njit-etd2003-032 - New Jersey Institute of Technology

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13 A lot of studies have been conducted to explain the behavior of externally bonded FRP laminates used to increase the moment capacity of flexural members. However, not many studies have specifically addressed the shear strengthening. Berset (1992) at the Massachusetts Institute of Technology did the first research on FRP shear strengthening. He tested several RC beams with and without shear reinforcement in the form of GFRP (Glass Fiber Reinforced Polymer) laminates vertically bonded to both sides of the beam in the shear-critical zone. A simple analytical model for the contributions of the external reinforcement in shear was developed. In Berset's model, the FRP shear reinforcement was treated in analogy with steel stirrups. Failure occurs when the FRP laminate reaches the maximum allowable strain, which is determined by experiments. The second study reported in literature is that of Uji (1992), who tested reinforced concrete beams strengthened in shear with both CFRP fabrics wrapped around the beam and CFRP laminates bonded on vertical sides of the beam (with fibers either vertical or inclined). His model for CFRP's contribution to shear capacity is based on the bonding interfaces between the CFRP laminates and the concrete surface. The average shear stresses during the peeling-off of the fabrics are adopted, which is determined by experiments (about 1.3 MPa). The upper limit to the FRP contribution is given by its tensile strength. Dolan et al. (1992) tested prestressed concrete beams with externally applied AFRP (Aramid Fiber Reinforced Polymer) and concluded that such reinforcement did quite well for shear strengthening. Al-Sulaimani et al. (1994) did research on shear strengthening using GFRP (Graphite Fiber Reinforced polymer) laminates in the form of plates. Their model is
14 based on the assumption that the average shear stresses between the GFRP and the concrete are equal to O.8 MPa and 1.2 MPa for plates and strips, respectively. Ohuchi et al. (1994) carried out an extensive series of tests on RC beams strengthened in shear with CFRP wrap. They modeled the CFRP shear contribution in an analogy with steel stirrups, assuming a limiting strain for the external reinforcement equal to either tensile failure strain of CFRP or 2i3 of it, depending on the thickness of the fabrics. At another research effort, Chajes et al. (1995) did some experiments on RC beams strengthened in shear with different types of FRPs, namely glass, aramid, and carbon. Again, in their work, the shear contribution of FRPs is modeled in analogy with steel stirrups, and a limiting FRP strain is assumed to be equal to O.OO5 approximately, according to the experiments. Malvar et al. (1995) also conducted some research on this topic and found out that CFRP strengthening in shear was a highly effective technique. They also stated that the contribution to shear capacity could be obtained by using the similar analysis for steel stirrups, and the limiting strain was equal to the tensile failure of the CFRP. Vielhaber and Limberger (1995) reported that on the shear strengthening of large scale reinforced concrete beams with CFRP fabrics and demonstrated through testing that even small amounts of external reinforcement provided considerable safety against brittle shear failure. Sato et al. (1996) did some research on RC beams strengthened in shear with either CFRP strips or continuous laminates, and described that the observed failure mode
Page 1 and 2: Copyright Warning & Restrictions Th
Page 3 and 4: ABSTRACT SHEAR STRENGTHENING OF RC
Page 5 and 6: SHEAR STRENGTHENING OF RC BEAMS USI
Page 7 and 8: APPROVAL PAGE SHEAR STRENGTHENING O
Page 9 and 10: This dissertation is dedicated to m
Page 11 and 12: TABLE OF CONTENTS Chapter Page 1 IN
Page 13 and 14: TABLE OF CONTENTS (Continued) Chapt
Page 15 and 16: LIST OF TABLES Chapter Page 2.1 Max
Page 17 and 18: LIST OF FIGURES (Continued) Chapter
Page 23 and 24: 2 Additionally, special equipment i
Page 25 and 26: 4 5. To study the shear span to dep
Page 27 and 28: 6 1.4.1 Shear Strength of RC Beams
Page 29 and 30: Where A, is the area of shear reinf
Page 31 and 32: 10 usually be the same throughout t
Page 33: 12 1.4.2.2 Shear Strength of Contin
Page 37 and 38: CHAPTER 2 EXPERIMENTAL PROGRAM ON S
Page 39 and 40: 18 needed, which was 4Omm wide and
Page 41: 20 used for bonding of the strips t
Page 45 and 46: 24 2.2 Instrumentation and Test Pro
Page 47 and 48: 26 b) Beam Z4-90 The next beam was
Page 49 and 50: 28 CFRP strip suddenly detached fro
Page 51 and 52: 30 Figure 2.17 Failure of Beam ZC6.
Page 53 and 54: 32 capacity. The load went straight
Page 55 and 56: 34 Figure 2.22 Failure of Beam Z6-9
Page 58 and 59: 37 c) Failure Mechanism Apparently,
Page 60 and 61: 39 observed by a prolonged portion
Page 63 and 64: 42 c) Failure Mechanism Since diffe
Page 65 and 66: 44 The equation to compute CARP she
Page 67 and 68: 46 3.2 Design Approach Based on Mod
Page 70: 49 Arom Aigure 3.2, it can be obser
Page 74 and 75: 53 Equation 3.12 from curve fitting
Page 76 and 77: 55 strength. The method based on bo
Page 78 and 79: 57 Chajes, M. J. et al. (1996) also
Page 80 and 81: 3) CFRP continuous fiber sheet in t
Page 82 and 83: Figure 3.11 CARP strip in the form
Page 84 and 85:
63 Thus, a relationship between the
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65 2 fc bi,d I f =wife • t f ' fi
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67 Arom Table 3.4, it can also be o
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69 equal to 3.75, the beam specimen
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71 laminates. The surfaces of the f
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Figure 4.3 Configuration of CARP st
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75 16 beams were tested in this res
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79 Figure 4.7 Typical test setup. 4
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81 intact. The CFRP strip delaminat
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83 4.5.1.4 Beam Z11-S45. The CFRP s
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85 4.5.2 Beam Group 2 4.5.2.1 Beam
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87 4.5.2.3 Beam Z22-S90. This beam
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89 (b) Right Side Figure 4.15 Failu
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91 of the delamination, which consi
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93 Figure 4.18 Failure of Beam Z31-
Page 116 and 117:
95 4.5.4 Beam Group 4 4.5.4.1 Beam
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97 4.5.4.3 Beam Z42-FD. This was th
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99 (a) Side View of the Beam at Fai
Page 122 and 123:
101 4.6 Test Results and Discussion
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103 failure along the inclined crac
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105
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107 4.6.3 Beam Group 3 A summary of
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109 4.6.3.3 Failure Mechanism. No i
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111 ;how deflections at ultimate lo
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113 All of the lines in Figure 4.28
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115 ratio; line Z-F90 means the var
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117 Unlike regular beams with large
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119 orientation of the CFRP strips
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121 As for shear design of deep bea
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123 provisions of ACI Code (ACI 318
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125 stress due to shear as well as
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Figure 5.3 Distribution of transver
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Figure 5.4 Estimation of effective
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131 Where A and Ah are the areas of
Page 154 and 155:
Since the principal tensile stress
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135 laminates can be obtained from
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Table 5.1 Experimental and Computed
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139 Where i denote each type of rei
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141 the strongest beam in the 4-foo
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143 Figure 6.1 Failure of Beam ZC4-
Page 166 and 167:
145 Figure 6.3 Failure of Beam Z22-
Page 168 and 169:
147 6.2.4 Analysis of Test Results
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149 improves the performance of the
Page 172 and 173:
Figure 6.7 Test result of beam Z22-
Page 174 and 175:
Figure 6.8 Test result of Beam Z3I-
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155 equal to 69 degrees in this cas
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157 decreases, while the shear cont
Page 180 and 181:
APPENDIX A LOAD DEFLECTION CURVES O
Page 182 and 183:
161 Figure A.3 Load deflection curv
Page 184 and 185:
163 Figure A.7 Load deflection curv
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Figure A.11 Load deflection curve o
Page 188 and 189:
167 Figure B.1 Load deflection curv
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
173 Figure B.13 Load deflection cur
Page 196 and 197:
APPENDIX C LOAD DEFLECTION CURVES O
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177 Figure C.3 Load deflection curv
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179 Czaderski, Christoph. "Shear St
Page 202:
181 4, No. 4, Nov. 2000, pp. 198-20
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