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Reinforced concrete jacketing is one of the most frequently used methods for strengthening of reinforced concrete (RC) columns. A large number of experimental studies have been carried out to investigate the effectiveness of repair and strengthening techniques and interface treatment on the response of concrete jacketed columns. However, the effects of potential damage in existing column and quality of core concrete on the response of jacketed RC columns have not been investigated. One of the main goals of this study is to examine how the material properties of the existing column affect the overall response of the jacketed RC columns. Two computer models were developed and nonlinear analyses were performed to determine the moment-curvature relationships and axial load-moment interaction diagrams of concrete jacketed RC cross sections. The effects of material strength and magnitude of axial loads were investigated. It is determined that the strength of core concrete has no effect on the response of concrete jacketed RC columns under lower axial loads while it increases the strength and reduces the ductility under higher axial load levels.

In this study, an experimental investigation is conducted to determine the behavior of RC shear walls found in old and existing buildings that do not comply with the design rules in modern earthquake standards. Scaled reinforced concrete shear wall specimens are built with smooth bars and low concrete quality. The dimensions of the shear wall specimens were selected with an aspect ratio bigger than two as 2500, 1050, and 150 mm for the height, length, and thickness, respectively. Four specimens are representative of nonconforming shear walls, and one wall used as a reference specimen which was designed in accordance with recent building codes using deformed bars. The behavior of the shear walls is determined experimentally by displacement-lateral load relationship under lateral cyclic loading. The study used measurable parameters to investigate the behavior of the test specimens in terms of lateral force capacity, rigidity, ductility, dissipated energy, and displacement components contribution to the total lateral response of the walls. The results showed a substantial loss of stiffness, ductility and energy dissipation capabilities for the tested nonconforming shear walls. Moreover, it is proven in this study that these specimens are governed by the bar slip phenomena which demonstrated more than 80% contribution to the total lateral displacement capacity. In contrast, the reference shear wall exhibited a notable flexural behavior and plastic hinge formation. Additionally, the shear walls built with smooth reinforcement bars lost about 44% of their theoretical potential flexural capacity due to the observed bar slip failure.

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External jacketing of columns with Carbon Fiber Reinforced Polymer (CFRP) sheets is one of the most commonly used techniques to strengthen the existing reinforced concrete (RC) columns subjected to earthquake loads. In this paper, a parametric study is performed to examine the effects of CFRP jacketing, axial load levels and concrete quality on the total response of the CFRP jacketed RC columns. The newly computer code was developed to determine moment-curvature relationships of CFRP jacketed RC columns. Moment curvature analysis is carried out using three column sections with a fixed reinforcement ratio and three different concrete qualities, and also three different thicknesses of the CFRP wraps. The performance of jacketed RC columns in terms of ductility, strength, stiffness and energy dissipation is investigated. The results of the parametric study showed that strengthening RC columns with CFRP wraps has a significant effect on the total response of jacketed columns due to the confinement of concrete. However, the degree of enhancement in total response is also related to axial load levels.