Seismic Fragility Evaluation of Lightly Reinforced Concrete-Block Shear Walls for Probabilistic Risk Assessment

With the North American seismic codes moving toward adopting performance-based seismic design (PBSD) approaches, there is a need to develop seismic probabilistic risk assessment (PRA) tools for different construction systems, including reinforced masonry (RM). The current study focuses on the development of analytical fragility curves based on the performance of RM walls tested under base excitation generated by a shake table. The study has two phases. In the first phase, the seismic response of the RM shear walls is modeled using a simplified analytical model that was calibrated using previously reported shake table experimental results. The second phase of the study focuses on the development of fragility curves, as an essential component of a PRA framework, for two-story lightly reinforced masonry walls. In this phase, relevant limit states are defined and the corresponding capacities of the walls are quantified based on the shake table test results. The wall seismic demand levels are then determined through a probabilistic seismic demand analysis (PSDA) approach by performing 120 nonlinear response history analyses using the analytical model developed in the first phase. Fragility curves are derived based on the experimental capacity data and the analytical PSDA results. The results indicate that the lightly reinforced masonry shear wall category considered in this study would experience acceptable seismic performance associated with moderate lateral wall top-roof drifts even when subjected to ground motion records representing some of the highest seismic regions in eastern and western Canada. The study is a part of a larger ongoing PRA research program to provide the needed seismic performance data to facilitate the inclusion of different RM construction categories within the next generation of PBSD codes in North America.