Flexural retrofit of existing reinforced concrete structural walls with various boundary element details under cyclic loading

A recent regulation in Korea allows the rehabilitation of aging apartment buildings, with vertical extensions up to three floors. To satisfy the increased flexural strength requirement, a method that places vertical reinforcements and re-casts concrete after crushing the boundary elements is proposed. In this study evaluates the flexural performance of shear walls to which the boundary element retrofit method was applied. Six real-scale specimens were fabricated and reversed cyclic loading tests were performed. The experiments showed that the flexural strength increased as the vertical rebar ratio of the boundary element increased. As the development length of the post-installed rebar was reduced, the anchorage of the rebar was effective. When using shear studs to connect the existing and the retrofitted wall, the flexural strength was similar; however, the deformation due to shear was controlled. It was confirmed that a discontinuous strain distribution occurred. Based on the experimental results, a flexural design model under limited conditions was proposed, which accurately predicted the flexural strength. However, because there is a tendency to overestimate the tensile rebar strain, future studies should develop a flexural design model that can make a more accurate prediction by further analyzing the variables affecting the boundary element retrofit method.