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

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experience with several steel-free bridge deck and other similar structures as described in Chapter 2. The approach proposed in this study where the deck slab is reinforced with a nonferrous hybrid reinforcement system comprising continuous FRP bars and short discrete randomly oriented fibers is somewhat different from the Canadian concept. Nevertheless, it is beneficial to study and understand the Canadian experience in steel-free bridge deck designs. The innovative Canadian approach is also reported on. The above reviews facilitated design emphasis on parameters that will be useful in the current effort to develop design procedures for a non-ferrous hybrid reinforced concrete bridge decks. 1.4.2. Bond Performance of FRP Reinforcement in an FRC Matrix Good bond performance is essential to ensure effective use of bar strength and avoid undesired brittle failures. While deformed steel bars develop mechanical bond resistance by means of steel lugs on concrete, FRP bar develop bond resistance either by mechanical resistance (helical patterns mimicking deformed steel bars) or by frictional resistance between concrete and the uneven bar surface. Types of FRP bar, their shape and their surface treatment dictate their bond performance. Several studies have addressed this issue in recent years. Unique to this proposed work is combining FRC, made of short polypropylene fibers as discrete reinforcement, with FRP as primary continuous reinforcement. The short fibers tend to improve the mechanical properties of the concrete matrix by enhanced resistance to crack growth. Thus, by mitigating secondary cracking and reinforcing the weak zone around FRP bars, FRC improves the bond characteristics of the hybrid reinforcing system. Three test methods are commonly used to study bond behaviors: namely, pullout bond test, splitting bond test, and flexural bond test. These different test configurations provide different information with regard to bond behaviors. Pullout tests represent the concept of anchorage and are usually adopted to study the bond behavior between rebar and concrete. Although pullout test causes concrete to be in compression and the reinforcing bar to be in tension, a stress condition not exhibited in real structures, a reasonable correlation has been found between structural performance and measures of performance in the pullout test (Cairns and Abdullah, 1992). Splitting bond tests are often used to study the splitting bond 6
ehavior under different cover thicknesses. The effect of the transverse reinforcement on bond behavior can be avoided when properly designed. Splitting bond tests simulate the stress field of real structures to some extent - while it can simulate the shear stress field it does not represent the stress gradient induced by bending. Flexural bond tests have the advantage of representing actual stress fields in beams and the cover effects on bond. However, it requires considerable confining reinforcement to avoid a shear failure. All three test configurations were investigated and compared to provide a complete picture of interface interactions in FRP reinforced concrete. 1.4.3. Ductility Characteristics in FRP Reinforced FRC Systems Ductility is an important design requirement in many structures and minimum levels of ductility are mandated by design codes. In reinforced concrete structures, when using conventional materials (i.e. steel and concrete) ductility is provided by the proper combination of the two materials cross-sectional ratios allowing the ductile material (steel) to yield first. In FRP reinforced concrete members, both the FRP and concrete exhibit relatively brittle behavior. Traditional definitions of ductility used in conventional steel reinforced concrete structures are not appropriate for FRP reinforced concrete. However, in FRC, the short fibers tend to increase the toughness of concrete allowing for a significant increase in the total energy absorption of the system, which can be regarded as inducing ductility in concrete. More recently energy-based (Naaman and Jeong, 1995) and deformation-based (Jaeger et al., 1995) approaches have been developed and successfully used for reinforced concrete structural elements. These approaches will be reviewed for application in the context of the hybrid reinforcement system used in this investigation. In addition to being phenomenologically more appropriate for FRP reinforced systems, the presence of fibers in the concrete matrix and its contribution to enhanced toughness and crack growth resistance will make newer measures of ductility even more relevant. 7
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: pitting of steel bars results from
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
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
Page 79 and 80:
This kind of specimen is not repres
Page 81 and 82:
Figure 3.7 Casting operations for t
Page 83 and 84:
Figure 3.9 Close-up photograph of m
Page 85 and 86:
flexural beams were tested at UMC.
Page 87 and 88:
Table 3.5 Flexural ductility test s
Page 89 and 90:
Table 3.6 Experimental program for
Page 91 and 92:
Data were recorded using a customiz
Page 93 and 94:
thick and 1.5 in. wide stainless st
Page 95 and 96:
The third slab used a hybrid reinfo
Page 97 and 98:
Table 3.9 Reinforcement and spacing
Page 99 and 100:
4. STATIC AND FATIGUE BOND TEST RES
Page 101 and 102:
condition not exhibiting in real st
Page 103 and 104:
u√f`c(MPa/√MPa) 3.2 2.8 2.4 2 1
Page 105 and 106:
the loss of chemical bond, the curv
Page 107 and 108:
of the embedded area had large bond
Page 109 and 110:
Slip (in.) 0 0.2 0.4 0.6 0.8 1 1.2
Page 111 and 112:
negligible mechanical bearing. Only
Page 113 and 114:
were not in full contact because of
Page 115 and 116:
specimens without fatigue loading,
Page 117 and 118:
110.00% 100.00% 90.00% 80.00% 70.00
Page 119 and 120:
approximated by f ct = 6. 8( f c '
Page 121 and 122:
42 was obtained. As mentioned previ
Page 123 and 124:
FRC Plain d) Crack patterns in #4 G
Page 125 and 126:
4FC3 Pullout N/A 4FG1 Splitting 0.0
Page 127 and 128:
I.D. Ultimate Bond Strength u (psi)
Page 129 and 130:
4.3.2 Theoretical Prediction of Bon
Page 131 and 132:
e be be le C (a) Schematic pullout
Page 133 and 134:
By assuming the concrete strength o
Page 135 and 136:
esponse until failure is initiated.
Page 137 and 138:
the bond specimens with respect to
Page 139 and 140:
typical load - end slip response fo
Page 141 and 142:
18 Deflection (mm) 0 1 2 3 4 5 6 7
Page 143 and 144:
14 12 Deflection (mm) 0 2 4 6 8 10
Page 145 and 146:
4.4.2.3 Stiffness Degradation Speci
Page 147 and 148:
110 Number of Cycles 0 20,000 40,00
Page 149 and 150:
10 9 Deflection (mm) 0 1 2 3 4 5 6
Page 151 and 152:
• Different bond mechanisms were
Page 153 and 154:
index could be increased by as much
Page 155 and 156:
0.4M u 0.8M u (a) VF4G (FRC beams)
Page 157 and 158:
Table 5.1. Cracking moment and aver
Page 159 and 160:
due to inadequate bond between the
Page 161 and 162:
Moment (kN.m) 50 45 40 35 30 25 20
Page 163 and 164:
As shown in Figures 5.5 through 5.7
Page 165 and 166:
Specimen I.D. (1) Table 5.4. Compar
Page 167 and 168:
m kN. ( n e Mom Deflection (in.) 0
Page 169 and 170:
Based on the information provided b
Page 171 and 172:
55 50 VP4C VP4C 450 45 400 40 VF4C
Page 173 and 174:
Figure 5.18. Typical failure mode P
Page 175 and 176:
Value used in this study Figure 5.1
Page 177 and 178:
In the following sections, ductilit
Page 179 and 180:
55 Curvature (1/in.) 0 0.0005 0.001
Page 181 and 182:
6. ACCELERATED DURABILITY TEST RESU
Page 183 and 184:
system, temperatures were varied fr
Page 185 and 186:
observation was made by Tannous and
Page 187 and 188:
6.3.1.2 Effect of environmental con
Page 189 and 190:
3 Slip (in.) 0 0.1 0.2 0.3 0.4 0.5
Page 191 and 192:
1.4 1.2 Slip (in.) 0 0.1 0.2 0.3 0.
Page 193 and 194:
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
Page 199 and 200:
freezing-and-thawing cycles, damage
Page 201 and 202:
Coated with Epoxy Solution Ingress
Page 203 and 204:
ebar chairs were placed. This is ex
Page 205 and 206:
concrete beams and from 4% to 8% fo
Page 207 and 208:
55 50 Deflection (in.) 0 0.2 0.4 0.
Page 209 and 210:
Table 6.3 Beam durability results f
Page 211 and 212:
55 50 DP8G VP8G 450 45 40 DP8G 400
Page 213 and 214:
Figure 6.31 Comparison of Ultimate
Page 215 and 216:
I.D. Table 6.7. Ductility index usi
Page 217 and 218:
55 50 Curvature (1/in.) 0 0.0002 0.
Page 219 and 220:
• With the addition of polypropyl
Page 221 and 222:
shows the electronic test control f
Page 223 and 224:
North Box Girder Support LVDT 1 Pot
Page 225 and 226:
Figure 7.6 Stress contours on the u
Page 227 and 228:
as these, it is not possible to eli
Page 229 and 230:
potentiometers). The inset shows lo
Page 231 and 232:
loops observed near zero load is ty
Page 233 and 234:
GFRP/CFRP reinforced slab does as w
Page 235 and 236:
More than a characteristic of the c
Page 237 and 238:
Figures 7.18 and 7.19 show schemati
Page 239 and 240:
profile of lower reinforcement mat)
Page 241 and 242:
while a check of ultimate capacity
Page 243 and 244:
Load Modifier The structure is duct
Page 245 and 246:
(a) Truck Loads (multiple presence
Page 247 and 248:
(d GFRP − c) ε GFRP = ε c , and
Page 249 and 250:
the transverse CFRP reinforcement o
Page 251 and 252:
0.003 0.85 f’ c c a=β 1 c C ε C
Page 253 and 254:
unrealistic based on results of ser
Page 255 and 256:
parameters are identical to the one
Page 257 and 258:
spacing of at least 10 in. in the t
Page 259 and 260:
values. The bond specimens with a p
Page 261 and 262:
• CFRP reinforced specimens exhib
Page 263 and 264:
GFRP bars can be used exclusively f
Page 265 and 266:
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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