Improving the seismic response of existing shear wall structures through experimentally validated high-performance RC retrofit

Since reinforced concrete (RC) multistory shear wall (MSSW) buildings comprise an essential part of modern urban built environments, it is vital to investigate the failure modes of existing SW systems through shake-table testing (STT) and propose effective techniques to mitigate their seismic risk. Thus, this study aims to enrich the literature with STT results of two-story shear wall (2SSW) specimens representing the lateral force-resisting system (LFRS) and construction practice of pre-seismic code MSSW structures before and after the retrofit. The study also experimentally verifies the effectiveness and modeling approach of a contemporary technique comprising thin high-performance reinforced concrete (HPRC) jackets and steel angles to enhance the SW buildings' seismic performance. Following assessing the seismic response of an existing SW specimen through pre-STT dynamic simulation, the first phase of the STT campaign confirmed the vulnerability of the substandard 2SSW primarily to bond slip failure at the construction joint. The STT results of a second 2SSW specimen retrofitted with HPRC jackets and steel plates confirmed that the unfavorable failure mode at construction joints was delayed from 0.96 g to 1.44 g. At the same input ground motion intensity that triggered the bond slip for the substandard 2SSW, the maximum top drift ratio and chord rotation of the enhanced 2SSW specimen were significantly reduced by 93.5% and 91 %, respectively. Finally, the effectiveness of the risk-mitigation technique when applied to a three-dimensional simulation model of a real-life SW building is confirmed through probabilistic seismic performance assessment. Under the most significant seismic events at the design-based earthquake (DBE), the probability of the continued occupancy damage state improved from 26 % to almost 100 %. Signs of damage, including impaired occupancy, structural damage, and collapse, were mitigated at DBE through the proposed measures to reduce the seismic risk of existing SW structures.