الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Most of reinforced concrete (RC) structures built prior 1970s were designed and constructed with reinforcement details did not meet the current seismic design codes especially in terms of transverse reinforcement and anchorage length of beam bars. A simple and practical retrofit method is proposed for retrofitting deficient (non-seismically detailed) exterior beamcolumn joints based on fixing steel plates to the joint with different configurations. Six halfscale exterior RC beam-column joints were tested under a quasi-static cyclic loading with a constant axial load subjected to the column. The study included two control specimens representing code-detailed and deficient joints and four retrofitted specimens with different retrofitting schemes. The proposed approaches were designed to compensate the lack of joint transverse reinforcement using different steel arrangement (X-shape, horizontal plates) and poor anchorage length of beam bars using plates tied by external or internal anchors. One of the retrofit methods is applicable in the presence of transverse beam. The test results indicated that the deficient joint exhibited brittle joint shear failure unlike the code-detailed joint which failed by flexural yielding in the beam. The proposed retrofitting methods effectively prevented the brittle joint shear failure and increased the joint strength, ductility, stiffness, and energy dissipation. A softened strut and tie model was applied on the control specimens and modified to consider the different retrofit schemes to calculate joint shear strength of all specimens. The predicted shear capacities of the joints using the modified strut and tie model are close to the experimental with a coefficient of variation of 0.11 which indicates that the modified model could be used to predict the shear strength of the retrofitted specimens. A nonlinear finite element analysis for modeling the cyclic behavior of beam-column joints using SeismoStruct software was presented in this study. The proposed joint model considered the effect of anchorage of beam longitudinal reinforcement embedded in the joint, the inelastic shear response of the reinforced concrete joint core, and joint shear interface. The model was modified to consider the different shapes of steel plates used in the retrofitted specimens. The proposed numerical model was able to predict the hysteretic behavior of the tested specimens, especially in simulating the effect of pinching, stiffness deterioration, and strength degradation due to the cycle loading.