Steel Free Hybrid Reinforcement System for Concrete Bridge Decks ...

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ACKNOWLEDGEMENTS The authors from both the University of Missouri-Columbia (UMC) and the University of Missouri-Rolla (UMR) would like to gratefully acknowledge financial support from the Missouri Department of Transportation (MoDOT) for the research project. UMR researchers would like to additionally acknowledge support from the UMR University Transportation Center. The Principal Investigators on both campuses are also thankful to Doug Gremmel of Hughes Brothers and Richard Smith, SI Concrete Systems for their participation as well as the generous inkind material donation to this project. Support for the full-scale slab tests from UMC undergraduate honors students Kendall Tomes and Sarah Craig are also acknowledged. The authors would also like to thank the following individuals for numerous discussions during quarterly meetings for the project : Michele Atkinson, Tim Chojnacki Bryan Hartnagel, Paul Porter, and Shyam Gupta (all of MoDOT) and Peter Clogson (FHWA). Early discussions with Prof. Aftab Mufti of ISIS, Canada also helped develop ideas for the project described in this report. These contributions from Prof. Mufti are gratefully acknowledged. ii
EXECUTIVE SUMMARY New materials and design methods are being investigated for the design of bridge components to alleviate the current devastating corrosion problems. A research project was initiated at the University of Missouri (UM) and the Missouri Department of Transportation (MoDOT) to develop a nonferrous hybrid reinforcement system for concrete bridge decks by using continuous fiber-reinforced-polymer (FRP) rebars and discrete randomly distributed polypropylene fibers. This hybrid system may eliminate problems related to corrosion of steel reinforcement while providing requisite strength, stiffness, and desired ductility, which are shortcomings of FRP reinforcement system in reinforced concrete. The overall study plan includes: (1) development of design procedures for an FRP/FRC hybrid reinforced bridge deck, (2) laboratory studies of static and fatigue bond performances and ductility characteristics of the system, (3) accelerated durability tests of the system, and (4) static and fatigue tests on full-scale hybrid reinforced composite bridge decks. The test results showed that with the addition of fibers, structural performances of the system are improved. Although polypropylene fibers do not increase the ultimate bond strength, they provide enhanced ductile bond behavior. Also, with the addition of fibers, the flexural behaviors are improved with the increase of the ductility index µ by approximately 40%, as compared to the plain concrete beams. In addition, with the addition of polypropylene fibers, the durability of the system was improved. The large-scale slab tests revealed that crack widths were smaller for hybrid slab than for GFRP slab and were more readily comparable to that for steel reinforced slab, even while the global stiffness of the hybrid slab was more comparable to the GRFP slab. Design guidelines for steel-free bridge deck are proposed based on a similar design equations provided by ACI440. These equations were calibrated using the results of the above test program. Contrary to the current design methods, it is recommended that flexural design of deck slabs be carried out using working stress approach with mandatory checks on ultimate capacity and mode of failure. This approach is more practically relevant for hybrid reinforced FRP slabs. The large-scale tests proved that the proposed design guidelines for such hybrid system are adequate and are ready for implementation in the design a hybrid steel-free bridge deck. iii
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Page 3: FINAL REPORT RI02-002 Steel-Free Hy
Page 7 and 8: 3.4.1 Flexural-Sensitive Beam Speci
Page 9 and 10: LIST OF FIGURES Fig. 2.1 Direct pul
Page 11 and 12: Fig. 4.32 Fig. 4.33 Fig. 4.34 Fig.
Page 13 and 14: control as well as monitoring of th
Page 15 and 16: Table 8.1 Summary of Design Moments
Page 17 and 18: f GFRP allowable stress in the GFRP
Page 19 and 20: 1. INTRODUCTION 1.1. BACKGROUND AND
Page 21 and 22: continuous reinforcing bars, or com
Page 23 and 24: pitting of steel bars results from
Page 25 and 26: ehavior under different cover thick
Page 27 and 28: 2. BACKGROUND INFORMATION 2.1 BOND
Page 29 and 30: This test method has several disadv
Page 31 and 32: of the behavior of the FRP. A numbe
Page 33 and 34: applying tension to the reinforcing
Page 35 and 36: each of the two types of GFRP, alon
Page 37 and 38: second specimen was tested to 1,000
Page 39 and 40: of failure, bond strength can be ma
Page 41 and 42: The bar that had been exposed for 8
Page 43 and 44: modeled one-dimensionally. At the o
Page 45 and 46: The one bar-scale model presented b
Page 47 and 48: esistance to crack growth in the ha
Page 49 and 50: place forms made of concrete precas
Page 51 and 52: perpendicular to the main reinforce
Page 53 and 54: X = the distance in feet from load
Page 55 and 56:
where A=effective tension area, in
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E=the effective length of slab resi
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d c = Dist. From extreme tension fi
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The unfactored wheel loads placed o
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The cover of the bottom of the cast
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AASHTO AASHTO LFD LRFD MODOT NOTES
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2.4 DUCTILITY REALTED ISSUES FOR FR
Page 69 and 70:
Based on experimental data, Vijay a
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Figure 3.1 GFRP Tensile specimen wi
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Two test configurations were used f
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correlation has been observed betwe
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3.3.1.2 Test Specimens Test specime
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This kind of specimen is not repres
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Figure 3.7 Casting operations for t
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Figure 3.9 Close-up photograph of m
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flexural beams were tested at UMC.
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Table 3.5 Flexural ductility test s
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Table 3.6 Experimental program for
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Data were recorded using a customiz
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thick and 1.5 in. wide stainless st
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The third slab used a hybrid reinfo
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Table 3.9 Reinforcement and spacing
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4. STATIC AND FATIGUE BOND TEST RES
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condition not exhibiting in real st
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u√f`c(MPa/√MPa) 3.2 2.8 2.4 2 1
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the loss of chemical bond, the curv
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of the embedded area had large bond
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Slip (in.) 0 0.2 0.4 0.6 0.8 1 1.2
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negligible mechanical bearing. Only
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were not in full contact because of
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specimens without fatigue loading,
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110.00% 100.00% 90.00% 80.00% 70.00
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approximated by f ct = 6. 8( f c '
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42 was obtained. As mentioned previ
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FRC Plain d) Crack patterns in #4 G
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4FC3 Pullout N/A 4FG1 Splitting 0.0
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I.D. Ultimate Bond Strength u (psi)
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4.3.2 Theoretical Prediction of Bon
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e be be le C (a) Schematic pullout
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By assuming the concrete strength o
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esponse until failure is initiated.
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the bond specimens with respect to
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typical load - end slip response fo
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18 Deflection (mm) 0 1 2 3 4 5 6 7
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14 12 Deflection (mm) 0 2 4 6 8 10
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4.4.2.3 Stiffness Degradation Speci
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110 Number of Cycles 0 20,000 40,00
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10 9 Deflection (mm) 0 1 2 3 4 5 6
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• Different bond mechanisms were
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index could be increased by as much
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0.4M u 0.8M u (a) VF4G (FRC beams)
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Table 5.1. Cracking moment and aver
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due to inadequate bond between the
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Moment (kN.m) 50 45 40 35 30 25 20
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As shown in Figures 5.5 through 5.7
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Specimen I.D. (1) Table 5.4. Compar
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m kN. ( n e Mom Deflection (in.) 0
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Based on the information provided b
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55 50 VP4C VP4C 450 45 400 40 VF4C
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Figure 5.18. Typical failure mode P
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Value used in this study Figure 5.1
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In the following sections, ductilit
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55 Curvature (1/in.) 0 0.0005 0.001
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6. ACCELERATED DURABILITY TEST RESU
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system, temperatures were varied fr
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observation was made by Tannous and
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6.3.1.2 Effect of environmental con
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3 Slip (in.) 0 0.1 0.2 0.3 0.4 0.5
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1.4 1.2 Slip (in.) 0 0.1 0.2 0.3 0.
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Slip (in.) 0 0.05 0.1 0.15 0.2 0.25
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After specimens had been subjected
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% Reduction of Design Bond Strength
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freezing-and-thawing cycles, damage
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Coated with Epoxy Solution Ingress
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ebar chairs were placed. This is ex
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concrete beams and from 4% to 8% fo
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55 50 Deflection (in.) 0 0.2 0.4 0.
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Table 6.3 Beam durability results f
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55 50 DP8G VP8G 450 45 40 DP8G 400
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Figure 6.31 Comparison of Ultimate
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I.D. Table 6.7. Ductility index usi
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55 50 Curvature (1/in.) 0 0.0002 0.
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• With the addition of polypropyl
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shows the electronic test control f
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North Box Girder Support LVDT 1 Pot
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Figure 7.6 Stress contours on the u
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as these, it is not possible to eli
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potentiometers). The inset shows lo
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loops observed near zero load is ty
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GFRP/CFRP reinforced slab does as w
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More than a characteristic of the c
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Figures 7.18 and 7.19 show schemati
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profile of lower reinforcement mat)
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while a check of ultimate capacity
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Load Modifier The structure is duct
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(a) Truck Loads (multiple presence
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(d GFRP − c) ε GFRP = ε c , and
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the transverse CFRP reinforcement o
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0.003 0.85 f’ c c a=β 1 c C ε C
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unrealistic based on results of ser
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parameters are identical to the one
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spacing of at least 10 in. in the t
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values. The bond specimens with a p
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• CFRP reinforced specimens exhib
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GFRP bars can be used exclusively f
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ASTM C 1543-02, “Standard Test Me
Page 267 and 268:
CAN/CSA-S6-00, 2000, “Canadian Hi
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Deflection,” Technical Report, De
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Mashima, M., and Iwamoto, K., 1993,
Page 273 and 274:
Status of the Nation's Highways, Br
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Table AI-3: Results From Compressio
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Steel Free Hybrid Reinforcement System for Concrete Bridge Decks ...

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