Special ReportPrecast Bridge DeckDesign SystemsbyMrinmay BiswasProfessor of Civil Engineering, andDirector, Transportation and InfrastructureResearch CenterAssociateDuke UniversityDurham, North Carolinahe use of precast concrete for newTbridge construction and for the reha-bilitation of deteriorated bridges is economically and structurally amenable totoday's systems engineering concepts. 1.2 3 Precast elements can be usedfor pedestrian, highway and railwaybridges. They can be adapted to alltypes of structures having short,medium and long spans.Precast products can be used for someor most of the components of a bridge'ssuperstructure and/or substructure.Durability, ease and speed of construction together with reduced need formaintenance are all advantages in usingprecast concrete.Depending on the span length andtype of application, a precast elementcan be prestressed or nonprestressed,The largest precast elements used inbridges are prestressed box girder segments. Precast prestressed segmentalconstruction started in Europe in 1948as an efficient and economical means ofreplacing the bridges destroyed duringWorld War 11.Segmental construction with its manyramifications was introduced to North40America in the early seventies and during the last decade the technologygained from the numerous applicationsof the method has grown enormously.Spans ranging from 150 to 800 ft (46 to244 m) can be efficiently built usingsegmental construction. When combined with a cable-stay system, the economical span can extend to at least 130011 (396 in).The evolution of prestressed segmental bridge construction throughoutthe world is well documented'-' 2 Thiswide application has also motivated research and development. Results ofsome of the tests and a review of specificdesign problems have recently been reported.'The AASHTO-PCI standard I girdersections are some of the largest precastelements used in bridge construction.Spans up to 150 ft (46 in) can be readilydesigned using these sections. Theirintroduction in the fifties sparked effortsto standardize design.Based on these early sections, severalstates have developed their own standards. Subsequent modifications tothese standards continue to be devel14

This report describes applications of full depth,precast concrete panels for the rehabilitation ofdeteriorated bridge decks and the construction of newbridges. Emphasis is placed on systems ofconstruction and the economy derived in using precastconcrete for bridge construction.The report presents design systems, details of jointsand joint material used for a number of highway andrailway bridges. The advantages and a few of thedifficulties involved in this construction method arediscussed including some pertinent research work.oped.',15 The current availability of highstrength concrete provides further incentive for modifications. In some cases,these standard sections can be stretchedto accommodate special long span applications.'Precast I girders are used in conjunction with cast-in-place deck, stay-inplace metal forms, or stay-in-place precast concrete deck panels. Concretestay-in-place deck panels are a significant precast element in bridge superstructures. Concrete deck panels canalso be used with steel girders orstringers. In this capacity they are usedfor both new bridge construction andbridge deck rehabilitation.The introduction of deck panels followed extensive research both in thelaboratory and in the field. The currentAASHTO Bridge Specifications cover theanalysis, design and fabrication of deckpanels." The results from research andsuccessful applications of deck panels arewell documented.Integrally constructed girder cued deckcomponents are another type of important precast prestressed concrete element for bridge construction. TypicalPCI JOURNALJMarch-April 1986sections are shown in Fig. 1. These sections are suited for short span highwaybridges because of their low cost andrapid erection?s-"Solid and voided slabs can be used forspans of 35 and 50 ft (11 and 15 m), respectively.Channel or multiple stemmed sections with cast-in-place decks can beused to span up to about 70 ft (21 m).Single-stemmed sections and boxbeams can be used to span up to about120 ft (37 m). The box beams may beused either as adjacent units or spacedapart.Bulb tees, which incorporate featuresof the AASHTO-PCI I girders andsingle-stemmed sections can bedesigned to span up to about 180 ft(59 m).The integral sections, especially thesingle and double box beam and thedouble-stemmed sections are particularly suitable for railway applications.These sections have been used to replace old timber trestles with speed andeconomy.Full span, stay-in-place deck formsare another element with growing ap41

plications in bridge construction. Research results of laboratory tests on suchsystems are given in Ref. 29.A need to rehabilitate the nation's infrastructure system is now widely recognized. An enormous number ofbridges are either functionally obsoleteor structurally deficient. The deck portion of a bridge superstructure is particularly vulnerable to deterioration.Traffic, weather, and chemicals used forice control" all work to destroy a bridge,Extensive deck deterioration is common in many bridges over 25 years old.Even in many newer structures deckdeterioration is becoming increasinglyevident.Local patching and overlaying can beused as short-term repair methods dur-ing the early phases of deterioration.Eventually, total replacement of thedeck is required. This is illustrated inFig. 2.Cast-in-place concrete deck is oftenused as a replacement deck. Thismethod of construction, however, isvery slow and labor intensive. Inclement weather and other on-site problems make quality control of concreteand other operations difficult. The ensuing result can be either a substandardrepair job or a delay in completing theproject.A combined precast panel subdeckand cast-in-place top deck has becomeincreasingly common today. The materials and methods used in this type ofconstruction are similar to those of con-BOXOptional C.i.PTopping (TYP)CHANNELSINGLE TEEoo 000 oao 000VOIDED SLABFig. 1. Typical integral precast deck sections.42

oy DECK REPLACEMENTmrru-—PROTECTION, REPAIR,AND MAINTENANCEQU25%% OF BRIDGE DECK DETERIORATIONFig. 2. Economics of bridge deck repair and rehabilitationventional concrete construction (seeFig. 3) except that the cost of formworkis eliminated.NEED FORPRECAST CONCRETEWith urban expansion, traffic densityon and around most bridges has increased dramatically. One very impor-tant criterion in selecting a deck rehabilitation system is that it must minimizeinterference with local traffic. Rapidconstruction using modular full depth,precast deck elements is particularlysuitable in meeting such a requirement.Fig. 4 schematically illustrates a methodwhere old cast-in-place deck is segmentally removed and replaced by fulldepth deck elements.For short span structures, integralCAST-IN- PLACEREINFORCED CONCRETEPRECAST CONCRETEPANELFig. 3. Partial depth precast panel subdeck.PCI JOURNAL/March -April 198643

New Full -depthPrecast PanelsExistingStringersDeterioratedExisting DeckFig. 4. Full depth precast panel application.deck systems can be economically usedto replace both deck and stringers simultaneously. For bridges where the decksupporting structure, i.e., the stringersor girders, are in good condition, onlythe deck portion may need to be replaced by precast elements.Precast elements can provide an additional advantage of greater durabilityover cast-in-place concrete. Better quality control of material in a precast plantcan result in higher strength concrete.One important point to remember is thatprecast concrete becomes increasinglyeconomical with repetitive elements.However, certain special constraintsrelated to the use of precast concreteshould be recognized. The examplebelow illustrates such a case.Fig. 5 shows the plan, elevation andcross section of a bridge which is not44level and square. The roadway is onboth a vertical and horizontal curve. Thespans have superelevation and skew.The old stringers may have partiallength riveted cover plates. When a precast system is chosen, special fabricationand construction procedures should befollowed to ensure that the precast elements achieve proper fit.When an existing structure is composite, the replacement structure mustalso be composite. Even when an existing structure is not composite, becauseof greater load carrying capacity requirements and larger roadway widthrequirements of many rehabilitationprojects, the replacement structures areoften required to be composite.Fig. 6 shows the basic load transferrequirements for a composite structureusing precast elements. Figs. 6(a) and

0.PLANELEVATION40 FtTRANSVERSE SECTIONFig. 5. Plan, elevation and transverse section of a complex steelI girder bridge.6(b) show the vertical load transfer andhorizontal shear transfer, respectively,at the interface of the deck slab andstringer. Figs. 6(c) and 6(d) show thehorizontal in-plane forces and verticalshear transfer at the interface of adjacentdeck slab panels.A proper design must adequately address the following three criteria: (1)PCI JOURNALJMarch -April 1986tactical requirements related toschedule and traffic interference, (2)geometric fitup problems and (3) loadtransfer, strength and serviceability requirements. The design, of course, mustalso meet the project's overall modular construction, the performance of joints is especially critical45

rnVertical Normcl Forces(a)H orizontal Shear Forces(b)Deck Slab.aHorizontal Normal Forces(c)Fig. 6. Load transfer mechanisms of composite deck.Vertical Deflection(d)

for the integrity of a structural system.The geometric configuration of a joint,in addition to the selection of an appropriate interface material contribute tothe proper short-term and long-termperformance of the structure.With these criteria and requirementsin mind, this report examines the detailsof structural systems, precast elements,joint configurations and joint materialsfor full depth, precast concrete paneldecks and a number of bridge rehabilitation projects.APPLICATIONSPRIOR TO 1973Several bridge decks were constructed using fill depth, precast panelsprior to 1973. 1 ' The construction of thetwo-lane Pintala Creek Bridge in Montgomery County, Alabama, is one of theearliest examples of full depth precastconcrete panels used for bridge deckconstruction. This bridge is composed offour 34 ft (10 m) long spans.Full depth and full width precastpanels 6'/2 in. (165 mm) thick, 7 ft (2 m)long and 26 ft (8 m) wide, complete withcurbs, were placed uniformly over thestringers. A I ft 6 in. (0.46 m) space wasleft between adjacent panels. Theinter-panel space was filled with castin-place concrete (see Fig. 7).When the Kosciuszko Bridge, Brooklyn-Queens Expressway, New York, wasunder reconstruction in 1971, full depth,full width precast panels were used tobuild a temporary trestle to detour theexpressway traffic which includedheavy trucks. The details of this construction are shown in Fig. 8. The combined curb and railings used in thisproject were also precast modules,bolted to the deck slab.Based on research performed at Purdue University,n2 in 1970 the IndianaState Highway Commission sponsoredtwo projects in order to utilize full depthprecast panels. One involved new conPCI JOURNAUMarch-April 1986struction and the other a rehabilitationjob. Superior quality control and the resulting excellent durability of precastconcrete were the primary motivationsfor these projects."The newly constructed structure wasthe Big Blue River Bridge over IndianaState Road 140 near Knightstown. The200 ft (61 m) long structure had steel Ibeam girders at 6 ft (1.8 m) on centers,continuous over three spans, 70, 60, and70 ft (21, 18 and 21 m) long, respectively. Full width panels were typically4ft(1.2 in) long and 39ft(12m)wide.Panels were transversely pretensionedand the deck was nominally posttensioned in the longitudinal direction.A similar method was used to replacethe deteriorated decks of the then 30year-old Bean Blossom Creek Bridge onIndiana State Road 37, near Bloomington. The existing structure was aneight-panel through type Pony truss,each about 125 ft (38 m) long. In bothstructures, no overlay was used, and thetop of the precast slabs served as theriding surface. The structures were instrumented and their performance wasmonitored. Scholer recently reportedtheir periormance to be quite satisfactory.33Applications of full depth precastpanels in bridge deck construction priorto 1973 can he summarized as follows.The deck-stringer systems were primarily noncomposite, although incidentaldevelopment of composite action wasreported. The spans did not have anyskew or superelevation. More projectsinvolved new construction rather thanrehabilitation, Fewer geometric fitupproblems were experienced with newconstructions than with replacementdecks. The method was used for bothpermanent and temporary construction.Those structures in general have performed very well. Minor problems weremainly due to the partial failure of joints,especially at slab-to-slab interfaces.Two structures merit separate mention. These are: (1) the Hannover47

34-0 cont.7L O"(TypE -6 (TypJCast in Place,--PrecastLONGITUDINAL SECTIONIiiSCast in PlaceConcrete1/2110 SaltW 21xTRANSVERSE SECTIONFig. 7. Pintala Creek Bridge, Montgomery County Commission, Alabama.Curved Viaduct Ramp (Fig. 9); and (2)the Emil-Schulz Bridge (Fig. 10). Thesewere major spans, both built in Germany, using precast decks on steel boxgirders, They were both composite.Epoxy mortar was used as the joint material along with high strength bolts asshear connectors.34The designs used and the experience48gained in the applications prior to 1973provided the knowledge base for futuredevelopments.1973 AND AFTERSignificant advances have been madesince 1973 with the construction ofmajor bridges, some over 1000 ft (305 m)

VariesMax.-0' Min./4II(Typ.)PrecastLONGITUDINAL SECTION'/4 ' ( T}4RichmondInsertPrecast SlabI ' @ Pierl'iairBeni I -./B x 6x I s3/41 BOILTRANSVERSE SECTIONFig. 8. Kosciuszko Bridge, Brooklyn-Queens Expressway, New York.long. Many of the spans are compositewhile some are continuous. A fewof the designs involved complex geometries.The details of the interfaces are thekey to precast slab stringer design. Specifically, there are three locations of interface: (1) the bedding plane at the slabto stringer; (2) the shear connectorpocket area; and (3) the slab-to-slabPCI JOURNAL/March-April 1986joint. The major emphasis of this reportis in addressing these interface details ofbridges completed since 1973.The details used in a bridge designdepend mainly on the respective transportation agency and the consulting engineer involved. Such details reflecttheir standard practice, previous experience and design philosophy. The following information is presented in a49

16.7'Box GirderPrecast Deck65TRANSVERSE SECTION-. . .-.iIsIIIII.High Strength BoltsEpoxy 'Mortar)Box Girder FlangeDETAIL AT AFig. 9. Hannover Viaduct, Germany.fairly chronological order, groupedunder the headings of specific transportation agenices.New York State ThruwayAuthority (NYSTA)In 1973, NYSTA initiated a researchand development program which included construction of a prototypebridge at the Harriman Interchange.This structure has all the complex attributes of the bridge shown in F'ig. 5.With this concept in mind, a feasibility study was undertaken of the bridgewith emphasis on design details andconstruction procedures related to theslab-on-steel stringer system 3 i ss, " Todate, three bridges have been renovatedusing these methods.Some of the features common toall three bridges are as follows: Thebridges have a composite deck systemcarrying HS20-44 type loading. Replacement precast deck panels wereconventionally reinforced. Low modulus 100 percent solids epoxy mixedwith bag sand was used as mortar. Typically, one part epoxy to two parts sandprovided a flowable mix for use at thepanel joints. Proportions of 1:2.5 gave atrowellable mix which was placed at the

iQ SymmTRANSVERSE SECTION/f -Opening in Precast SlabI!Shear Studsand SpiralsrPrecost Deckopo000Box SectionFlange FP IPLANSFC'TIfNDETAIL AT AFig. 10. Emil-Schulz Bridge, of the steel stringers and at the shearpockets.Fig. 11 shows the configuration of thepanel-to-panel joints. An oblong funnelwas needed to place flowable epoxymortar in the joint. The use of adhesivetape at the bottom opening of the jointwas not effective in containing theepoxy mortar. The opening subsequently had to be blocked by additionalformwork. Existing composite deck andspiral shear connectors had to be removed which proved to he a laboriousPCI JOURNALJMarch-April 1986and time consuming task.Some of the distinctive features ofeach of the NYSTA projects are described below:Amsterdam Interchange Bridge(1973)—Fig. 12 shows a view of thetwo-lane bridge consisting of four simple spans: 33, 59, 66 and 60 ft (1O 18, 20and 18 m) long, respectively. Thisbridge was designed to carry about 2000AADT over the mainline Thruway. Thedeteriorated deck of one-half of the 66 ft(20.1 m) span was replaced by using51

precast panels on an experimental basis.Fabrication of the precast panels andall other construction work was doneentirely by the NYSTA maintenancedepartment personnel. No contract waslet to any outside agency.A staged construction sequence wasused to maintain at least one lane oftraffic open although very brief interruptions of traffic were allowed duringthe actual placement of each precastelement.The overall width of the deck is 45 ft(13.7 m). Full depth panels measured 8JointDeck SlabNEpoxy MortarIIG ,Adhesive TapeL /Backed by LumberFig. 11. Transverse joint between precast slabs, New York State ThruwayAuthority (NYSTA).riFig. 12. Amsterdam Interchange Bridge (NYSTA).52

0 21O141 -—OilkE7 1I1101}YLStringerE: fiETemporarySpring ClipL4IPLANEpoxy MortarDeck Slab' 'Stringer —'x AC5x 94. .sa:6 'a.'dI6Joint Type F-FEpoxy MortarEpoxy MortarFig. 13. Plan and section of welded channel shear connection (NYSTA).in. (203 mm) x 4 x 22 ft (1.2 x 6.7 m). partment personnel without difficulty.They were designed to cover one-halfA "dry" system detail using long highthe width of the bridge,strength bolts was also used on a fewCast-in-place concrete was used down panels on the same span. Field applicathe centerline of the bridge which has a tion of torque for these large high6 ft (1.8 m) wide flush median mall. Figs. strength bolts was difficult. Plan and13 and 14 show the details of the bed- section diagrams of these bolted conding area and the shear pockets. Fig. 15 nections are shown in Figs. 16 arid 17.shows the casting of epoxy mortar in the The gap between the bottom of the preshear pockets. Field welded standard cast slab and the top of the stringer rechannel sections were used as shear quired shims. Achievement of full tenconnectors. These were installed by de- sion in the bolts could not be fullyPCI JOURNAUMarch-April 198653

Asphalt Wearing Surface--'IrC5/- Epoxy MortarS.IFJ/IK bDeck SlabTemporarySpring ClipEpoxy MortarShim WashersAs Req'd. (Typ.)C StringerSECTION B-BFig. 14. Detail of welded channel in shear pocket (NYSTA)Fig. 15. Casting of epoxy mortar in shear pocket (NYSTA).54

ascertained, Possible breakage of slabsbecause of excessive motion due to tensioning was also feared. For these reasons, bolted connections were not usedin subsequent NYSTA projects.NYSTA protective system of a sheetmembrane overlaid with asphalt concrete was applied on the rehabilitateddeck.Because of the attached importance ofthe Amsterdam Interchange Bridge rehabilitation scheme, the constructionwas highly supervised by professionaland management level personnel fromthe NYSTA, the consulting engineersand the epoxy supplier. The bridge hasperformed very well over the periodsince rehabilitation. Close field inspection resulting in better quality controlmay be credited as an important ingredient for this success.Krum Kill Road Bridge (1977)—Thisis a 50 ft (15 m) long single span, six-lanemainline throughway bridge carrying a3/4 ' l 9H.S.B4ringersTempeSpringr LP4 Nnark ClrthStrirsherfiredFig. 16. Plan and section of bolted connection (NYSTA).PCI JOURNAL/March-April 198655

Asphalt Wearing Surface s 1/2 11 x 3'' x 9 'IDeck Slab —- Iiitr adtt!IP,Epoxy MortarLevelling GroutShim WasherAs RequiredField Drilled HolesFor 3/a" H.S. Bolts(Interference—Body)Q StringerSECTION B-BFig. 17, Detail of bolted connection (NYSTA).Asphalt WearWaterproof MereFig. 18. Detail of welded studs in shear pocket (NYSTA).56E.S.ds

AADT 22000 over Krum Kill Road nearAlbany. Figs. 18 and 19 show the planand section details of the joints. Thesedetails are similar to the AmsterdamInterchange Bridge, except that standard welded shear studs were used instead of channel sections.The precast slab panel work includingdelivery and installation, was contracted. The balance of the work wascompleted by the NYSTA. The spans areslightly skewed but level. There are twostructurally separate spans supported oncommon abutments. Each structure carries two active traffic lanes and one inactive lane for future use. The latter wasused effectively to detour traffic duringconstruction.Precast panels, 7V2 in. (190 mm) thickand 5 ft 2 in. (1.6 m) long, of two different widths were used. For each structure, 42 ft (13 in) wide panels wereringerPLANf* - - i .i:Epoxy MortarDeck SloblieK6" Stud5w-isEpoxy MortarSECTION A-AFig. 19. Plan and section of welded stud connection (NYSTA).PCI JOURNALIMarch-April 198657

Fig. 20. Placement of 42 ft (13 m) wide panel, Krum Kill Road Bridge, NYSTA.Fig. 21, Placement of 21 It (6 m) wide panel, and longitudinal joint, Krum Kill RoadBridge.58

Fig. 22. Harriman Interchange Ramp Bridge, NYSTA.placed over six stringers and 21 ft (6.5 m)wide panels were placed over threestringers. A 3 11 (0.91 m) wide longitudinal joint at the crown line was cast inplace over continuity reinforcing barsextending from two adjacent panels.Fig. 20 shows the placement of 42 II (13m) wide panels. Fig. 21 shows theplacement of 21 ft (6.4 m) wide panelsand the longitudinal joint.During construction, cracks over thereinforcing bars were detected in theprecast panels. The cracks were treatedwith a penetrating epoxy sealer. Durability of the deck has not been affectedany further 3 7 The performance of thebridge has been satisfactory althoughseveral joints have shown signs of leakage where construction debris wasfound in the keyway. This problem indicates the need for a thorough inspection of all joints prior to placing epoxymortar.Harriman Interchange Ramp(1979)—This is a three-span, two-lanePCI JOURNAL/March-April 1986ramp carrying AADT 9000. Each span is75 ft (23 m) long. The roadway is on an800 ft (244 m) radius horizontal curve.The roadway is also on a vertical curveand is superelevated. Individual spansare markedly skewed. Fig. 22 shows aview of the bridge. The NYSTA let acontract on the complete rehabilitationof this bridge. The connection details ofthis structure are similar to those shownin Figs. 18 and 19.Based on available drawings of theexisting structure and an actual fieldsurvey, a computer program was written to generate numerical tables of eachprecast concrete slab panel and plotout their geometries for verification.This information was incorporated inthe contract drawings and the slabpanels were fabricated accordingly.Full width panels, 8 in. (203 mm)thick by 4 x 54 ft (1.2 x 16.5 m) coveredabout 9000 sq ft (840 m l ) of deck area.Traffic was maintained using a detourramp.59

Although NYSTA had similar constniction experience behind it, this wasthe first such project for the contractor.Perhaps for this reason, the epoxy mortar was found to be of unsatisfactoryquality at some places with evidence ofimproper proportioning. Structuralweakness of the spans is not suspectedbut cracking and some leakage throughthe panel joints has been detected.37The design and construction of thisbridge were admittedly very complex.The problems encountered emphasizethe need for careful inspection of materials and components in this type of construction.Fig. 23. Clark Summit Bridge, Pennsylvania Turnpike Commission.Fig. 24. Placement of new precast panel deck and deteriorated condition of old deck(Clark Summit Bridge).60

Pennsylvania TurnpikeCommissionClark Summit Bridge (1980)—This1627 ft (496 in) long bridge consists oftwo parallel structures carrying twolanes each way.35 -40 Its peak point isabout 140 ft (43 m) high.Fig. 23 shows a view of the bridge.Fig. 24 shows placement of panels atone of the structures while two-waytraffic was maintained using the parallelstructure. The figure also shows the severely deteriorated condition of thedeck at the time of rehabilitationTypically, 6% in. (171 mm) thick slabpanels were 7 ft (2.1 m) long with a fullroadway width of 29 ft (8.8 m) weighing18,000 Ibs (8165 kg) each.Elastomeric strips and epoxy mortargrout were used for bedding over existing stringers. Non-shrink cement groutwas placed at the transverse joints andnominal longitudinal post-tensioningwas used. Fig. 25 shows manual longitudinal tensioning. The deck structurewas noncomposite.Similar details were used in the redecking of another bridge which is de-scribed next.Quakertown Interchange Bridge(1981)—Fig. 26 shows the two-lane divided interchange overpass and Fig. 27(top) shows a schematic elevation of thestructure. This is a suspended cantileversystem with composite deck in the suspended span and noncomposite deck inthe cantilever span.Precast panels, 6'/a in. (165 mm) thickwith varying haunch thickness, are 7 ft71/4 in. (2.3 rn) long and 17 ft 6 in. (5.3 m)wide (see Fig. 27 (bottom) I and coverone-half the width of the structure. Acast-in-place concrete median barrierwas installed between two half-widthprecast panels. Figs. 27 (bottom) and 28show the slab panel sizes and connection detail, respectively.Existing bulb angle shear connectorswere left in place as the old slab wasremoved. The slab panels with shearpockets were cast with sufficient precision that the precast slab fitted wellwhen set in place. EIastomeric stripswere glued to the top of the flanges tocontain the epoxy mortar which provided uniform bedding of the precastpanels.Fig. 25. Longitudinal post-tensioning (Clark Summit Bridge).PCI JOURNALMarch-April 198661

FFig. 26. Quakertown Interchange Bridge, Pennsylvania Turnpike Commission.1nflComposite with Shear ConnectionsUF.T.99-OSCHEMATIC ELEVATIBridgeF.-17'-6"PLAN OF SLAB PANELSFig. 27. Schematic elevation and panel dimensions, Quakertown Interchange Bridge.62

Existing Bulb AngleLatex Concrete Grout — 7ConduitForLongifudino Post TensionLatex ConcreteOverlayI"x 1 3/8 1 ElostomeEpoxy MorterBeddingSHEAR CONNECTOR DETAILLatex Concret(1 X 1 3/8 ElastomerBridge Tie AnchorEpoxy Morter BedCover PlateHOLD DOWN DETAILFig. 28. Connection details, Quakertown Interchange Bridge.This method allowed the precastpanels to ride over the existing coverplates in the negative bending momentregion. Latex modified concrete wasused in both the shear pockets andtransverse panel joints. The transversejoints were pulled together by usingnominal longitudinal post-tensioning.Latex modified concrete was also usedas the riding surface overlay.In addition to providing rapid erection, the construction of the two bridgesdescribed above has proven to be costeffective compared to conventional deckreplacement methods. These twobridges have also performed extremelywell.PCI JOURNAL/March-April 1986Massachusetts TurnpikeAuthorityConnecticut River Bridge betweenWest Springfield and Chicopee —Fig. 29shows an overview of this 1224 ft (373 m)long, four-lane divided highway. A typical interior span is 224 ft (68 m) long.Figs. 30(a) and 30(b) show the elevationof a typical span together with the crosssection of the bridge.Separate twin east and west boundroadway decks are supported on cornmon floor beams. Traffic was maintained by restricting construction to oneside of the bridge which allowed twoway traffic on the other side. The reha63

Fig. 29. Connecticut River Bridge, Massachusetts Turnpike Authority.Typical Interior Span 224'-O (Max.)Total Bridge Length 1224 -0 Overall(a) TYPICAL INTERIOR SPANEastboundWestbound4-0"(b) TYPICAL CRASS SECTIONFig. 30. Schematic elevation and section of typical span, ConnecticutRiver Bridge.64

bilitation of the east bound roadway was pretensioned and longitudinally postcompleted and opened to traffic before tensioned. To reduce the dead load,the target date. The west hound road- lightweight aggregate concrete [115 lb/way was completed in 1982.ft (1842 kg/m') ] withf, 5000 psi (34.5The precast slabs were transversely MPa) was used for the precast concreteti -5-270 K Strandsfor Pre Tension(!2 Total)----1'5-frunverC U' ftt:98'-1 1/2'-I ½! 8III11atOblong Holes forShear StudsConduit for Post'Stringer (Typ)Tension (t9 Total)PLAN OF TYPICAL PRECASTPRESTRESSED LIGHTWEIGHT CONCRETE SLAB PANELThreadedSncket farLevelingWaterproof MembraneBituminousOverlay rNor—Shrink Grout\J.:0U,. w.UII/2 3/4C)0tiEn01uC)a-m6 x 6 —W4n W4 WeldedWire Fabric1/8I/2" Dia- ETHAFOAM Backer RodTRANSVERSE JOINT SECTIONFig. 31. Typical panel dimensions and transverse joint detail, Connecticut River Bridge.PCI JOURNAL/March -April 198665

ai4-Existing StringerVERTICAL ADJUSTING DETAILS'eadOVU,TYPICAL SLAB-STRINGER CONNECTIONFig. 32. Slab and stringer connection details, Connecticut River Bridge.200'------ 100 --- f--- 200,Fig. 33. Bridge No. 1 over Rondout Creek, New York State Department of Transportation(NYSDOT).66

!'ftIII204l" Conduitfor 2 " d Tie Rodtot ea. Stringer Line (TYP)PrestressedStrand l -IO.0P.F6aaa'r211 X6 1 'x8'3 11Elast. Padson Strinaers. IIH4x4 2 longStud boltStringerFloor BeamFig. 34. Connectio

Even in many newer structures deck deterioration is becoming increasingly evident. Local patching and overlaying can be used as short-term repair methods dur-ing the early phases of deterioration. Eventually, total replacement of the deck is required. This is illustrated in Fig. 2. Cast-in-place concrete deck is often used as a replacement deck .