Repairability-Based Design of Concrete Structures

Abstract Recent earthquakes demonstrated that modern reinforced concrete (RC) buildings (i.e., post-1970s) can satisfy the code-intended life safety performance objectives. However, the accumulated damage in these modern buildings raised concerns about their performance in any 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 repairability-based design approach for structural systems. The proposed approach aims to ensure that, under design-level earthquakes, damaged structural components have sufficient residual capacity to withstand future events without requiring safety-critical repair (the adopted definition of repairability); thereby ensuring the structural systems are safe for re-occupancy and can achieve functional recovery. Firstly, the repairability limit state for RC components is defined using an extensive database of past tests on RC components. Subsequently, component deformation limits are proposed for RC beams, columns, and walls. Furthermore, nonlinear response history and recovery (using the ATC-138 methodology) analyses of four archetype frame buildings, designed per New Zealand standards to different beam deformation limits, are used to assess the seismic performance and capability of the buildings to satisfy recovery-based performance objectives. By comparing the repairability fragility and functional recovery downtime estimates of the frame buildings for design-level events, it is concluded that it is feasible for the building code to target repairability in the design-basis earthquake in addition to collapse prevention in MCE.