Design-Construction of Bridge Street Bridge – First CFRP

The design, fabrication, and erection – and theresearch leading up to this cutting-edgetechnological achievement in civil engineering –are presented, as well as the long-term monitoringprogram and ongoing research that will continue.The Bridge Street Bridge in Southfield, Michigan, isthe first vehicular concrete bridge ever built in theUnited States that uses carbon fiber reinforcedpolymer (CFRP) material as the principal structuralreinforcement. The project consists of two parallelbridges – Structures A and B – over the Rouge Riverin the City of Southfield. Both structures use threeskewed spans, each over 62 m (204 ft) long, tocarry vehicular traffic. Structure A consists of a newsubstructure as well as a new superstructure, andincorporates five equally spaced conventionalAASHTO Type III girders in each of its three spans.Its cast-in-place concrete deck slab is placedcontinuously across the three spans. Structure Bconsists of 12 special double-tee (DT) girders (fourper span) using pretensioned LeadlineTM tendonsand post-tensioned carbon fiber composite cable(CFCC)TM strands. This project recently won PCI’sHarry H. Edwards Industry Advancement Award.

The Bridge Street Bridge consists of two separate par-allel and independent bridges (Structures A and B)over the Rouge River in the City of Southfield,

Michigan (see Figs. 1, 2, and 3). Both bridges comprisethree spans skewed at 15 degrees over a 62 m (204 ft)length and carry traffic for an industrial subdivision. Struc-ture A was constructed first, and it consists of a new sub-structure and a new superstructure that incorporates fiveequally spaced conventional AASHTO Type III precastconcrete I-girders in each of the three spans, with a continu-ous cast-in-place concrete deck slab.

Design-Construction of BridgeStreet Bridge – First CFRP Bridgein the United States

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Nabil F. Grace, Ph.D., P.E.Professor and ChairmanCivil Engineering DepartmentLawrence Technological UniversitySouthfield, Michigan

Frederick C. Navarre, P.E.Chief Structural Engineer

Hubbell, Roth & Clark, Inc.Bloomfield Hills, Michigan

Richard B. Nacey, P.E.Senior Project EngineerHubbell, Roth & Clark, Inc.Bloomfield Hills, Michigan

Wayne Bonus, P.E.Administrative Engineer

City of Southfield, Michigan

Loris Collavino, P.Eng.PresidentHollowcore Incorporated/Prestressed Systems, Inc.Detroit, Michigan

HARRY H. EDWARDS AWARD WINNER

September-October 2002 21

Structure B consists of four specialprecast, prestressed double-tee (DT)girders in each of the three spans con-figured as simply supported spans.Each DT girder is structurally rein-forced using pretensioned carbon fiberreinforced polymer (CFRP) LeadlineTM

tendons* and post-tensioned CFRPcarbon fiber composite cable(CFCC)TM strands† in both longitudinaland transverse directions. The non-pre-stressed reinforcement in the girdersand deck structure consists of CFCCstrands manufactured in bent configu-rations, straight CFCC reinforcingbars, CFRP NEFMACTM grid rein-forcement,‡ and stainless steel reinforc-ing bars for stirrups.

Ultimately, this project is expectedto demonstrate that the use of CFRPmaterial as structural reinforcementcan increase the service life of high-way bridges, thereby reducing con-struction-related safety concerns andannual maintenance costs. To optimizebridge durability even further, a qual-ity review of materials was conductedand decisions were made to require

* Leadline tendons manufactured by Mitsubishi Chemical Corporation, Japan.

† CFCC strands manufactured by Tokyo Rope Mfg.Co., Ltd., Japan.

‡ NEFMAC grid reinforcement manufactured by Autocon Composites, Inc., Ontario, Canada.

Fig. 1. (top photo) Bridge Street Bridge, Southfield, Michigan, looking south, withCFRP Structure B on the right. (bottom photo) Side view of Structure B.

Fig. 2. Cross section of Bridge Street Bridge: Structure A has conventional AASHTO Type III girders and a new substructure.Structure B is the CFRP double tee bridge supported by an existing substructure.

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very high quality concrete and toallow metallic reinforcement madeonly of stainless steel.

Hollowcore Incorporated (HI),Windsor, Ontario, Canada, fabricatedall the girders for both structures,

while Construction Technology Labo-ratories, Inc. (CTL), Skokie, Illinois,installed the instrumentation for long-term monitoring.

The current state of the art in re-search1 underscores an increasing in-

Table 1. Properties of Leadline tendons and CFCC strands.

Property Leadline CFCC 1 × 7 CFCC 1 × 37Nominal diameter,

0.39 (10) 0.5 (12.5) 1.57 (40)in. (mm)

Effective cross-sectional area, 0.111 (71.6) 0.118 (76.0) 1.17 (752.6)

sq in. (mm2)Guaranteed tensile strength,

328 (2.26) 271 (1.87) 205 (1.41)ksi (kN/mm2)

Specified tensile strength, 415 (2.86) 305 (2.10) 271 (1.87)

ksi (kN/mm2)Modulus of elasticity,

21,320 (147) 19,865 (137) 18,419 (127)ksi (kN/mm2)

Elongation, percent 1.9 1.5 1.5Guaranteed breaking load,

36.4 (162) 31.9 (142) 240.5 (1070)kips (kN)

Ultimate breaking load, 46 (204.7) 36 (160) 316.9 (1410)

kips (kN)

Table 2. Properties of NEFMAC grid and precast concrete.

Property NEFMAC grid Precast concreteModulus of elasticity, ksi (GPa) 12,540 (86.5) 4,960 (34.2)

Ultimate strength, ksi (MPa) 217 (1500) 7.12 (49.1)*Ultimate strain, percent 1.8 0.25

* Refers to average 28-day strength of concrete.

terest in advancing the technology ofcivil engineering infrastructure pro-jects, including bridge girders andslabs that use advanced carbon fiberreinforced polymer (CFRP) materials.Despite the large-scale worldwide re-search to find the suitable fiber rein-forced polymeric (FRP) materials, thenumber of prestressed concretebridges in North America using CFRPmaterials for prestressing is stillsmall.1-4

Extensive research5-16 conducted atthe Structural Testing Center atLawrence Technological University(LTU) in Southfield, Michigan, andthe University of Windsor in Ontario,Canada, has resulted in a large amountof data on the response of various con-figurations of one-third scale straightand skewed bridge models. The find-ings of these investigations, funded bythe National Science Foundation,served as the basis on which this pro-ject was designed and constructed.

The purpose of this paper is to de-scribe the new type of construction, aCFRP reinforced and prestressed con-crete bridge, as demonstrated by theBridge Street Bridge (Structure B),during various phases of its construc-

Fig. 3. Plan view of the bridge, with instrumented CFRP double tee girders and conventional AASHTO I-girders identified(dimensions in SI units).

ABUTMENT

BACK WALL

ABUTMENT

BACK WALL


tion. In addition, the values of variousparameters such as pretensioningforces in Leadline tendons, concretestrains, early-age deflections, andpost-tensioning forces in external un-bonded CFCC strands (longitudinaland transverse), measured during thevarious construction stages, are pre-sented and discussed.

FULL-SCALE DT GIRDER TEST

Because of the lack of design guide-lines for CFRP prestressed concretebridges in the United States and else-where, several design assumptions5,10

had to be made during the design stageand throughout the preparation of theconstruction documents. To ensure the

Fig. 4. Cross-sectional details of Structure B (dimensions in SI units).

Fig. 5. Plan and elevation of Structure B, with transverse diaphragms identified.

success of the project, a multitask pro-gram was assembled for modeling,testing, monitoring, and acquiring rein-forcement and special services.

As part of this program, a full-scaleDT girder (the same design as that ofthe 12 DT girders used on this project)was constructed, instrumented, andtested to failure. This girder was fabri-

24 PCI JOURNAL

cated by HI and shipped to the CTLtesting facility in Skokie, Illinois. Thefindings there provided the informa-tion needed to confirm the design as-sumptions and aided the design teamin refining the fabrication details ofthe DT girders to be used for the pro-ject. The results of this testing pro-gram are not presented in this paperbut can be found elsewhere.15-16

BRIDGE DESIGNThe CFRP bridge, Structure B,

comprises spans with lengths of, from

south to north ends, 21.314, 20.349,and 21.429 m (69.9, 66.8, and 70.3 ft).The structural design is based onMichigan MS-23 truck loading (ap-proximately 1.25 times HS-20). The28-day design strength is 52 MPa(7500 psi) for the precast concretegirders and 38 MPa (5500 psi) for thecomposite concrete topping. Thecross-sectional details of Structure Bare shown in Fig. 4.

The bridge cross section consists offour precast DT sections and a mini-mum 75 mm (3 in.) thick non-continu-ous deck slab. As shown in Fig. 4, the

Fig. 7. Tensioningsystem arrangement

for the CFRPLeadline tendons.

10 MM CFRPLEADLINE

TENDONS

20 MM ∅ HOLE WITH PROTECTIVE

PVC TUBING

TRANSITION COUPLER

Fig. 6. Placement of non-prestressed CFRP reinforcement cage in single pan form.

precast section is 1220 mm (48 in.)deep, with a flange thickness of 150mm (6 in.). The total width of eachflange is 2120 mm (83.5 in.). Thebonded prestressed reinforcement inthe DT girders consists of ten rows ofthree 10 mm (0.39 in.) diameter CFRPLeadline tendons in each web. Thevertical distance between two adjacenttendon rows is 70 mm (2.8 in.). Non-prestressed longitudinal reinforcementincludes six rows of 12.5 mm (0.5 in.)carbon fiber composite cable (CFCC)strands in each web (two strands inRows 1 to 5 and four strands in bot-tom Row 6), and nineteen 10 mm(0.39 in.) diameter Leadline rods inthe flange. In addition, the flange is re-inforced with top and bottom layers oflongitudinal and transverse 10 mm(0.39 in.) diameter Leadline rods.

The composite topping is reinforcedwith NEFMAC grids The compositesection is also reinforced with four ex-ternally draped 40 mm (1.57 in.) di-ameter unbonded CFCC post-tension-ing strands. The tendons are drapedlongitudinally between DiaphragmsD2 and D6 (see Fig. 5) and bearagainst the bottoms of DiaphragmsD3, D4, and D5. At midspan (Di-aphragm D4), the depth of these ten-dons from the top surface of the com-posite concrete is 1118 mm (44 in.).

Transverse unbonded CFCC post-tensioning strands were installed

LOCK OFF

COUPLER


through each of the seven diaphragmsin each span; these strands were 21.8mm (0.86 in.) in diameter at end Di-aphragms D1 and D7, and 40 mm(1.57 in.) in diameter at interior Di-aphragms D2 through D6. These ca-bles were inserted along the 15-degreeskew through the four DT girders ofeach span.

For both transverse and longitudinalpost-tensioning, the unbonded strandswere stressed in stages to account fordifferent loading conditions. At theprecast plant, for example, longitudi-nal post-tensioning was partially ap-plied to help prevent cracking duringhandling, shipping, and erection.

The properties of the CFRP Lead-line tendons and CFCC strands aregiven in Table 1, while those of theNEFMAC grids and the precast con-crete are presented in Table 2. Thefabrication and instrumentation detailsof the bridge are presented in the fol-lowing sections.

FABRICATION OF DOUBLE TEES

A single pan form was used to fabri-cate the 12 DT girders. Fig. 6 showsthe placement of a non-prestressedCFRP reinforcement cage beingplaced into the single pan form at theprecast plant. The pan form accommo-dated the two stems, top flange, andseven transverse integral diaphragms.The compressive cylinder strengths ofconcrete for the 12 girders variedslightly with an average 28-day cylin-der strength of 55.8 MPa (8100 psi).The sequence of the fabrication proce-dure of the 12 girders is given below:

1. Installing the non-prestressedCFRP reinforcement, epoxy-coatedstainless steel stirrups, prestressingLeadline tendons, and other embeddeditems (see Fig. 6).

2. Pretensioning the Leadline ten-dons from the live end (see Fig. 7) andmonitoring the pretensioning forces atthe dead end (see Fig. 8).

3. Installing the vibrating wire straingauges on the Leadline tendons (seeFig. 9).

4. Placing and curing the concrete.5. Releasing the Leadline tendons

after the concrete achieved the desiredstrength.

(a) Dead end section with row numbers of tendons

(b) Pretensioning force measurements at dead end

Fig. 8. Monitoring of pretensioning forces of Leadline tendons at dead end.

Fig. 9. Vibrating wire strain gauge on Leadline tendons.

26 PCI JOURNAL

6. Removing the prestressed girderfrom the form.

7. Installing the longitudinal CFCCpost-tensioning strands and applying60 percent of the total post-tensioningforce just before shipping (see Fig.10).

Before stressing each Leadline pre-tensioning tendon, an aluminumsleeve was pressed on to both endswith a tapered steel wedge installedaround it. A threaded coupling sleevewas crimped on the ends and insertedinto steel guide sleeves that supportedthe tendons at the proper elevation andrestrained their rotation.

The ends of each tendon were in-serted into threaded anchor heads,which had a matching tapered interiorsurface. The dead end anchor headwas then positioned into the curvedsupport brackets and connected to thestressing bulkhead. The live end an-chor head was positioned within aslotted plate assembly that accommo-dated the elongation of the Leadlinetendons and also restrained tendon ro-tation (see Fig. 7).

Once supported, a short length ofconventional seven-wire steel pre-stressing strand was threaded throughthe anchorage bulkhead and insertedinto the transition coupler. The freeend of the steel strand was anchored atthe outside surface of the bulkheadusing a standard strand chuck.

The 60 straight Leadline tendons

Fig. 11. Erection of DT girders at the bridge site.

Fig. 12. Installed DT girders with external CFCC post-tensioning strands in place.

Fig. 10. Post-tensioning at the live end (left) and load cells installed at the dead end (right) for the longitudinal CFCC strands.


were stressed individually. The stress-ing sequence began with Row 10 (seeFig. 8a) and continued in the order ofRows 9, 1, 2, 5, 6, 3, 8, 4, and 7. Priorto pretensioning, load cells were in-stalled at the dead end of the selectedtendons to monitor the applied pre-stress force. Fig. 8b shows the ar-rangement of the load cells at the deadend.

The prestressing force in each Lead-line tendon was about 91 kN (20.5kips) after seating losses. After the

concrete achieved adequate strength,the Leadline tendons were released ina specific sequence. The time of ten-don release from girder to girder var-ied from 3 to 5 days. On average, theconcrete strength at the time of releasewas 44.1 MPa (6400 psi).

The four externally draped post-ten-sioning CFCC strands were installedin each DT girder at the precaster’syard prior to shipping. Fig. 10 showsthe installed CFCC strands (view frombelow the bridge). The draping of

these strands was achieved using aspecially designed tendon slide plateand a tendon alignment shoe placedbeneath Diaphragms D3, D4, and D5.Both the tendon slide plate and tendonalignment shoe are made of stainlesssteel.

The 13 mm (0.5 in.) thick steel ten-don slide plate was embedded in thecorresponding diaphragm using 12 x150 mm (0.5 x 6 in.) headed studs anda guide pin. The strand slide plate andstrand alignment shoe were connected

Fig. 13. Structure Bcompleted andready for traffic.

Fig. 14. Sectionthrough instrumentedDT girder at north endquarter span (lookingnorth).

CONCRETE DECKSLAB

10 MM DIAMETERLEADLINE CFRPTENDONS (TYP.)ELEVATION OF

TOTALPRETENSIONEDTENDON FORCE

CENTROID

46 MM OR JUST BELOWTOP OF TRANSVERSE

REINFORCEMENT

28 PCI JOURNAL

to each other using the same guide pinconnected to the diaphragm throughthe slide plate. The CFCC strandswere raised from below and posi-tioned within the strand alignmentshoe. A neoprene elastomeric protec-tive pad was placed between the align-ment shoe and the supported length ofthe strand to prevent surface damageto the strand.

As part of the monitoring program,load cells were permanently installedto measure and monitor the force lev-els in the CFCC strands of six DTgirders (the shaded girders identifiedin Fig. 3). In addition, strain gaugesand displacement transducers wereused to monitor the Leadline tendons

and the longitudinal CFCC strands inthe remaining six DT girders (un-shaded girders in Fig. 3).

Prior to post-tensioning each girder,all four 40 mm (1.58 in.) diameterCFCC strands were configured withload cells at one end. The load cellswere installed between the anchoragenut on the tendon sleeve and the bear-ing plate embedded in Diaphragm D6(see Fig. 10).

Post-tensioning was applied to thefour longitudinal CFCC strands in twodistinct stages. The initial post-ten-sioning consisted of applying approxi-mately 60 percent of the total post-ten-sioning force value [274 of 457 kN(61.6 of 102.7 kips)]; this took place

just before the girders were to beshipped to the bridge site. The final 40percent of post-tensioning wasachieved at the bridge site after thecomposite deck slab was placed.

BRIDGE CONSTRUCTIONThe unique construction method

was based on a process developed andtested previously at LTU.5-8 The trans-portation of the 12 girders from theprecast plant in Windsor, Ontario, tothe bridge site in Southfield, Michi-gan, required a special barging ar-rangement. The girders were erectedusing two large capacity cranes at op-posite ends of the bridge.

The four DT girders of the middlespan were erected first using bothcranes. The double tees of the north-and south-end spans, however, werehandled independently by the cranestationed closer to that particular span.

Fig. 11 shows the erection of a DTgirder for the south span, and Fig. 12shows the installed girders with exter-nal post-tensioning strands in place. Itshould be noted that all the transversepost-tensioning strands were pulledthrough their sleeves immediatelyafter erecting the girders and just priorto grouting the girder joints. Provi-sions were made to prevent grout fromleaking into the sleeves.

Construction of the bridge deck con-tinued with the application of first-stage transverse post-tensioning to theCFCC strands. The load cells were in-stalled between the anchorage nut onthe strand sleeve and the bearing plateembedded in the interior diaphragms(D2 to D6) along the east exterior sur-face of Girder M of the north span(see Fig. 3).

For each span, post-tensioning wasapplied to the seven CFCC strands intwo separate stages. The initial post-tensioning for interior Diaphragms D2through D6 consisted of applyingabout 307 kN (68 kips), or 50 percentof the total transverse post-tensioningforce [605 kN (136 kips)]. The post-tensioning force in the transversestrands at end Diaphragms D1 and D7consisted of applying about 87 kN(19.5 kips), also 50 percent of the totaltransverse post-tensioning force [175kN (39 kips)].

Fig. 15. Automated displacement transducer installed on Structure B.

Fig. 16. Typical strain gauge and SMS transducers on one of the four CFCC post-tensioning strands.

TRANSDUCER


The final transverse post-tensioningwas applied after the composite deckslab of the bridge was placed.

After the completion of all post-ten-sioning operations, a sidewalk on oneside of the bridge and a barrier railingon the other side were constructed.Next, a latex-modified surfacing mix-ture was installed over the top of thedeck. After completing the railing onthe sidewalk and performing a seriesof bridge load tests, Structure B wasopened to traffic (see Fig. 13).

INSTRUMENTATION ANDMONITORING

Because a bridge of this type hadnever been constructed before, theneed for instrumentation and remotemonitoring of critical parameters wereidentified early on. Monitoring thegirders would occur from fabricationthrough erection and continue for fiveyears thereafter. This program will ul-timately provide relevant informationon the serviceability of bridge struc-tures that use CFRP materials. OnlyStructure B instrumentation is dis-cussed in this paper. This section de-scribes the various aspects of the DTgirders responses during the variousconstruction stages.

All 12 DT girders were instru-mented and monitored during fabrica-tion to measure and document forcesand stress levels during prestressingoperations. In addition, six girderswere instrumented with both internaland external sensors for long-termmonitoring. These are identified inFig. 3. Most of the instrumentationwas installed during the fabrication ofthe girders at the precast facility. Theinstrumentation has the following ob-jectives for the five-year program.

1. Measure and monitor the preten-sioning load applied to the CFRPLeadline tendons.

2. Measure concrete strain distribu-tion in the girder cross section andtopping.

3. Measure girder camber and de-flections during girder fabrication andbridge construction sequence.

4. Measure forces in the post-ten-sioning CFCC strands during con-struction.

5. Monitor the strain status of exter-

nal transverse and longitudinalstrands.

Measurement of Pretensioning Forces

Pretensioning forces were measuredby a load cell installed between thefabricator’s stressing jack and the an-chorage (chuck) at the live end. In ad-dition, load cells were installed at thedead end of selected tendons to moni-tor the applied pretensioning forces.Seven load cells were installed be-tween the stressing bulkhead and thedead end anchorage chuck.

Measured pretensioning forces inLeadline tendons of the six instru-mented girders (Girders C, G, J, K, L,and M) were recorded at 15-minute in-tervals from the time that prestressingwas completed until the time of ten-don release, which typically spanned athree-day period. Three of the six non-instrumented girders (Girders E, F,and H) were monitored until all oftheir tendons were tensioned, whichtypically took three to four hours. Theremaining three non-instrumentedgirders (Girders A, B, and D) weremonitored until the time of concreteplacement.

Fig. 17. NEFMAC grid placed over the flange of DT girders prior to placement ofbridge deck slab.

Fig. 18. CFCC reinforcement cage for top concrete barrier (under handrail).

30 PCI JOURNAL

30 reference points were embedded inthe concrete surface along the topflange of the girders at midspan, thetwo quarter points, and near the ends.

The deflection at a particular crosssection was determined by measuringthe elevation of the reference pointsusing a precision level and surveyor’srod with high-resolution scale. Prior toreleasing the tendons, elevations foreach point were measured andrecorded and used as the zero refer-ence elevation for all subsequent mea-surements.

Midspan deflections were deter-mined by subtracting the measured el-evation at midspan from the averageelevation of the two end referencepoints. Similarly, quarter span deflec-tions were determined by subtractingthe measured elevation at the quarter-span from the average elevation of thetwo end reference points and the cor-responding end elevation. After finalconstruction of the bridge, the embed-ded reference points were transferredto the top deck. These stainless steelpoints were set just below the drivingsurface and covered with a protectivecap for future deflection measure-ments.

Automated Measurement of Deflection

For automated deflection measure-ment of DT girders, automated deflec-tion transducers were installed on thesix instrumented girders after erection(see Fig. 15). A taut high-strengthstainless steel wire was strung be-tween the two fixed anchorage pointsestablished near the ends of the girderto serve as a reference. Displacementtransducers were then installed alongone girder stem at the north quarterpoint, midspan, and south quarterpoint.

Measurement of Post-tensioning Forces

For the six instrumented girders, allfour CFCC strands were instrumentedwith load cells at one end. These wereinstalled between the anchorage nut onthe tendon sleeve and the bearing plateembedded in Diaphragm D6, near thenorth end of the girder (see Fig. 10).

Fig. 19. NEFMAC reinforcement for the barrier wall (looking down into theformwork from the top).

Fig. 20. CFRP Leadline and CFCC reinforcements for sidewalks.

Measurement of Concrete Strain

Embedded vibrating wire straingauges with an effective gauge lengthof 152 mm (6 in.) were installed tomeasure the strain distributions alongthe depth of the girder cross sections.These gauges were positioned at themidspan and quarter points of each ofthe six instrumented DT girders. Atotal of 30 strain gauges per girderwere installed. Of these, 21 were in-stalled in the precast girder section atthe precast plant, while the remainingnine gauges were installed in the cast-in-place deck slab at the bridge site.

Locations of these gauges are de-

picted in Fig. 14. In the figure, “Z” de-notes the DT girder designation, and“N” denotes the north end quarterpoint. Each vibrating wire strain gaugeincluded a thermistor for measuringthe concrete temperature associatedwith each strain measurement.

Measurement of Early Age Girder Deflection

To obtain a complete history ofearly age deflection in the six instru-mented girders, deflections were mea-sured at selected intervals from the in-stant of tendon release to thecompletion of construction. A total of


As mentioned previously, post-ten-sioning was applied in two distinctstages: 60 percent of the total desiredpost-tensioning force applied at theprecast plant just prior to shipping andthe remaining 40 percent applied atthe bridge site after placing the com-posite deck slab. The measured aver-age post-tensioning force in CFCCstrands after final post-tensioning was454 kN (102 kips).

It should be noted that the initial andfinal post-tensioning were each ap-plied in two operations. First, approxi-mately 50 percent of the desired post-tensioning force was applied bypulling the strands from the south end(see Fig. 10). The setup then moved tothe north end for the remaining 50 per-cent.

Monitoring the Status and Integrity of External CFCC Strands

To monitor the structural behaviorand long-term status/integrity of exter-nal CFCC post-tensioning strands ofthe six non-instrumented girders,strain gauges and displacement trans-ducers were installed on the four lon-gitudinal tendons of each girder. Thepurpose of these sensors is to deter-mine potential failure or loss of an-chorage in the external CFCC strands.Fig. 16 shows a typical transducer onone of the four CFCC strands. A totalof 21 strain gauges and three hybriddisplacement sensors (SMSTM)* wereinstalled on the 24 strands.

Placing the Bridge Deck Slab

After the 12 girders were erectedand grouted along the longitudinaljoints, the initial transverse post-ten-sioning was applied, and constructionof the deck slab began. For the deck,CFRP NEFMAC reinforcement wasinstalled over the top flange of thegirders (see Fig. 17). The nine remain-ing embedded concrete strain gaugesrequired at each instrumented girder,for the deck slab concrete strain mea-surements at midspan and the twoquarter point locations were installed.All the instrumentation cables wererouted through the sidewalk.

The NEFMAC reinforcement wassupplied in the form of grid sheets,precut to required shapes by the manu-facturer. Each grid sheet incorporatedlongitudinal reinforcement elementsspaced at 300 mm (11.8 in.) on centerand transverse elements spaced at 100mm (4 in.).

The sheets were supported on 25mm (1.0 in.) tall plastic slab bolsters,which were tied to both the slab bol-ster and girder using plastic ties, toprevent the sheets from floating duringconcrete placement. The deck slabwas cast using a minimum 75 mm (3in.) thick concrete topping with a min-imum 28-day compressive strength of38 MPa (5500 psi).

After the bridge deck slab, other es-sential components of the bridge –sidewalk, barrier railing, latex topping,and open parapet railing – were con-structed. The latex-modified concrete

* SMS is the trademark name of SMS034 hybrid displacement sensor.

Fig. 21. Variation of pretensioning force in CFRP Leadline tendons of Girder L.

Fig. 22. Variation of pretensioning force in CFRP Leadline tendons of Girder G.

topping wearing surface was of 38mm (1.5 in.) nominal thickness having28 day compressive strength of 52.2MPa (7560 psi).

Fig. 18 shows the CFCC reinforce-ment cage used for the open parapetrailing, and Fig. 19 shows the NEF-MAC reinforcement used for the con-crete barrier railing, constructed on theopposite side of the deck from thesidewalk. The sidewalk reinforcementconsists of a combination of straightCFCC and CFRP Leadline rods andbent CFCC strands (see Fig. 20). Con-crete compressive strengths for theseelements generally exceeded 51.9MPa (7520 psi).

MEASURED RESULTSDURING CONSTRUCTIONIn this section, measured tendon

forces, concrete strains, deflections,

32 PCI JOURNAL

and post-tensioning forces during theconstruction of the bridge are pre-sented.

Pretensioning Tendon Forces

Figs. 21 and 22 show the measuredforces in selected Leadline tendons ofGirders L and G, respectively, fromthe start of prestressing to the instantof release of prestressing forces.Girder L is located in the north span ofthe bridge, while Girder G is locatedin the middle span. Note that the lossof prestressing forces is not significantimmediately after the prestressing;however, significant loss in the forcesoccurs after about 40 hours of pre-stressing. This phenomenon could beattributed to introduction of heat re-sulting from hydration of the concrete.

As shown in the figures, the loss inprestressing forces is restored as thecuring proceeds and prior to the re-lease of the prestressing forces. It isfurther observed that the measuredprestressing forces, as expected, dropto zero upon release of the prestress-ing forces at the load cell location (seeFig. 9). The prestressed force releaseoccurred after 120 and 96 hours fromstart of prestressing in Girders L andG, respectively.

Concrete Strains

The measured concrete strains atmidspan of Girders C and G are pre-sented in Figs. 23 and 24, respectively.In these figures, letters “C” and “G”denote Girders C and G, respectively,while letter “M” refers to the midspansection of the girders. The strain val-ues are shown from the instant of re-lease of prestressing forces, throughinitial post-tensioning (August 15 to17, 2001), shipping, erection (August21 and 22), final post-tensioning ofCFCC longitudinal strands (September28), and addition of sidewalk and con-crete barrier railing. Strain valueswere taken as zero prior to release ofpretensioning forces.

As expected, compressive strainswere developed in the DT girders,while low tensile strains were devel-oped in the deck slab of the girdersafter final post-tensioning. Thesestrains are desirable as the prestress-induced compressive strains in the ten-

Fig. 23. Measured concrete strains at midspan of Girder C.

Fig. 24. Measured concrete strains at midspan for Girder G.

Fig. 25. Measured deflections for Girder K.

INITIAL LONGITUDINAL

POST-TENSIONING

AFTER RELEASE

OF TENDON


sion zone and tensile strains in thecompression zone will counteract thestrains due to service loads.

Deflections

Fig. 25 shows the early-age deflec-tions at midspan and quarter points ofGirder K. Early-age deflection refersto camber developed in the girderfrom the instant of release of preten-sioning forces to the completion ofconstruction of the bridge. From thefigure, note that the release of preten-sioning forces and application of post-tensioning forces result in camber ofabout 20 mm (0.79 in.). The maximumcamber occurred after the initial longi-tudinal post-tensioning, followed by aslight camber decrease after placingthe deck slab.

Post-tensioning Forces

Fig. 26 shows the forces in the fourexternal CFCC post-tensioning strandsin Girder J (one of the four north-endspan girders of the bridge). The initialand final post-tensioning cause the in-crease in the forces in the externalpost-tensioning strands in a stair-stepmanner. It is worth noting that thepost-tensioning forces remained al-most unaffected during constructionstages. A similar variation of theforces in transverse post-tensioningstrands at Diaphragms D2, D3, D4,D5, and D6 after initial and finaltransverse post-tensioning is illus-trated in Fig. 27.

CONCLUDING REMARKSThe Bridge Street Bridge Deploy-

ment Project has served as an extraor-dinarily successful example of tech-nology transfer from research anddevelopment to serviceable structure.The bridge exhibits innovation notonly in the material itself, but also inthe variety of prestressing methodsimplemented – pretensioning andpost-tensioning, internal and external.

Extensive instrumentation and con-tinuous remote monitoring have pro-vided valuable technical informationduring various construction stages andwill continue to do so over the five-year monitoring period. The findings ofthe full-scale girder test at CTL and the

Fig. 26. Typical measured forces in longitudinal CFCC strands (Girder J).

Fig. 27. Typical measured forces in transverse CFCC strands (north span).

continuous monitoring of this proto-type bridge have confirmed the designassumptions made during the develop-ment of the construction documents.

This project won the Harry H. Ed-wards Industry Advancement Awardin the recent PCI Design Awards Pro-gram. The jury citation was as fol-lows:

“The use of CFRP tendons in pre-cast concrete bridges opens new po-tential for bridge designers to solvedesign problems more effectively andwith faster construction. The carefuland detailed work undertaken by this

team of researchers, designers, andcontractors holds great promise forfuture construction using CFRP. Thisproject takes existing components andmaterials and expands on their abili-ties in new ways that will benefit theindustry overall. These attributes de-fine a Harry H. Edwards award win-ner.”

A large monument and plaqueadorns the bridge on the west side ofthe north end approach (see Fig. 28).Fig. 29 is a group picture showingsome of the officials and participantsat the dedication ceremony.

FINAL TRANSVERSE

POST-TENSIONING

34 PCI JOURNAL

CREDITSResearch, Development & Design

Consultant: Civil Engineering De-partment, College of Engineering,Lawrence Technological University,Southfield, Michigan

Designer: Hubbell, Roth & Clark, Inc.,Bloomfield Hills, Michigan

Precaster: Hollowcore Incorporated/Prestressed Systems, Inc., Detroit,Michigan

General Contractor: Angelo IafrateConstruction Company, Warren,Michigan

Owner: City of Southfield, Southfield,Michigan

ACKNOWLEDGMENTSThe success of this project is due to

the energy and talent of many people,each of whom played a significantrole. These include various re-searchers, designers, manufacturers,suppliers, and builders. The innumer-able contributions made by individualsand the people representing variouscompanies are recognized here andgratefully acknowledged: HollowcoreIncorporated/Prestressed Systems,Inc., Windsor, Ontario, Canada, whofabricated all the precast girders andperformed all post-tensioning opera-tions; Construction Technology Labo-ratories, Inc., Skokie, Illinois, whoprovided instrumentation and testingof the full-scale test model and bothbridges; Autocon Composites,Toronto, Canada, the manufacturers ofthe CFRP reinforcement NEFMAC;ABM Corporation, New York City,and Sumitomo of America at their SanFrancisco office, who served as thetrading company; Mitsubishi Chemi-cal Functional Products, Inc., andVantec Co., Ltd. (Komatsu Indus-tries), the supplier and manufacturer,respectively, of the Leadline tendons;Mitsui & Co. (USA), Inc., Cleveland,Ohio, who served as the trading com-pany, and Tokyo Rope Mfg. Co., Ltd.,the supplier and manufacturer of thespecial cable reinforcement CFCC;Dr. George Abdel-Sayed, ProfessorEmeritus from the University ofWindsor, who served as a special con-sultant to Hubbell, Roth & Clark; theresearch team (undergraduate, gradu-

Fig. 28.Monument withcast bronzeplaque unveiledat thededication.

OWNER EPILOGUEThe City of Southfield’s new Bridge

Street Bridge replaces a structurally ob-solete steel bridge. The project consistsof two parallel reinforced concretebridges that are located at the only ac-cess point to the Bridge Street IndustrialPark, an important commerce center inthe city. One bridge was built usingstandard AASHTO Type III precastconcrete I-girders with conventionalsteel reinforcement and a new substruc-ture. The second was constructed usingthe existing piers and abutments and 12precast concrete double tee (DT) girdersreinforced with carbon fiber reinforcedpolymer (CFRP) material. This structureis the first known multi-span concretehighway bridge in the world to incorpo-rate this material as its principal struc-tural reinforcement.

This pioneering achievement wasmade possible only through the com-bined talents of many, including thosefrom the Japanese composite materialmanufacturing industry and domesticacademic research. The design and con-

struction was brought to fruition withoutthe benefit of any established national orinternational standards for a structure ofthis type, which required an extraordi-nary effort and innovation by the Cityand project partners. The completedwork represents the culmination of morethan ten years of research and develop-ment, during which time many potentialsolutions to this nation’s serious trans-portation problem were considered anddiscarded before this CFRP bridge solu-tion became a reality.

The City of Southfield is proud of theBridge Street Bridge project, both for itscreative and innovative use of state-of-the-art CFRP construction technologyand for the prestige that the project hasbrought to the city. It is also proud ofthe dedication, courage, and hard workdemonstrated by the project team in de-veloping and building this major munic-ipal infrastructure project.

– Wayne BonusCity of Southfield


ate, and post-doctorate students) of thecivil engineering department atLawrence Technological University inSouthfield, Michigan; Hubbell, Roth& Clark, who performed the designand construction engineering, inspec-tion and materials testing, and supportgroups; and the National ScienceFoundation, who funded the originalresearch upon which the project de-sign concept was based.

Site construction was funded in the1998 fiscal year through FHWA asone of the TEA-21 High Priority Pro-jects. Instrumentation and monitoringfunding was provided under the Inno-vative Bridge Research and Construc-tion Program of TEA-21. The BridgeStreet Subdivision property ownersgranted approval of a Special Assess-ment District. The Tax Increment Fi-nance District was created by the City.

The Michigan Economic Develop-ment Corporation awarded a grant.Congressional support came fromMichigan Representatives JosephKnollenberg and Sander Levin. Fi-

REFERENCES1. ACI Committee 440, “State-of-the-Art Report on Fiber Rein-

forced Plastic Reinforcement for Concrete Structures,” ACI440R-96, American Concrete Institute, Farmington Hills, MI,1996, 153 pp.

2. Rizkalla, S. H., “A New Generation of Civil EngineeringStructures and Bridges,” Proceedings of the Third InternationalSymposium on Non-metallic (FRPRC) Reinforcement forConcrete Structures, Sapporo, Japan, V. 1, October 1997, pp.113-128.

3. Dolan, C. W., “FRP Prestressing in the U.S.A.,” Concrete In-ternational, V. 21, No. 10, October 1999, pp. 21-24.

4. Tadros, G., “Provisions for Using FRP in the Canadian High-way Bridge Design,” Concrete International, V. 22, No. 7,July 2000, pp. 42-47.

5. Grace, N. F., Abdel-Sayed, G., Sakla, S., and Wahba, J., “Fi-nite Element Analysis of Bridge Street Bridge, City of South-field, Michigan,” LTU Research Project No. 36, Report Sub-mitted to Hubbell, Roth & Clark Consulting Engineers, 1997,Bloomfield Hills, MI.

6. Grace, N. F., and Abdel-Sayed, G., “Double Tee andCFRP/GFRP Bridge System,” Concrete International, V. 18,No. 2, February 1996, pp. 39-44.

7. Grace, N. F., and Abdel-Sayed, G., “Ductility of PrestressedBridges Using CFRP Strands,” Concrete International, V. 20,No. 6, June 1998, pp. 25-30.

8. Grace, N. F., and Abdel-Sayed, G., “Behavior of ExternallyDraped CFRP Tendons in Prestressed Concrete Bridges,” PCIJOURNAL, V. 43, No. 5, September-October 1998, pp. 88-101.

9. Grace, N. F., “Continuous CFRP Prestressed Concrete

Bridges,” Concrete International, V. 21, No. 10, October1999, pp. 42-47.

10. Grace, N. F., Abdel-Sayed, G., Wahba, J., and Sakla, S.,“Mathematical Solution for Carbon Fiber Reinforced PolymerPrestressed Concrete Skew Bridges,” ACI Structural Journal,V. 96, No. 6, November-December 1999, pp. 981-987.

11. Grace, N. F., and Abdel-Sayed, G., “Behavior of Carbon FiberReinforced Prestressed Concrete Skew Bridges,” ACI Struc-tural Journal, V. 97, No. 1, January-February 2000, pp. 26-34.

12. Grace, N. F., “Response of Continuous CFRP Prestressed Con-crete Bridges Under Static and Repeated Loadings,” PCIJOURNAL, V. 45, No. 6, November-December 2000, pp. 84-102.

13. Grace, N. F., “Transfer Length of CFRP/CFCC Strands forDouble-T Girders,” PCI JOURNAL, V. 45, No. 5, September-October, 2000, pp. 110-126.

14. Grace, N. F., Enomoto, T., and Yagi, K., “Behavior of CFCCand CFRP Leadline Prestressing Systems in Bridge Construc-tion,” PCI JOURNAL, V. 47, No. 3, May-June 2002, pp. 90-103.

15. Grace, N. F., and Abdel-Sayed, G., “Evaluation ofCFRP/CFCC Full-Scale DT Girder, Part 1: ExperimentalStudy,” Submitted to PCI JOURNAL, 2002.

16. Grace, N. F., and Abdel-Sayed, G., “Evaluation ofCFRP/CFCC Full-Scale DT Girder, Part 2: Analysis,” Submit-ted to PCI JOURNAL, 2002.

17. Mitsubishi Chemical Corporation (MCC), Leadline CarbonFiber Tendons/Bars, Product Manual, 1994.

18. Tokyo Rope Mfg. Co. Ltd., Technical Data on CFCC, ProductManual, 1993.

nally, the Mayor of the City of South-field, the City Council, and the admin-istration are commended for their vi-

sion of the future and their courage toventure into this unconventional con-struction arena.

Fig. 29. Nabil F. Grace (fourth from left) with Southfield Mayor Brenda Lawrence(third from right), Shigeto Tanaka (second from right), President of Tokyo Rope Mfg.Co., Ltd., and representatives of Mitsui & Co. at the Bridge Street Bridge Dedication.

Documents

Design-Construction of Bridge Street Bridge – First CFRP