Testing and predicting the response of reinforced conrete shear walls retrofitted for recentering

Abstract

Laboratory tests were conducted to investigate the feasibility of a new retrofit method for reinforced concrete shear walls to enable self-centering and to evaluate strength and drift capacity prediction methods for pre- and post-retrofit walls. The proposed retrofit method involved cutting the base of a wall, adding external post-tensioning, and providing additional confinement at wall toes. Three shear walls, one benchmark and two retrofitted specimens, were tested under quasi-static cyclic lateral loading. The two retrofitted specimens differed in the initial post-tensioning force, external confinement plate size, and base cut shape. The benchmark specimen exhibited both flexure and shear damage, whereas the governing displacement mechanism for the retrofitted walls was rocking at the wall-to-foundation interface. As intended, the strengths of the retrofitted walls were 80% to 100% of that of the benchmark specimen. The retrofitted walls had larger drift capacities, fewer cracks, smaller areas of concrete crushing, lower residual drifts, and sufficient energy dissipation. The existing methods predicted the strength and drift capacity of the pre-retrofit specimen reasonably well, yet overestimated the strength and underestimated the drift capacity of the post-retrofit specimens.