Seismic Retrofit of Reinforced Concrete Shear Walls to Enable Reparability

Graduate Student: Sina Basereh

Principal Investigator: Pinar Okumus

Project Completion Date: July 2021

Laboratory tests were conducted at SEESL to investigate a new seismic retrofit method for reinforced concrete shear walls. The method involves weakening and self-centering by cutting the base of a wall, adding external post-tensioning, and providing additional confinement at wall toes. Three shear walls, one of which was a pre-retrofit benchmark specimen, were tested under quasi-static cyclic lateral loading using the strong floor-strong wall facility at SEESL. 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 related 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.

In addition to generating knowledge on the efficacy of the new seismic retrofit method, the results of testing were also used to validate numerical models that spanned from fiber element models to continuum models. The models were used for parametric studies and fragility analyses to understand the impact of parameters such as wall archetypes, post-tension amounts, continuous rebar amount, wall base cut shape, among others. The test results were also utilized to evaluate strength and drift capacity prediction methods for pre- and post-retrofit walls. The existing methods predicted the strength and drift capacity of the pre-retrofit specimen well. However, they were unconservative for strength predictions of post-retrofit specimens.

Basereh, S. 2021. Seismic retrofit of reinforced concrete shear walls using selective weakening and self-centering. Ph.D. Dissertation. State University of New York at Buffalo.

Basereh, S., and Okumus, P. 2021. "Test data on reinforced concrete shear walls retrofitted through weakening and self-centering." DesignSafe Data Depot. Accessed December 3, 2021. https://doi.org/1010.17603/ds2-4qx6-cm60

Basereh, S., Okumus, P., and Aaleti, S. 2020. "Reinforced concrete shear walls retrofitted using weakening and self-centering: numerical modeling." J. Struct. Eng., 146(7), 04020122. https://doi.org/10.1061/(ASCE)ST.1943-541X.0002669

Basereh, S., Okumus, P., and Aaleti, S. "Seismic retrofit of reinforced concrete shear walls to ensure reparability." In Proc., Structures Congress. 498-509. St. Louis, MO: American Society of Civil Engineers.

Basereh, S., Sharma, S., Baque, P., Blaggan, E., and Okumus, P. A. "Capacity and Damage Investigation of Precast Concrete Self-Centering Shear Walls." In Proc., 2021 Precast/Prestressed Concrete Institute and National Bridge Conference. New Orleans, LA: PCI.

This material is based upon work supported by the National Science Foundation (NSF) under Grant No. 1663063. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF.