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

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1.4.4. Accelerated Durability Tests on Hybrid Reinforced Systems Composite materials offer many advantages such as corrosion resistance, and their use in bridge decks have become more technically attractive and economically viable. However, long-term performances have to be clearly understood before it can be applied in the field with confidence. Much research has been completed on the durability issue regarding individual FRP components, but there is a paucity of literature on the durability of FRP and concrete system. The durability characteristics depends more on the interrelation between the materials than on the individual component’s property. In addition, the mechanical properties of a hybrid material system may deteriorate much faster than that suggested by the property degradation rates of the individual components making up the hybrid system (Schutte, 2004). The FRP/FRC hybrid system is relatively new and hence published literature on durability characteristics of this hybrid system is not currently available. Thus, accelerated durability tests on the FRP/FRC system are necessary. Specimens were subjected to cycles of freezethaw and high temperature while in contact with salt water. Bond characteristics and flexural performance were evaluated, and results were compared to those without environmental effects. 1.4.5. Static and Fatigue Tests on Hybrid Reinforced Slab Specimens Three full-scale tests on conventionally and hybrid reinforced slab systems designed using the procedures and data developed in this study were tested under static as well as fatigue loading conditions. Results from these tests allow understanding of the fatigue characteristics and potential failure modes in such hybrid reinforcing systems compared to the deck of conventional design. 8
2. BACKGROUND INFORMATION 2.1 BOND PERFORMANCE OF FRP IN A CONCRETE MATRIX One of the major parameters affecting the performance of reinforced concrete members is the bond characteristics of the reinforcement in concrete. Bond strength governs development length, crack width, crack spacing, and member deflection. Since bond is a governing design criterion, much effort has been expended researching the subject and developing constitutive models of the bond mechanism, for steel reinforcement and, more recently, for FRP reinforcement. Since its development around 1950, the deformed steel bar has become ubiquitous, and its bond characteristics have been determined fairly precisely by a vast number of experiments. Steel reinforcing bar has the advantage of uniformity: a grade 60 bar has stringently controlled yield strength, regardless of the manufacturer. Steel also exhibits isotropy, having equal strength in all directions. In bond failure between concrete and steel, it is the concrete that fails by crushing, leaving the steel undamaged. Fiber reinforced polymer, however, represents a wide range of materials and hence has a range of performance characteristics, which poses many design challenges. Composites have been under development since the 1960’s, but much of the technology is still new, and it is rapidly changing. The term FRP describes a wide range of fibers and polymers, including glass fiber reinforced, carbon fiber reinforced, aramid fiber reinforced, and others. Each of these types of FRP has very unique properties, which make the bond behavior unique. When considering GFRP bars only, the properties can still vary widely according to manufacturer. Also, the same bar can undergo different surface treatments to improve bond, leading to very different bond strengths. Unlike steel, FRPs demonstrate shear lag, producing lower values of ultimate tensile stress for larger cross-sectional areas, a characteristic that affects bond. As a result of these factors, the study of bond of FRP must still be carried out with regard to a particular type of bar. No broad generalizations on bond behavior can be made for such a varied collection of materials. The vast majority of the research that has been conducted on FRP reinforcement has focused on GFRP, which consists of what is commonly known as fiberglass. Compared to the other types of FRP, it is cheaper and much more widely available. In fact, most of the 9
Page 1 and 2: . . . . . . . . . . . . . . . . . .
Page 3 and 4: FINAL REPORT RI02-002 Steel-Free Hy
Page 5 and 6: EXECUTIVE SUMMARY New materials and
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: ehavior under different cover thick
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
Page 57 and 58: E=the effective length of slab resi
Page 59 and 60: d c = Dist. From extreme tension fi
Page 61 and 62: The unfactored wheel loads placed o
Page 63 and 64: The cover of the bottom of the cast
Page 65 and 66: AASHTO AASHTO LFD LRFD MODOT NOTES
Page 67 and 68: 2.4 DUCTILITY REALTED ISSUES FOR FR
Page 69 and 70: Based on experimental data, Vijay a
Page 71 and 72: Figure 3.1 GFRP Tensile specimen wi
Page 73 and 74: Two test configurations were used f
Page 75 and 76: correlation has been observed betwe
Page 77 and 78:
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
Page 91 and 92:
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
Page 187 and 188:
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
Page 195 and 196:
After specimens had been subjected
Page 197 and 198:
% 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
Page 215 and 216:
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
Page 249 and 250:
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
Page 269 and 270:
Deflection,” Technical Report, De
Page 271 and 272:
Mashima, M., and Iwamoto, K., 1993,
Page 273 and 274:
Status of the Nation's Highways, Br
Page 275:
Table AI-3: Results From Compressio
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Steel Free Hybrid Reinforcement System for Concrete Bridge Decks ...

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