Seismic Retrofit of Reinforced Concrete Shear Wall by Integrating Selective Weakening and Self Centering

Many reinforced concrete (RC) buildings built prior to implementation of seismic design provisions in the 1970s are non-ductile and are at risk of excessive damage or even collapse during a major earthquake. In this dissertation study, a low damage retrofit scheme for non-code performing RC shear walls was investigated. In the retrofit scheme, traditional monolithic RC shear walls were converted into rocking walls by introducing a cold joint at the wall foundation interface and by adding external post-tensioning. Two retrofitted rectangular RC shear walls were tested in laboratory to investigate the proposed retrofit scheme. The retrofitted shear walls showed minimized damage, improved self-centering but lower energy dissipation capacity in comparison to the benchmark shear wall. A novel scheme using Ultra-High-Performance Concrete (UHPC) was proposed and investigated using laboratory testing and finite element (FE) simulation to anchor external PT elements to existing foundation in the retrofitted shear walls. Four anchorage specimens, that were designed to anchor 2/5th of the maximum PT force expected in the retrofitted shear walls, were subjected to laboratory testing. 3D FE models were calibrated based on the measured response and were used to investigate the proposed anchorage scheme at full-scale. The current code provisions to limit residual drift and predict critical concrete strains in precast rocking shear walls were examined based on published results. The provisions on residual drift were found to be satisfactory for hybrid rocking walls. Two code-conforming rectangular hybrid rocking shear walls were tested in the laboratory to provide improve alternative for predicting plastic hinge length in rocking walls, which is critical in estimating critical concrete strain.Laboratory testing of precast rocking shear walls has been limited to rectangular cross section. This dissertation addresses the gap in literature by testing a T-shaped precast rocking shear wall. The test specimen was designed in accordance with current design guidelines, at one-third scale of a prototype wall and tested under multi-directional loading up to 1.50% drift. Test observations showed damage to be limited at the rocking corners. The measured residual drift was lower than 0.25% and the measured energy dissipation ratio exceeded the prescribed limit of 12.5%.