njit-etd2003-032 - New Jersey Institute of Technology

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3 1.2 Objectives of Proposed Research In order to take full advantage of the potential ductility of the RC beam, it is desirable that the beam fails in flexure rather than in shear. Shear failure is catastrophic and occurs usually without advanced warning. Many existing RO members are found to be deficient in shear strength and need to be repaired. Deficiencies occur due to several reasons such as insufficient shear reinforcement or reduction in steel area due to corrosion, increased service load, and construction defects. Externally bonded reinforcement such as Carbon Fiber Reinforced Polymer (OFRP) provides an excellent solution in these situations. However, detailed investigation in shear strengthening using externally bonded OFRP has been limited, and to a certain degree, controversial. The analytical models proposed in the literature sometimes are contradictory. The design approach for such reinforcement is far from complete and straightforward. To further understand the behavior of shear strengthening of RO beams using externally bonded OFRP laminates as the shear reinforcement, the following objectives of this research have been established: 1. To increase the database of shear strengthening using externally bonded composites. 2. To investigate the shear behavior and modes of failure of RO beams with shear deficiencies after strengthening with CFRP laminates. 3. To study the effect of various CFRP types and shear reinforcement configurations on the shear behavior of the beam. 4. To study the bond mechanism between the OFRP laminates and the concrete surface.
4 5. To study the shear span to depth ratio (a Id) effect on shear strengthening of deep beams using CFRP laminates. 6. To propose design approaches based on experiments and analytical studies. 1.3 Originality of Proposed Research Having made the point that the rehabilitation of the infrastructure is an important matter for the United States, the proposed research is expected to generate both the scientific knowledge and the engineering method in the infrastructure field. With the developing analytical model, and the design recommendations for the CFRP strengthened reinforced concrete beams, the proposed research will develop new methods to predict the strength and deformation of the OFRP strengthened concrete structures. The proposed experiment test will help understand the behavior of OFRP strengthened beams and other structural members; it will also be used to verify the validity of the previous proposed theories. The proposed research will greatly increase the applicability of the strengthening methods with externally epoxy-bonded CFRP strips. It will also broaden the knowledge related to the reinforced concrete structures as well. The originality of the proposed research can be found in the following aspects: I. The behavior of RO beams of different lengths in shear strengthening by externally bonded OFRP laminates was investigated. In the proposed research, not only beams with different application methods were studied, but also beams with the same CFRP application but different lengths were investigated as well.
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: 2 Additionally, special equipment i
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 and 34: 12 1.4.2.2 Shear Strength of Contin
Page 35 and 36: 14 based on the assumption that the
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
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55 strength. The method based on bo
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57 Chajes, M. J. et al. (1996) also
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3) CFRP continuous fiber sheet in t
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Figure 3.11 CARP strip in the form
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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
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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-
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145 Figure 6.3 Failure of Beam Z22-
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147 6.2.4 Analysis of Test Results
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149 improves the performance of the
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Figure 6.7 Test result of beam Z22-
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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
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APPENDIX A LOAD DEFLECTION CURVES O
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161 Figure A.3 Load deflection curv
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163 Figure A.7 Load deflection curv
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Figure A.11 Load deflection curve o
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167 Figure B.1 Load deflection curv
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Page 192 and 193:
Page 194 and 195:
173 Figure B.13 Load deflection cur
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APPENDIX C LOAD DEFLECTION CURVES O
Page 198 and 199:
177 Figure C.3 Load deflection curv
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179 Czaderski, Christoph. "Shear St
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181 4, No. 4, Nov. 2000, pp. 198-20
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