ase10 5 bank

Pultruded FRP Plank as Formwork and Reinforcementfor Concrete Members

by

Lawrence C. Bank, Michael G. Oliva, Han-Ug Bae, Jeffrey W. Barkerand Seung-Woon Yoo

Reprinted from

Advances in Structural EngineeringVolume 10 No. 5 2007

MULTI-SCIENCE PUBLISHING CO. LTD.5 Wates Way, Brentwood, Essex CM15 9TB, United Kingdom

ASE 10-5_Bank 15/10/07 11:46 am

1. INTRODUCTIONIn the past decade there have been numerous applicationsof FRP composite materials as internal reinforcements(typically in the form of FRP rebars) for concretestructures (ACI 2006). FRP reinforcing materials aregenerally used to prevent corrosion in reinforced concretestructures that plague conventional steel reinforcedconcrete structures. In addition there have beenwidespread applications of bonded FRP materials forrepairing or strengthening concrete structures. The use ofhybrid FRP/concrete members with a dual purpose ofboth formwork and reinforcement, has been considered

in some studies and has been applied in a small numberof bridge decks (Deskovic et al. 1995; Hall and Mottram1998; Hullat et al. 2003; Dieter et al. 2004; Matta et al.2006; Cheng et al. 2005; Berg et al. 2006). A combinedformwork and reinforcement system can facilitate rapidconstruction of concrete members since no conventionalformwork is needed, which requires time consumingassembly and dismantling. In order for a smoothpultruded FRP plank to act compositely with theconcrete, the surface of the FRP plank needs to be treatedto increase its bond properties.

This particular study was primarily motivated by thedesire to use a commercially produced pultruded FRP

Advances in Structural Engineering Vol. 10 No. 5 2007 525

Pultruded FRP Plank as Formwork and Reinforcement

for Concrete Members

Lawrence C. Bank1,*, Michael G. Oliva1, Han-Ug Bae1, Jeffrey W. Barker1

and Seung-Woon Yoo2

1Department of Civil and Environmental Engineering,University of Wisconsin, Madison, WI 53706, U.S.A.

2 Department of Civil Engineering,Kwandong University, Kangwon 215-802, Korea

(Received: 21 November 2006; Received revised form: 29 June 2007; Accepted: 18 July 2007)

Abstract: A feasibility study in which the use of a commercially produced pultrudedfiber reinforced polymer (FRP) plank for both permanent formwork and secondary orprimary tensile reinforcement of a concrete structural member is described in thispaper. To achieve satisfactory bond at the interface between the smooth surface of theFRP plank and the concrete, two kinds of aggregate, gravel and sand, were epoxybonded to the planks. Concrete beams using the aggregate-coated FRP planks werefabricated and tested. Satisfactory bond between the FRP plank and the concrete wasdeveloped which was evidenced by numerous well-distributed flexural cracks, andultimate capacities of the aggregate coated FRP plank specimens greater than the steelrebar reinforced control specimen. ACI 440 equations were found to provide goodpredictions of the flexural strengths but poor predictions of the shear strengths of theFRP plank reinforced beams. ACI 318 equations, however, provided good shearstrength predictions.

Key words: pultrusion, fiber reinforced polymer, formwork, reinforcement, concrete structures, aggregate coating,bridge decks.

* Corresponding author. Email address: [email protected]; Fax: +1-608-262-5199.

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Pultruded FRP Plank as Formwork and Reinforcement for Concrete Members

526 Advances in Structural Engineering Vol. 10 No. 5 2007

plank as a stay-in-place form and for secondaryreinforcement for flexural crack control in a new bridgedeck that was constructed without any reinforcing barsin the concrete deck (also known as “reinforcement-free” or “steel-free”) in Black River Falls, Wisconsin,USA in June and July 2007. The deck was supported onwide-flange bulb T precast concrete girders at 2.1 mspacing that had a 914 mm gap between edges of theflanges. A number of reinforcement free decks havebeen constructed in Canada in recent years based on thephilosophy of “arching action” in the decks (Newhookand Mufti 1996; Bakht and Lam 2000). It has beenshown that the ultimate failure mode of these decks ispunching shear and not flexure. In these designs nonegative moment reinforcing is provided in the slab overthe girders, however, fiber reinforced concrete istypically used to control shrinkage cracking in thedeck. Nevertheless, it has been found that unsightlylongitudinal cracks have developed on the undersides ofthe slabs between the girders in these decks underservice loads (Bakht and Lam 2002). This has led to theuse of secondary transverse reinforcement (typicallyusing FRP bars) to distribute the flexural cracks in thedecks. An objective of this study was to determine if theFRP plank was able to serve as the stay-in-place form aswell as control the flexural cracking in a reinforcementfree deck, thus relieving the requirement for thesecondary crack control reinforcement. A complementarymotivation for the study was to determine if the FRPplank could serve as the primary tensile reinforcementof the deck if this was necessary for a deck design thatrequired non-metallic reinforcing bars for transverseflexural strength to resist positive bending momentbetween the girders. In this case it is expected thatconventional steel or FRP reinforcing bars would beused to carry negative moment in the deck.

In this feasibility study, an inverted portion of acommercially available FRP plank having integral

T-shaped ribs, shown in Figure 1, was used as theformwork and the reinforcement for the concrete. TheFRP plank is produced in 305 and 610 mm widths andis used in walkway or flooring applications with the flatside facing up and has a smooth inner surface. (Silicasand grit is often applied to the flat surface of the plankto create a non-slip walking surface). Two types of stoneaggregate, sand and gravel, were bonded to the inner flatsurface of planks to improve the bond between theconcrete and the FRP plank. The aggregate was bondedwith epoxy to the FRP plank, which was cured, prior tothe placement of the concrete. No other flexural or shearreinforcement was used in the beams. Two controlspecimens were also tested. One control had noaggregate bonded to the FRP plank and the other hadinternal steel main reinforcing bars instead of the FRPplank. Depending on the length of the beam, shear orflexural failures occurred.

Two other options to achieve the composite actionbetween the FRP plank and the concrete were considered.One was to apply epoxy to the surface of the FRP plankand to place the concrete on the FRP planks beforeepoxy cured. This option was felt to be unrealistic forfield applications for which the FRP plank is intended,as there is insufficient time to coat the formwork withepoxy during the deck casting and finishing operations.In addition, the use of a liquid epoxy system would notallow the workers to stand on the forms during the deckpour which would make the casting operation almostimpossible. This was confirmed during the pouring ofthe bridge deck in Black River Falls shown in Figure 2.The need for the workers to stand on the forms betweenthe deck during the casting is evident. The other methodconsider to develop bond was to use FRP cross rodsinserted through the webs of the FRP plank (similar toFRP grating construction). This option was attempted in

Figure 1. 12 inch wide pultruded FRP plankFigure 2. Casting of concrete bridge deck using pultruded FRP

planks as formwork and secondary reinforcing

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Lawrence C. Bank, Michael G. Oliva, Hang-Ug Bae, Jeffrey W. Barker and Seung-Woon Yoo


a previous study (Ringlestetter et al. 2006) but wasfound to be difficult and costly to implement in theshop. Therefore, bonding the aggregate to the surface ofFRP plank prior to the placement of concrete wasselected as the preferable option for this study.

The feasibility of using this system was investigatedexperimentally using beams of different lengths thatwere tested in three point bending. The test resultsfrom the FRP plank specimens were compared to codepredictions and to the results obtained from the controlspecimens.

2. FABRICATION OF SPECIMENSFive 230 mm wide by 178 mm deep beams (specimens 1-5) with different lengths (three beams with a 1.09 m spanand two beams with a 1.83 m span) were fabricated usingthe aggregate coated FRP plank as the bottom formworkfor the concrete (see Table 1 for details). No othertensile or shear reinforcement was used in the beams.Longitudinal tension tests were conducted on the FRPplank material yielding a longitudinal tensile strength,σL = 481.3 MPa and a longitudinal modulus of elasticity,EL = 26,890 MPa (Ringelstetter et al. 2006). Figure 3shows the approximate cross sectional dimensions of atwo-legged portion of the FRP plank that was used in thetests. The 203 mm wide portion, shown in Figure 3, wascut from the center portion of the 305 mm wide FRPplank, shown in Figure 1, to produce a representative unitwidth element of the FRP plank reinforced beam. Figure 4

shows the dimensions of the specimens.The first step in the fabrication was to cut the FRP

planks to the appropriate dimensions. Thereafter, aconstruction-grade epoxy (Concressive 1090) wasspread on the top (inner) surface of the inverted plank.Epoxy was only placed between the ribs of the plank onthe horizontal surface. No epoxy or aggregate wasbonded to the protruding vertical ribs on either theflanges or the webs of the ribs. The epoxy was placeddirectly on the as-received pultruded material whichwas not roughened or sanded. The gravel or sand wasscattered on the wet epoxy using a perforated bucket tocover approximately 30% of the total area. To ensurethat the top surface of the aggregate was not covered byepoxy a thin layer of epoxy was used. Sizes of theaggregates were 3.18 to 6.35 mm for the gravel and 1.59to 2.54 mm for the sand. Figure 5 shows the aggregatecoated FRP planks. Plywood forms were thenconstructed around the FRP planks to form the sides ofthe beam specimens which were then cast usingconcrete from a local ready-mix commercial concretevendor. A Wisconsin Department of TransportationGrade D, Size 1 (19 mm max. aggregate size) concretedesign mix, having a 28-day target compressive strengthof 27.6 MPa, was specified for all test specimens.

Two 203 mm wide by 178 mm deep beams(specimen C1 and C2) were also fabricated as controlspecimens for comparison. One of the controlspecimens, C1, had a length of 1.09 m was fabricated

25

3

3

102 102

54

25

51

Figure 3. Approximate cross-sectional dimensions of potion of

FRP plank used in test beams (dimensions in mm)

Span 203

178

FRP plank

Figure 4. Dimension of fabricated FRP plank reinforced beam

specimens (dimensions in mm)

Figure 5. Aggregate coated FRP planks

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using the FRP plank as formwork, but no aggregate wasbonded to the top of the FRP plank. This controlspecimen served as the control for FRP plank specimens1-3 and was intended to show the difference between thespecimens with and without the aggregate when testedover short spans that would be shear dominated. Theother control specimen, C2, was a conventional steelreinforced concrete beam with a 1.83 m span, with noshear reinforcement and no FRP plank. The beam wasreinforced with three 10 mm diameter steel rebars (414MPa nominal yield strength) with 38 mm of clearbottom cover. This reinforcement quantity was theamount required for the bottom flexural transversereinforcement in the Black River Falls bridge deck whena conventional flexural design approach according toAASHTO is used (AASHTO 2007). The clear spanbetween girders for the bridge was 914 mm. Thiscontrol specimen was used to compare the performanceof the FRP plank beam to that of a conventional steelreinforced beam of a longer span whose failure wasexpected to be flexurally dominated. The purpose of thisinvestigation was to see if the aggregate coated FRPplank could serve as the positive moment reinforcementfor the bridge deck, both from a strength (i.e., capacity)and a serviceability (i.e., crack control) perspective.Details of all the fabricated beams including controlspecimens are summarized in the Table 1.

3. EXPERIMENTAL SETUP ANDINSTRUMENTATION

The beam test specimens were placed on two steelbearing plates 51 mm wide in a simply supportedconfiguration. The center-to-center spacing of thebearing plates was either 1.09 m (specimens 1-3 and C1)or 1.83 m (specimens 4-5 and C2). A steel roller wasplaced under the center of each bearing plate to allowrotation at the supports. Deflections were recorded withlinear variable differential transformers (LVDTs) at the

center of the specimen. A load cell on the head of thehydraulic actuator measured loads during theexperiments. Longitudinal strains of the FRP plank andthe concrete top surface were measured using electricalresistance strain gauges. The strain gauges were offset89 mm in the longitudinal direction from the center ofthe beam to avoid interfering with the load head. Figure 6shows typical experimental instrumentation used for thetesting.

The load was applied at the center of the specimen ina three point bend test configuration by a hydraulicactuator under manual displacement control. A 76 mmwide steel plate was placed at the bottom of the loadinghead. Gypsum cement was cast between the loaded topsurface of the specimen and the steel plate to transferload uniformly along the center line of the specimen.Figures 7 and 8 show the test setup for the specimens 1and 4, respectively.

4. EXPERIMENTAL RESULTS4.1. Comparison Criteria

Three criteria were selected to evaluate the compositeaction between the FRP plank and the concrete duringthe experiments. The first criterion was the initialcracking load of the specimen because cracking is animportant service load design criterion for bridgedecks. This was obtained from observations of thechanges in the strain gauge readings and the deflectionreadings during the test. The second criterion was thedistribution of flexural cracks. In bridge decks it ispreferable to have numerous small cracks that won’tlead to deterioration, rather than a few large cracks.Flexural (and shear) cracks were marked and countedduring the experiments. It was expected that the bondbetween the FRP plank and the concrete provided bythe aggregate coating would result in closely spacedflexural cracks having small widths would occur asopposed to a few wide and sparsely-spaced cracks.

Table 1. Details of the fabricated beams

Compressive

Specimen Span strength, f ′cI.D. (m) Tensile Reinforcement Type (MPa)

1 1.09 Gravel coated FRP plank 25.82 1.09 Sand coated FRP plank 25.83 1.09 Sand coated FRP plank 24.5C1* 1.09 FRP plank 25.84 1.83 Sand coated FRP plank 32.15 1.83 Sand coated FRP plank 33.5C2* 1.83 Steel reinforcement (3-D10) 32.9

*Control specimen

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The third criterion was the capacity of the specimen andits failure mode, which was anticipated to be either aflexural mode for the long beams or a shear mode forthe short beams.

4.2. Initial Cracking Capacity

The initial flexural cracking load was identified byobserving the change in slope of the load-strain curves.The load at first cracking obtained from the strain gagedata was typically less than the cracking load obtainedby visual observation. The initial cracking loads and thestrains at the initial cracking loads are shown in Table 2.All the initial cracks were observed near the center ofthe specimens. The loads obtained from each test wereconverted to give the cracking moment and normalizedwith respect to a 27.6 MPa compressive strengthconcrete to account for the differences in the strengthsof the concrete. The normalization was performed by

multiplying the calculated moment by .The beams (specimens 1-5) with the aggregate coated

FRP planks showed higher initial cracking capacitiescompared to the control specimen reinforced by the FRPplank with the smooth surface (specimen C1) andcompared to the specimen with the steel reinforcing bars(specimen C2). This indicates that a coated FRP plankcan produce an increase in the initial cracking momentcapacity of a concrete beam, which may provide aserviceability benefit for a reinforced concrete section,particularly a bridge deck. The beams with the sandcoated FRP plank (specimen 2 and 3) showed higherinitial cracking capacity than the specimen with the

gravel coated FRP plank (specimen 1), indicating thatsand coating may provide a better interfacial bondmechanism than the gravel. However, as only one gravelcoated beam was tested no statistically conclusivedifference between the sand and gravel coated specimenscan be deduced from these results.

4.3. Distribution of Flexural cracks

Current design codes allow a concrete structure to crackunder service loads, however, the width of the cracks istypically limited to a prescribed value or otherwisecontrolled by reinforcing spacing requirements. Since alarger number of cracks will lead to narrower crackwidths for each crack, a comparison of the number offlexural cracks in the specimens was an importantevaluation criterion in this study

The number of the flexural cracks was counted afterthe failure of each specimen (Table 2). In the shortbeams, 9-11 small flexural cracks occurred in theaggregate coated case (specimens 1-3) and only 3 largecracks occurred in the case without the aggregate coating(specimen C1). This clearly shows that aggregatecoating provides a mechanism to transfer bond stressesat the interface between the FRP plank and the concreteto distribute the cracks. The gravel coated beam(specimen 1) showed slightly better performance thanthe sand coated beams (specimen 2-3). Maximum crackwidth versus load for the short beams are shown inFigure 9. In the long beams (specimens 4 and 5), 22-29flexural cracks were measured. This was similar to thatof the steel control beam (specimen C2) as shown inTable 2. This demonstrates that the aggregate coatedFRP plank can serve as an effective tensile reinforcementand can distribute flexural cracks in a similar manner tointernal steel reinforcements.

4.4. Capacities and Failure Modes

The specimens with the aggregate coated FRP planksfailed in a number of different modes. The failure modes

′fc 27 6. MPa

Figure 6. Typical instrumentation for tested specimens

Figure 7. Experiment setup of specimen 1 prior to loading

Figure 8. Experiment setup of specimen 4 prior to loading

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Figure 9. Crack widths versus load for short beams

Table 2. Test results

# of

Initial Deflection flexural

cracking Normalized initial at failure cracks

Specimen Span load cracking Failure load load at both Failure

I.D. (m) (kN) momenta(kN-mm) (kN) (mm) side mode

1 1.09 15.6 4,395 63.2 3.56 11 Shear2 1.09 20.9 5,909 66.7 4.22 9 Shear3 1.09 22.2 6,451 57.4 4.22 9 ShearC1 1.09 15.1 4,271 160.9 0.43 3 Flexural

(40.9b) (15.3b)4 1.83 12.5 5,276 59.6 16.99 22 Hybrid5 1.83 12.0 4,983 65.8 17.91 29 HybridC2 1.83 8.0 3,356 38.3 54.48 22 Flexural

(27.8c) (8.56c)

Measured strain at initial Measured strain at

cracking load failure load

(µε) (µε)

Specimen Concrete FRP Concrete FRP

I.D. (Compression) (Tension) (Compression) (Tension)

1 −74 37 −740 3,0002 −164 179 −812 4,2033 −180 176 −802 3,621C1 −100 139 −187 619

(−499b) (2835b)4 −197 151 −2,091d 6,6105 −188 243 −3,047 6,496C2 −112 - −3,804

(−1,038c) -

aNormalized with respect to concrete with 27.6 MPa compressive strengthbValue given for secondary peakcValue given for yield loaddConcrete crushing did not occur in the gauge location and hence the gage showed a lower value than at the failure location.

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were shear failure for specimens 1-3, flexural failure witha significant slip at the interface of the FRP plank and theconcrete for specimen C1, flexural/shear failure forspecimens 4-5 and flexural failure with yielding of thesteel rebars followed by concrete crushing for specimenC2. Capacities of the tested specimens are listed in Table 2.Figures 10 and 11 show the specimens after the tests,Figures 12 and 13 show the load vs. defection curves forthe tested specimens and Figures 14 and 15 show the load

vs. strain curves for the tested specimens. As can be seenfrom Table 2, the control specimens showed less capacitythan the aggregate coated FRP plank specimens. Themoment capacities of the short beams at cracking (4,395,5,909, 6,451, and 4,271 kN-mm)) can be compared withthe design service load moment for the Black River Fallsbridge which (4,316 kN-mm) which was calculated usinga AASHTO LRFD (2007) truck loading with a unit stripwidth for a clear span of 914 mm.

(a) Shear failure of specimen 1

(b) Shear failure of specimen 2

(c) Shear failure of specimen 3

(d) Flexural failure of specimen C1

Figure 10. Specimens 1-3 and C1 after test

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Distributed flexural cracks occurred during the initialloading stages of specimens 1-3. As the load approachedthe maximum value, a number of the flexural cracksdeveloped into diagonal shear cracks. Finally a criticaldiagonal shear crack formed that lead to the beams failingin shear, as seen in Figures 10 (a)-(c). Partial debondingbetween the FRP plank and the concrete was observed atthe midspan during the tests for all the beams. However,there was no evidence of any slip of the FRP plank fromthe concrete at the end of the beam following the shearfailure of the specimens. The compressive and tensilestrain levels recorded by the strain gauges (less than 0.001for concrete in compression and 0.0045 for FRP intension) are evidence that there was no concrete crushingor FRP tensile failure at the ultimate load.

The control specimen for specimens 1-3 (specimenC1) failed in a flexural mode with slip between the FRPplank and the concrete. A single wide flexural crack thatpropagated almost to the top of the beam occurred atmidspan can be seen in Figure 10 (d). When specimen C1was loaded after reaching its first peak, it continued toresist additional load and a secondary peak was seen. Thissecondary load carrying regime seemed to be due to theflexural resistance of the FRP plank itself with some forcetransfer to the concrete due to friction and the shape of the

plank. No shear cracks were observed in the specimen.The specimen was felt to have lost its fully compositeaction at the first load peak due to the previously notedslip. The first peak load was, therefore, selected as anultimate capacity of this specimen. The load deflectioncurves of the 1.09 m beams are shown in Figure 12.

Specimens 4-5 failed in a hybrid mode of shear andflexure at the failure load, after the occurrence of thedistributed flexural cracking. This failure mode was feltto have occurred since a significant diagonal crackdeveloped simultaneously with visible concrete crushingnear the loaded area, as seen in Figures 11 (a) and (b).This can also be classified as a shear-compressionfailure. At failure the compressive strain level at the topsurface of the concrete was close to or greater than 0.003which is generally accepted to be near the failure strainof concrete in compression. The control specimen(specimen C2) for specimens 4-5 failed in a flexuralmode with yielding of steel reinforcement followed bycrushing of concrete which is the typical failure mode ofan under-reinforced steel reinforced beam, as seen inFigure 11 (c). The ultimate capacity for the specimen C2was 58~64% of specimens 4 and 5 and demonstrates thatthe aggregate coated FRP plank can be used as tensilereinforcement instead of the steel reinforcement for a

(a) Hybrid failure mode of specimen 4

(b) Hybrid failure mode of specimen 5

(c) Flexural failure of specimen C2

Figure 11. Specimens 4-5 and C2 after test

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beam designed to achieve the capacity of the steelreinforced beam. It can be seen from the load-deflectionplot in Figure 13 that even though the load at failure inthe FRP plank beam at failure was larger than that of thesteel reinforced beam at failure, the deflection at failurein the steel reinforced beam was much larger than that ofthe FRP plank reinforced beam. This phenomenon of ahigher load carrying capacity and a lower deformabilityin FRP reinforced beams is a result of the linear elasticnature of FRP reinforcing materials and is accounted forin FRP design codes (ACI 2006).

5. COMPARISON OF EXPERIMENT TOCODE PREDICTION

Test results were compared to current ACI 318 and ACI440 code predictions and listed in Table 3. Comparisonwith the AASHTO bridge design code was not possiblesince the current AASHTO code does not haveprovisions for FRP reinforcements. The prediction ofthe capacities from the code equations was performedbased on assumptions that FRP plank did not cause anincrease in the cracking load of the beams and that fullcomposite action existed between the FRP plank and

Figure 12. Load-deflection plots for specimens 1-3 and C1

Figure 13. Load-deflection plots for specimens 4-5 and C2

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the concrete. ACI 318 predictions for the crackingcapacity were conservative except for the steel reinforcedspecimen C2. Compared to the experimental results,ACI 318 equations for shear capacity of the beamspredicted better values than those of ACI 440. The ACI440 equation for the shear capacity is a function of thedistance from extreme compression fiber to the neutralaxis in the cracked elastic section while ACI 318

equation for the shear capacity is a function of thedistance from extreme compression fiber to the centroidof the tensile reinforcement. When using ACI 318 orACI 440 for the calculation of the shear and flexuralcapacities of the FRP plank reinforced beams theresultant tensile force in the FRP was assumed to beapplied at the centroid of the FRP section which waslocated at a height of 12.78 mm from the bottom of the

Figure 14. Load-strain plots for specimens 1-3 and C1 Figure 15. Load-strain plots for specimens 4-5 and C2

Table 3. Comparison of the test results to code predictions

Initial cracking

load Failure load

(kN) (kN)

ACI 318 ACI 440 ACI 440

Specimen (Shear (Shear (Flexural

I.D. Test ACI 318 Test failure) failure) failure)

1 15.6 12.5 63.2 56.5 36.5 109.4(Shear failure)

2 20.9 12.5 66.7 56.5 36.5 109.4(Shear failure)

3 22.2 12.0 57.4 55.2 36.0 105.4(Shear failure)

C1 15.1 12.5 16.9 NA NA 12.5a

(Flexural failure)4 12.5 8.5 59.6 63.2 38.7 75.6

(Hybrid failure)5 12.0 8.5 65.8 64.5 39.1 77.4

(Hybrid failure)C2 8.0 8.5 38.3 52.0 - 24.5b

(Flexural failure)

a For C1 the flexural failure load is taken as the cracking load per ACI 318 or 440.b Calculated with the assumption of full composite action between the FRP plank and concrete. For C2 the flexural capacity was calculated using ACI 318.

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plank. The total area of the FRP plank in the 203 mmwide portion was 1,339 mm2. The design strength andthe design modulus were taken as, ffu = 481.3 MPaand Ef = 26,890 MPa respectively (i.e., no environmentalor resistance factors were used in the calculations and the average strength was assumed to be theguaranteed strength obtained from testing of theFRP). All the FRP plank beams were over-reinforcedbeams in flexure.

6. CONCLUSIONSA feasibility study was performed to investigate if anaggregate coated FRP plank could serve as both a stay-in-place form and either secondary or primary tensilereinforcement for a concrete beam. The aggregate coatedFRP plank reinforced beams performed as well or betterthan a steel reinforced control beam in terms of initialcracking moment capacity, the ability to distributeflexural cracks, and the ultimate load carrying capacity.The epoxy bonded aggregate coating at the surface of theFRP plank was essential for developing compositeaction. The use of the FRP plank without the surfacetreatment as a tensile reinforcement showed significantslip between concrete and the FRP plank, no distributedcracking and considerably less capacity. Sand and gravelaggregate were used in this study and both were found tobe acceptable. Comparisons with code predictionsindicated that the ACI 440 design guide provides anacceptable method to predict the flexural capacity ofaggregate coated FRP plank reinforced beams, whileACI 318 provides an acceptable method to predict theirshear capacity. Since it has been demonstrated that theaggregate coated FRP plank can be used as both asecondary and primary tensile reinforcement, itsconstructability advantages as a stay-in-place form canalso be realized. This will lead to construction efficiencyand may also produce a more durable bridge deck.While this study only included a small number ofspecimens and no definitive statistical conclusions canbe reached from the results they were sufficientlyconvincing to enable the use of a FRP plank stay-in-place form and reinforcement system in a pilotreinforcement free bridge deck that was constructed inWisconsin in 2007.

ACKNOWLEDGEMENTSFunding for this project was provided by the FederalHighway Administration (FHWA) through theInnovative Bridge Research and Construction Program(IBRC) and by the Wisconsin Department ofTransportation (WisDOT). Special thanks are due toFinn Hubbard and Scot Becker of WisDOT and toStrongwell for supplying the FRP materials for the study.

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pp. 183–189.

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