Effectiveness of rocking walls system in seismic retrofit of vertically irregular RC buildings

Tadeh Zirakian , Omid Parvizi , Mojtaba Gorji Azandariani , David Boyajian

Abstract

This study examines the seismic vulnerability of vertically irregular reinforced concrete (RC) frame buildings, focusing on the effectiveness of retrofitting techniques such as rocking walls (RWs) in mitigating soft story mechanisms. Utilizing a seven-story residential apartment as a prototype in a high-seismicity urban area, this research performs detailed nonlinear simulations to evaluate both regular and irregular structures, both before and after retrofitting. Pushover and nonlinear time history analyses were conducted using OpenSees software, with a suite of nine ground motion records to capture diverse seismic scenarios. The findings indicate that retrofitting with RWs significantly improves seismic performance: for instance, roof displacements at the Collapse Prevention (CP) level decreased by up to 23% in the irregular structure with retrofitting compared to its non-retrofitted counterpart. Additionally, interstory drift ratios were more uniform post-retrofit, with Drift Concentration Factor (DCF) values approaching 1.0 across all performance levels, reflecting reduced variability in seismic response. The global ductility of the retrofitted buildings improved, with displacement ductility ratios increasing by up to 29%. These results underscore the effectiveness of RWs in enhancing global ductility, mitigating soft story failures, and providing a more predictable deformation pattern during seismic events. The study thus provides valuable insights into the robustness and costeffectiveness of using rocking walls for retrofitting irregular RC buildings.

Key Words

irregular buildings; numerical simulation; rocking walls; seismic retrofit; soft story failure

Address

Tadeh Zirakian — Department of Civil Engineering and Construction Management, California State University, Northridge, U.S.A.
Omid Parvizi — Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Mojtaba Gorji Azandariani — Centre for Infrastructure Engineering, Western Sydney University, Penrith, NSW, Australia
David Boyajian — Department of Civil Engineering and Construction Management, California State University, Northridge, U.S.A.

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