Seismic design of concrete structures for damage control

Abstract

Recent earthquakes have demonstrated that code-conforming modern (i.e. post-1970s) reinforced concrete (RC) buildings can satisfy life safety performance objectives. However, the accumulated earthquake damage in these modern buildings raised concerns about their performance in future events, contributing to widespread demolition and long-term closure of damaged buildings. The economic and environmental impacts associated with the demolition and long-term closure of modern buildings led to societal demands for improved design procedures to limit damage and shorten recovery time after earthquakes. To address societal demands, this study proposes a damage-control-oriented seismic design approach that targets functional recovery by ensuring structural component demands do not exceed the damage-control limit state (DLS) under design-level events. Herein, DLS is defined as the post-earthquake state beyond which the strength and deformation capacity of a structural component is compromised, and its performance in a future event cannot be relied upon without safety-critical repair. This study proposes a methodology to determine component deformation limits for the design of structures for damage control. Using the developed methodology, we propose component rotation limits for RC beams, columns, and walls. The seismic performance and capability of buildings designed using the proposed design approach to satisfy recovery-based performance objectives is demonstrated through nonlinear response history and recovery analyses (using the ATC-138 methodology) of four archetype frame buildings, designed per New Zealand standards to different beam deformation limits. The analyses show that building codes can achieve functional recovery using the proposed component deformation limits without the need for sophisticated recovery analyses.