructural LLCBALTIMORE, MDPhone: +1 - 410 - 850 - 7000Fax: +1 - 410 - 850 - 4111

VENEZUELAGestión de Obras y Construcciones C.A.CARACASPhone: +58 - 212 941 86 75Fax: +58 - 212 941 86 75

Middle East

UNITED ARAB EMIRATESVSL Middle East LLCDUBAI, UAEPhone: +971 - 4 - 296 63 99Fax: +971 - 4 - 296 65 52

Africa

EGYPTMatrix Engineering CompanyCAIROPhone: +20 - 2 - 344 19 00Fax: +20 - 2 - 346 04 57

MOROCCORenfor-BatTANGIERPhone: +212 - 39 - 95 80 87Fax: +971 - 39 - 95 80 85

SOUTH AFRICATsala-RMS Construction Solutions (Pty) LtdJohannesburgPhone: +27 11 878 - 6820Fax: +27 11 878 - 6821

Europe

AUSTRIAGrund-Pfahl- und Sonderbau GmbHHIMBERGPhone: +43 - 2235 87 777Fax: +43 - 2235 86 561

BELGIUMN.V. Procedes VSL SABERCHEMPhone: +32 3 230 36 34Fax: +32 3 230 89 65

CZECH REPUBLICVSL Systemy (CZ), s. r. o.PRAGUEPhone: +420 - 2 - 67 07 24 20Fax: +420 - 2 - 67 07 24 06

FRANCEVSL France S.A.TOULOUSEPhone: +33 (0)5 61 00 96 25Fax: +33 (0)5 61 00 96 51

GERMANYVSL Systems GmbHBERLINPhone: +49 30 53 01 35 32Fax: +49 30 53 01 35 34

GREAT BRITAINVSL Systems (UK) Ltd.BEDFORDSHIREPhone: +44 (0) 1480 404 401Fax: +44 (0) 1480 404 402

NETHERLANDSVSL Benelux B.V.OEGSTGEESTPhone: +31 - 71 - 576 89 00Fax: +31 - 71 - 572 08 86

NORWAYVSL Norge A/SSTAVANGERPhone : +47 - 51 58 81 25Fax : +47 - 51 58 81 26

PORTUGALVSL Sistemas Portugal Pre-Esforço, Equipamento e Montagens S.A.S. DOMINGOS DE RANAPhone: +351 - 21 - 445 83 10Fax: +351 - 21 - 444 63 77

VSL GEOSistemas de Aplicação em Geotecnia SAS. DOMINGOS DE RANAPhone: + 351 - 21 - 445 83 10Fax: + 351 - 21 - 445 83 28

Asia

BRUNEI VSL Systems (B) Sdn. Bhd.BRUNEI DARUSSALAMPhone: +673 - 2 - 380 153 / 381 827Fax: +673 - 2 - 381 954

HONG KONGVSL Hong Kong Ltd.WANCHAIPhone: +852 - 2590 22 88Fax: +852 - 2590 02 90

Intrafor Hong Kong Ltd.WANCHAIPhone: +852 - 2836 31 12Fax: +852 - 2591 61 39

PT Laboratories Ltd.KOWLOON BAYPhone: +852 - 2758 48 61Fax: +852 - 2758 89 62

INDIAVSL India PVT Ltd.CHENNAIPhone: +91 - 44 4225 11 11Fax: +91 - 44 4225 10 10

INDONESIAPT VSL IndonesiaJAKARTAPhone: +62 - 21 - 570 07 86Fax: +62 - 21 - 573 12 17

JAPANVSL Japan CorporationTOKYOPhone: +81 - 3 - 3346 - 8913Fax: +81 - 3 - 3345 - 9153

KOREAVSL Korea Co. Ltd.SEOULPhone: +82 - 2 - 553 8200Fax: +82 - 2 - 553 8255

MAINLAND CHINAVSL Engineering Corp., Ltd.HEFEIPhone: +86 551 3822918Fax: +86 551 3822878

MALAYSIAVSL Engineers (M) Sdn. Bhd.KUALA LUMPURPhone: +603 - 7981 47 42Fax: +603 - 7981 84 22

PHILIPPINESVSL Philippines Inc.PASIG CITYPhone: +632 672 17 03Fax: +632 672 13 95

SINGAPOREVSL Singapore Pte. Ltd.SINGAPOREPhone: +65 - 6559 12 22Fax: +65 - 6257 77 51

TAIWANVSL Taiwan Ltd.TAIPEIPhone: +886 - 2 - 2759 6819Fax: +886 - 2 - 2759 6821

SPAINCTT StrongholdBARCELONAPhone: +34 - 93 - 289 23 30Fax: +34 - 93 - 289 23 31

VSL-SPAM, S.A.BARCELONAPhone: +34 93 846 70 07Fax: +34 93 846 51 97

SWEDENInternordisk Spännarmering ABVÄSTERHANINGEPhone: +46 - 8 - 5007 3820Fax: +46 - 8 - 753 49 73

SWITZERLANDVSL (Switzerland) Ltd.SUBINGENPhone: +41 - 32 613 30 30Fax: +41 - 32 613 30 15

VSL (Suisse) SAVOUVRYPhone: +41 24 48157 71Fax: +41 24 48157 72

HEADQUARTERS

VSL International Ltd.

Scheibenstrasse 70 – Bern

CH-3014 – Switzerland

Phone: +41 32 613 30 30

Fax: +41 32 613 30 55 VSL LOCATIONS

Copyright 2006, VSL International Ltd.Printed in France - patented

The information set forth in this brochureincluding technical and engineering data ispresented for general information only. Whileevery effort has been made to insure itsaccuracy, this information should not be used orrelied upon for any specific application withoutindependent professional examination andverification of its accuracy, suitability andapplicability. Anyone using this material assumesany and all liability resulting from such use. VSLdisclaims any and all express or impliedwarranties of merchantability fitness for anygeneral or particular purpose or freedom frominfringement of any patent, trademark, orcopyright in regard to the information or productscontained or referred to herein. Nothing hereincontained shall be construed as granting alicense, express or implied under any patents.

Documents

VSL Construction systems - FenixEdualfaiate/rma/Construction_systems_2006... · VSL CONSTRUCTION SYSTEMS Post-tensioning Stay Cables Heavy Lifting ... Indonesia Penny’s Bay Viaducts