2004 PCI DESIGN AWARD WINNER

Design and Construction ofthe Old 99 Bridge — An HPCSpliced-Girder Structure

Khashayar Nikzad, Ph.D., RE.Principal/PartnerTranTech Engineering, LLCBellevue, Wash.

Theo Trochalakis, Ph.D., S.E.Principal

TranTech Engineering, LLCBellevue, Wash.

Stephen J. Seguirant, RE.,FPCJVice President and Director ofEngineering

I Concrete Technology Corp.Tacoma, Wash.

Bijan Khaleghi, Ph.D., RE.Concrete Specialist

Bridge and Structures Office ,

Washington State Department ofTransportation L.—

Olympia, Wash.

This article describes the design and construction ofthe Old 99 (Riverside) Bridge, an 850-ft-long (260m), 72-ft-wide (22 rn), five-span, post-tensioned,

spliced-girder bridge spanning over the Skagit River

in Washington State. In 2004, this bridge won a PCIDesign Award. The bridge’s superstructure consists

of recently developed Washington State Department

of Transporation W95PTG “supergirder” sections.

These precast concrete girder sections were

transported to a staging area close to the site, where

they were spliced into single pieces that produced

maximum spans of 180 ft (55 m). After delivery tothe site, the post-tensioned girders were erected

on top of the piers with no intermediate temporarysupports. High-performance concrete (HPC), with

design strengths of 7.5 ksi (52 MPa) and 10 ksi (69

MPa), was specified for the cast-in-place splices

and precast supergirder segments, respectively. The

use of HPC allowed a high initial post-tensioning

force to be applied to the precast concrete girders.

Special attention was paid to the lateral stabilityduring erection and time-dependent camber of theassembled girders.

98 PCI JOURNAL

The Old 99 (Riverside) Bridgelinks the twin cities of MountVernon and Burlington in north

western Washington (Fig. 1). Thebridge’s superstructure consists of three180-ft-long (55 m) interior spans andtwo 150-ft-long (46 m) end spans. Thesespans are supported by the recently developed Washington State Departmentof Transporation (WSDOT) W95PTGprecast concrete “supergirder” sections,which serve as longitudinal stringers.The superstructure is semi-integral atthe abutments and hinged longitudinally at the interior piers. Figure 2 showsplan, elevation, and cross-sectionalviews of the Old 99 Bridge.

The Skagit Valley is located betweenthe Cascade Mountains (to the east) andthe Pacific Ocean (to the west). Strongatmospheric currents produce a prolonged rainy and windy winter seasonand massive accumulations of snow inthe mountains. The river is prone toflooding in the winter from rain andin the spring from melting snow in

the mountains. This flooding results inlarge quantities of debris drifting pastthe bridge site, including large logs.

Intennediate, temporary bridge supports, which are often slender, cannotbe expected to survive the impact fromthe debris if they remain in the riverchannel during the flooding seasons.Moreover, for the protection of migrating salmon, the permissible windowfor construction in the river is limitedto only four months per year, from thebeginning of July through the end ofOctober. The regulating environmentalagencies do not permit falsework to remain in the river channel outside of thisconstruction window.

Considering these physical and environmental constraints, the use of temporary, intennediate construction false-work supports between the permanentbridge piers was ruled out, and a designconcept based on erection of a single-piece girder was implemented. Usingprecast concrete hammerheads anddrop-in middle segments also require no

intermediate falsework; a cost comparison, however, revealed that this alternative would have been more expensive.

BACKGROUND

Although bridges constructed withprecast, prestressed concrete girders have a proven economic value,require little or no maintenance, andare aesthetically pleasing, the use ofsuch girders is rare in cases where themaximum span lengths stretch beyond160 ft (50 rn).1

There are many reasons for thisanomaly, including material-performance limitations, weight limitationson girder handling and shipping, and alack of general guidelines for the designand manufacture of longer, precast concrete girders. Through the developmentof high-performance concrete (HPC),2more efficient girder shapes,3 and otherenhancements, the range of spans forwhich precast, prestressed concretegirders are used has steadily increased.

Fig. 1. Aerial view of completed Old 99 Highway Bridge over Skagit River, Washington, looking south.

January—February 2006 99

Fig. 2. Plan and elevation of Old 99 (Riverside) Bridge.

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One of the major limitations associated with achieving longer spans hasbeen the maximum hauling weightof the precast concrete girders.Presently, Washington has a 200 kip(890 kN) weight limit for these girders.4 For a WSDOT W95G section,

which is the pretensioned version ofthe girder section bsed on this project,this hauling weight limit correspondsto a prestressed concrete girder approximately 167 ft (50 m) long.

Because of this weight limitation,the concept of splicing a precast con-

crete girder has gained more attentionrecently.5’6This entails fabricating individual girder segments and transporting the segments to the site, where thesegments are then spliced into a singleunit by a site assemblage procedure,such as post tensioning.

Some of the advantages of the splicedgirder concept are longer spans, fewersubstructure units, increased girderspacing, rapid construction, enhancedaesthetics, and reduced superstructuredepths. The Old 99 Bridge uses bothHPC and spliced-girder technologiesto achieve a maximum span of 180 ft(55 m), in a one-piece erection processthat requires no intermediate construction falsework.

DESIGN CONSIDERATIONS

The 850 ft (260 m) length was dictated by the river hydraulics and theexistence of a flood-control dyke ateach riverbank. To promote competition among local contractors, two design options were prepared: one withprecast, prestressed concrete girderswith five continuous spans (150 ft [46 m]end spans and 180 ft [55 m] interiorspans) and one with steel plate girders with three continuous spans of 270ft, 300 ft, and 270 ft (82 m, 90 m, and82 m).The contractor with the lowestbid, Kiewit Pacific Co., chose the concrete alternative. Its bid was 12% lowerthan the steel alternative.

Spliced Girder Concrete Alternative

The design goal for the concretealternative was to minimize the number of girders per span and the number of piers in the river. The WSDOTW95PTG girder sections were developed by the Pacific Northwest Precast!Prestressed Concrete Institute in collaboration with the WSDOT, with theintention of increasing the span capabilities of precast, prestressed concretegirders.

Transportation constraints and weightlimitations prevented the precastingand pretensioning of the girders in asingle piece, so the girders had to beproduced and transported in segments.Furthermore, due to environmentalconstraints, the precast concrete girdersegments needed to be assembled bypost tensioning them at a staging yard

Fig. 4. Stage 1 post-tensioning determination flowchart.

102 PCI JOURNAL

near the site. After being transportedfor about 2 miles (3 km), they would beerected on top of the piers, one wholepiece at a time, without using any intermediate falsework.

The WSDOT W95PTG “supergirder” sections were selected for the bridgesuperstructure. Concrete TechnologyCorp. in Tacoma, Wash., fabricatedthe girder segments, which were transported to the staging yard and splicedtogether with Stage 1 post tensioning.

After the concrete at the closurepours (between adjacent precast segments) achieved its design strength,the spliced girders were transported toa work bridge adjacent to the structureand erected as simple spans. Followingerection, and placement and hardeningof the deck and the diaphragms overthe piers, the spliced girders were integrated into a continuous compositebridge using Stage 2 post tensioningover the bridge’s entire length.

The bridge substructure consists of7-ft-diameter columns (2.1 m) resting ontop of 9 ft 10 in. diameter shafts (3.0 m)that extend an average of 90 ft (27 m)below the river’s mudline. Deep alluvial deposits of soft soil in the riverbedand a seismically sensitive site withliquefaction potential dictated the useof deep foundation drilled shafts. Thesubstructure connections to the superstructure consist of longitudinal hingesconnecting the cap beams to the pierdiaphragms (Fig. 2). Figure 3 shows aschematic of the construction sequence.

Design Details

An important design parameter of thespliced girder is the concrete strengthrequired at the splice locations; the site-cast concrete strength is usually not ashigh as the plant-cast girder segments.

In the early stages of design, the28-day design strengths for the closurepours and precast concrete segmentswere set at 6.0 ksi (40 MPa) and 8.5 ksi(60 MPa), respectively. A closure pouris the short segment of concrete cast atthe staging yard between adjacent precast concrete segments at a splice location. Because of these strength limitations, the simple-span post tensioning(Stage 1) had to be broken into twosubstages, namely, “assembly” phaseand “after-erection-and-prior-to-slab-pour” phase.

This was due to the stresses inducedby handling and hauling the splicedgirders at the site. Through the useof HPC, the 28-day design strengthfor the precast concrete segmentswas increased to 10 ksi (70 MPa),and the strength for the closure poursconcrete was increased to 7.5 ksi (50MPa). These higher strengths allowedthe designers to combine the twopost-tensioning substages into one.

For transportation and handlingpurposes, the precast concrete super-girder segments were pretensionedwith twelve 0.6-in.-diameter (15 mm),270 ksi (1860 MPa) prestressingstrands. Stage 1 post-tensioning requirements were based on satisfyingvarious criteria, such as allowable service level stresses, ultimate strength,lateral stability, and camber.

The flowchart in Fig. 4 illustrates theiterative design procedure for determining the Stage 1 post-tensioning requirements. Two of the very important,but less investigated, blocks in thisflowchart are the lateral stability andthe time-dependent deflection characteristics of the spliced girders.

Lateral Stability

The top flange of precast concretegirders have the tendency to bend laterally during lifting and transporta

tion because of construction tolerancesin girder manufacture on the locationof prestress and lifting loops, and theoften soft, torsional stiffness of trucksand dollies. Researchers have investigated lateral stability during lifting andtransportation of precast, prestressedconcrete girders.7-9To investigate theinfluence of the parameters involved,a numerical study1° was performed.Figures 5, 6, and 7 show the results obtained from this study.

The results indicate that all the safetyfactors associated with the lateral stability of the assembled girders duringtransportation are satisfied if the sumof the transportation dolly rotationalspring stiffnesses exceeds 55,000 k-inirad(6200 kN-mlrad). The required 28-dayconcrete strength associated with thisrotational stiffness at the closure pourlocations is calculated to be 7.2 ksi (50MPa). Moreover, to enhance the lateralstability of the assembled girders, eight0.6-in.-diameter (15 mm), unbondedtemporary strands were placed in thetop flange.

Camber and Deflection

The original design for acceptabledeflections called for the elimination orminimization of the negative camber.For this purpose, the time-dependentdeflections of the girders were evalu

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January—February 2006 103

ated using CONSPLICE® software,which is marketed by Leap Corp.”

A comparative study was performedto investigate the deflection characteristics of these long, spliced supergirders. In the study, the deflection characteristics of a simple beam made upof a standard WSDOT W74G girderwith a span of 125 ft (38 m) was corn-

pared with a simple beam made up ofa W95PTG spliced girder with a spanof 180 ft (55 m). Both beams were designed for a typical HS-25 loading.

For the climatic conditions, cement,aggregates, and prestressing and curingpractices used in Washington, WSDOTfound that the major and significant partof camber is relieved while the gird-

ers are simply supported.12 This condition prevails up to the hardening ofthe deck. Once the deck has hardened,the resulting composite girder sectionsbecome very stiff, and the additionalcamber required to compensate for allloads applied to the composite girdersis comparatively small and practicallyinsignificant.

For this reason, the camber diagramsof the W74G and W95PTG girdersshown in Fig. 8 and 9 are for the initial period while the girders are simplysupported. Unlike the W74G girder,whose design is governed by servicestresses at a few critical locations, thedesign of a spliced W95PTG girder(that is, the required Stage 1 post tensioning) is governed by camber.

In this example, the Stage 1 posttensioning of the W95PTG girder consisted of three tendons of twenty-two0.6-in.-diameter (15 mm) strands. Asshown, the W95PTG section exhibitsa small negative camber by the timethe deck concrete has hardened or thesuperstructure has been transformedto a composite section, even under ahigh post-tensioning force, unlike theW74G section.

The Stage 2 continuity post tensioning consisted of two tendons. Onelarge tendon consisted of twenty-two0.6-in.-diameter (15 mm) strands, andone small tendon consisted of four0.6-in.-diameter (15 mm) strands. Theoretical deflection calculations indicatethat the Stage 2 post tensioning wouldcause an instantaneous upward deflection of approximately 0.5 in. (13 mm)on the composite section. Due to thelarge number of precast concrete segments that needed to be spliced, unintended tendon deviation angles at theclosure pours were expected.

The main purpose of the small continuity tendon was to serve as a reservecapacity source and would be stressedonly if the frictional losses exceededthe theoretical calculation. Moreover,to address the threading issue of the850 ft (260 m) tendons, the ratio ofduct area to the area of strands in atendon was specified as a minimum ofthree. Figure 10 presents Stage 1 andStage 2 post-tensioning details, whileFig. 11 shows the reinforcement details including all the prestressing usedat different phases of construction.

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Fig. 7. Lateral stability factor of safety versus dollies’ stiffnesses.

104 PCI JOURNAL

CONSTRUCTION

Construction of the bridge’s substructure and erection of the girderstook two in-water construction windows to be completed. If temporarysupports had been required for casting of the intermediate splices, anotherconstruction window would have beennecessary, extending bridge completion for another year.

The contractor was responsible forworker safety during construction. Indeed, the scheme for the transportationof the girders and their subsequent erection was technically sound and appropriate for the long girders and the roadconditions at the construction site.

Accidental torsional buckling ofthe girders was avoided by providinga pinned front dolly and a torsionallystiff, back double dolly. The use of arear tandem dolly system, with a rotational stiffness of approximately260,000 k-in./rad (29,000 kN-mlrad),far exceeded the design requirement.Figure 12 shows the transportationconfiguration.

It should be noted that the equipmentused to transport the spliced girders isintended for moving heavy loads overa short distance; it is not appropriatefor use on the open road and wouldnot meet the permitting requirementsfor such a haul. The ability to use suchequipment was one advantage of assembling the girders at a staging yardnear the site.

The lateral stability of the girders was sensitive to the distance fromthe end of the girder to the pick point(distance a).7’8 A relatively small increase in a increases the girder’s lateralstability considerably. In the contractdrawings, the distance a was specifiedas 15 ft (4.6 m). The contractor proposed reducing this distance to only7 ft (2.1 m) to accommodate the capacities of the cranes and the work bridge.

Despite a marginal safety factor,which was slightly higher than thedesign (or code-required) minimum,all girders were lifted and placedon top of the piers satisfactorily.Figure 13 shows the erection of these177.5 ft (54 m), 122 ton (1085 lcN),spliced W95PTG girders.

Because of the large diameter ductswithin the girder webs, there was mad-

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January—February 2006 105

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equate space on either side of the ductand on the faces of the girder webs toembed high-strength tensile bars orstrands to serve as pick-up hoops. Consequently, an external lifting assemblywas developed.

This assembly included four high-strength tensile bars, two on either sideof the girder web, which were posttensioned at the site prior to transportation and subsequent lifting. The external lifting concept was included in thebridge’s contract drawings. The contractor designed, supplied, and used thelifting devices successfully.

The contractor used a temporarywork bridge throughout the construction of the bridge’s substructure andduring girder erection. It was installedin the river channel, and was later removed at the beginning and end ofeach of the 2001 and 2002 constructionwindows. The work bridge compriseda timber deck, steel girders, and steelpipe piles.

Drilled shafts were installed by aLeffer oscillator operating from thework bridge’s finger extensions. Twodifficulties were encountered initially.Due to the large frictional forces thatwere generated between the interiorface of the drilling casing and the partially hardened concrete, large extracting forces were created during the removal of the casing. These forces wereinitially counteracted by four reactionpiles per shaft platform, but as the bearing capacity of the bearing piles wasexceeded by the platform supportingthe oscillator operation, the whole platform tilted. This problem was resolvedby increasing the penetration depth ofthe platform’s reaction piles and by increasing the number of piles from fourto eight per platform.

The other difficulty consisted ofsome casing extraction problems dueto the hardening of the concrete. Concreting the shaft in predetermined increments of 20 ft (6 m) and extractingthe shaft’s casing segments during thereverse-ocsillation activity resolvedthis difficulty.

This procedure continued until concrete was placed in the entire shaftand the shaft casing was completelyextracted. Keeping the time it took tounbolt and remove a given casing segment to under an hour was the key to a

successful operation, as well as usingconcrete with retarding admixtures todelay hardening.

Due to the complex nature of thespliced-girder deflections and the variability of the material properties amongthe girder segments, prediction of defiections—even with a nonlinear time-dependent analysis—was expected tobe imprecise. To prevent the possibil

ity of having a sagging bridge, an adjustment was introduced to the contractdrawings during the design phase. Thisadjustment was made possible by introducing a variable haunch height ontop of a given girder.

The variable haunch height was defined as the x distance in the contractdrawings. Prior to placing the deck, elevations of the top of the girders were

Fig. 12. Spliced girder hauling activities with pinned front dolly and torsionally stiffback double dolly.

Fig. 13. Spliced girder erection activities showing external lifting assembly.

January—February 2006 107

Fig. 14. Girder splicing activities.

determined and the values of the x distances were calculated for each girder.Hence, the desired grade of the bridgewas obtained both longitudinally andtransversely. Figures 14 and 15 showthe construction of the bridge at various stages of creation.

CONCWSION

In this article, the authors have discussed special design and constructionchallenges, and their associated engineering solutions, in the constructionof the Old 99 (Riverside) Bridge. Itssuccessful completion demonstratesthat spliced-girder technology can be

applied to girder lengths that are beyond the customary spans and transverse spacing of standard precast,prestressed concrete girders. This particular method of bridge constructionrequires no precast pier segments ortemporary, intermediate supports.

As a future enhancement, and to fullymobilize the potential of this concept, itis recommended that the American Association of Highway TransportationOfficials load-resistant factor designmethod of calculating live load and impact moments be used, especially wherethe entire deck is analyzed as a grid, including any transverse post tensioningof the intermediate diaphragms.

In 2004, the Old 99 Bridge won a

PCI Design Award for “Best Bridgewith Spans Greater than 135 ft.” Thejury comments were as follows:

“We think this type of bridge will beused more and more often in the future.It uses girder segments spliced togetherat the job site to eliminate transportation and site constraints. Assemblingthe girders near the site and erectingthem in one piece eliminates falseworkproblems. This technique enabled180-ft spans; it also helps get piersout of the way, which in this particular Northwestern environment, were aproblem in collecting debris. If thesegirders were cast in one place, theywould have weighed 122 tons, whichwould have precluded shipping themto the site. So, splicing them at thesite made the project feasible by alsoeliminating the need for falsework inthe river.”

ACKNOWLEDGMENTS

Two of the authors of this paper areformer employees of MACTEC Engineering and Consulting, Inc. Theythank the organization for providingthem with the opportunity to be involved in this exciting project.

Many individuals were instrumentalin the success of this project. To namea few, the authors thank: John Buckley,Director of Public Works; Dan Eisses,Project Manager; and Mike Love, Capital Improvement Manager at the Cityof Mount Vernon, Wash.; Mark Hammer, Project Engineer—WSDOT NWregional office; and Vigil Schmidt,WSDOT Assistant Construction BridgeEngineer.

The authors thank Bob Elliott, Project Sponsor Kiewit Pacific Co., for hisassistance.

In addition, the authors express theirgratitude to Bob Mast of BERGERJABAM, Federal Way, Wash., for hisinput on the lateral stability of thegirders during transportation; KunleOgunrinde; Ray Steege, MACTECTransportation Business Line Leader;and David Lanning for his valuablecontributions during the course of thisproject.

Finally, the authors thank the PCIJournal reviewers for their constructive suggestions.

108 PCI JOURNAL

CREDITS

Owner: Cities of Mount Vernon andBurlington, Wash.

Designer: MACTEC Engineeringand Consulting, Inc.; Bellevue, Wash.

Precaster: Concrete TechnologyCorp.; Tacoma, Wash.

General Contractor: Kiewit PacificCo.; Vancouver, Wash.

Post-Tensioning Subcontractor: AvarConstruction Systems, Inc.; Campbell,Calif.

REFERENCESCastrodale, R. W. and White, C. D.,“Extending Span Ranges of PrecastPrestressed Concrete Girders,” NCHRPReport 517, Washington, DC, 2004.

2. Weigel, J. A., Seguirant, S. J., Brice, R.,and Khaleghi, B., “High PerformancePrecast, Pretensioned Concrete Girder

Bridges in Washington State,” PCIJournal, V. 48, No. 2, March—April2003, pp. 28—52.

3. Seguirant, S. J., “New Deep WSDOTStandard Sections Extend Spans ofPrestressed Concrete Girders,” PCIJournal, V. 43, No. 4, July—August1998, PP. 92—119.

4. Van Lund, J. A., Kinderman, P. D., andSeguirant, S. J., “New Deep WSDOTGirders Used for the Twisp RiverBridge,” PCI Journal, V. 47. No. 2,March—April 2002, pp. 20—31.

5. Abdel Karim, A. M. and Tadros, M. K.,“Design and Construction of Spliced I-Girder Bridges,” PCI Journal, V. 37,No. 4, July—August 1992, pp. 114—122.

6. Nicholls, J. J. and Prussack, C.,“Innovative Design and ErectionMethods Solve Construction of RockCut Bridge,” PCI Journal, V. 42, No.4, July—August 1997, pp. 42—55.

7. Mast, R. F., “Lateral Stability ofLong Prestressed Concrete Beams,

Part 1,” PCI Journal, V. 34, No. 1,January—February 1989, Pp. 34—53.

8. Mast, R. F., “Lateral Stability ofLong Prestressed Concrete Beams,Part 2,” PCI Journal, V. 38, No. 1,January—February 1993, pp. 70—88.

9. limper, R. R. and Laszlo, G., “Handlingand Shipping of Long Span BridgeBeams,” PCI Journal, V. 32, No. 6,November—December 1987, pp. 86—101.

10. Nikzad, K., Trochalalcis, T., andOgunrinde, K.. “Challenges Encountered in Design and Construction of aMulti-Span Post-Tensioned Spliced-Girder Concrete Bridge,” Proceedings,First Annual Concrete BridgeConference, Nashville, TN, October2002.

11. Tooralc, Z., Consplice PT, LeapSoftware Inc., Tampa Bay, FL, 2002.

12. Bridge Design Manual, WashingtonState Department of Transportation,Program Development Division,Olympia, WA.

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