Evaluation of seismic residual capacity ratio for reinforced concrete structures

Abstract

Use of indices that quantify the seismic residual capacity of buildings damaged in earthquakes is one way to draw judgements on the building's safety and possibility of future use. In Japanese damage assessment guidelines, several approximate calculation methods exist to evaluate the residual capacity of buildings based on visually observed damage and simplifying assumptions on the nature of the building's response mechanism and member capacities. While these methods provide a useful residual capacity ratio that enables a ‘relative’ comparison between buildings, the exact relationship to a physically meaningful residual capacity is unclear. The aim of this study is to benchmark the ‘approximations’ of residual capacity. To do so, a shake-table test was conducted on a ¼ scale 4-storey RC structure and a residual capacity evaluation was undertaken based on observed damage states. With the help of a numerical model, a benchmark residual capacity at each of the damage states is determined and compared to the approximate residual capacity calculation results via guidelines. It was found that approximate methods are generally accurate prior to yield but can become overly conservative post-yield. Simplifying assumptions of equal member deformation capacity used in the residual capacity ratio calculation was found to be suitable given constraints of rapid field evaluations.