Collapse Fragility Evaluation of Ductile Reinforced Concrete Block Wall Systems for Seismic Risk Assessment

Seismic risk assessment is a critical first step toward mitigating the social and economic losses resulting from earthquakes. The FEMA P-58 document, prepared by the Applied Technology Council (ATC), provides a methodology for seismic performance assessment of buildings. The methodology consists of five main steps: assembling the building performance model, defining earthquake hazards, analyzing building response, developing collapse fragility, and quantifying performance. Owing to the probabilistic nature of the methodology framework, each step incorporates uncertainty. After the 2011 earthquake in Christchurch, New Zealand, a significant number of reinforced masonry low-rise buildings were deemed unusable, although the damage was repairable. This created a need to investigate the seismic collapse performance of a reinforced masonry shear wall (RMSW) system. In this study, the FEMA P-58 methodology is implemented to assess the performance of a typical RMSW office building designed according to the National Building Code of Canada (NBCC) 2010 and the Canadian Standards Association (CSA) S304-14 masonry design code provisions. In order to develop the building collapse fragility curves, an analytical model to predict the behavior of RMSW was developed. The model was calibrated using experimental results from an earlier study by the authors on scaled RMSW. Subsequently, an incremental dynamic analysis (IDA) procedure was performed to study the RMSW performance under a suite of ground motions consistent with the NBCC 2010 design spectrum for a high seismicity site in Victoria, British Columbia. The results of the IDA were used to develop collapse fragility curves for RMSW in order to facilitate the quantification of the collapse risk under different levels of seismic demand. This study is expected to catalyze the development of design provisions and subsequent adoption of RMSW in the next generations of seismic codes in North America.