الفهرس 
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Abstract
Design guidelines in international codes show noticeable differences with regards to shear strength prediction of concrete beams reinforced with Fiber reinforced Polymers, (FRP)., rectangular and flanged cross-sectional shape (R-section and T-section), and concrete compressive strength. Shear resistance of beams longitudinally reinforced with carbon FRP, (CFRP), bars is not well defined in the literature compared to beams reinforced with steel bars. This is mainly attributed to the low modulus of elasticity of CFRP compared to tradi-tional steel reinforcement resulting in relatively high strains generated in CFRP reinforcement and consequently wider cracks and lower contribution of the aggregate interlocking mecha-nism as well as dowel action in shear resistance.
In this thesis, experimental and numerical studies are conducted to investigate the shear behavior of concrete beams reinforced with CFRP. The experimental program comprises of testing seven simply supported beams with and without web reinforcement. The beams are T- shaped in cross-sections and reinforced with carbon fiber-reinforced polymer (CFRP) in both longitudinal and transverse directions under unsymmetric loading. The experimental program studies the effect of shear span-to-depth ratio a/d ranging from 1.0 to 3.5 of beams constructed with concrete having compressive strength fcu of 25 and 50 MPa, and longitudi-nal reinforcement ratio ρf % ranging from 0.56% to 1.49% on the shear failure mechanism. Increasing shear span-to-depth ratio a/d leads to decreases the load at shear failure of beams at D-regions (a/d<2.5), and increasing that at B-regions (a/d ≥2.5). At the D-regions the in-crease of concrete compressive strength from 25 to 50 MPa lead to increases of the load at shear failure by 21%. Furthermore, using CFRP stirrups with a spacing of 200mm lead to an increase of about 37% in compered to beams tested without stirrups. The numerical study in-vestigates the behavior of concrete beams reinforced in flexure with CFRP bars without transverse reinforcement to quantify concrete contribution in shear resistance. Specimens with R and T sections having different shear span-to-depth ratio, concrete compressive strength, and longitudinal CFRP reinforcement ratios are studied to determine the concrete contribution to shear resistance. The nonlinear program ATENA is used to simulate the actual behavior of concrete beams failing in shear and is verified against experimental results gath-ered from the literature to check the validity of the numerical model. The comparison shows good agreement between experimental and numerical results with a difference of 6% and then a parametric study is conducted to provide a better understanding of the effect of each parameter on the shear behavior of concrete beams reinforced with CFRP bars. The results of numerical models are compared to their counterparts predicted using different equations in codes and guidelines. It is found that the shear capacity of T-section is higher than R-section by about 15% to 25% mainly due to a change in cracking pattern due to the presence of the flange. Furthermore, the shear failure load increased by increasing the longitudinal reinforce-ment ratio as a result of decreasing strain and enhancement of dowel action. The effect of in-creasing concrete compressive strength was more pronounced on the shear capacity in arch action as opposed to diagonal tension regions. Finally, an equation is proposed to predict the shear capacity of concrete beams reinforced in flexure with CFRP bars. The shear capacity predicted by the proposed equation provided a good agreement with experimental results for 163 beams with a mean value of 1.01 and COV of 0.17.