Multivariable fragility curves for unreinforced masonry walls

This study investigates the effect of the variation of the properties of unreinforced brick masonry walls, such as aspect ratio, prism strength, and axial load ratio, on determining the post-earthquake damage states of the walls using fragility curves. A database comprising 245 damaged unreinforced masonry walls is collected that have been tested under the quasi-static cyclic loads up to more than three percent drift ratios. The collected walls are categorized into four damage states according to the resisting lateral force during the cyclic loading obtained from the backbone of the hysteresis curves. Then, multivariable fragility surfaces based on the drift ratio and design properties of the walls are developed to determine the probability of reaching different damage states. The generated fragility surfaces show that aspect ratio and prism strength significantly affect the extent of damage to the URM walls, especially in higher damage states. The proposed fragility curves pave the path for a more reliable risk assessment of damaged unreinforced masonry walls and enhance the conventional fragility curves of guidelines such as HAZUS, which only depends on the variation of the drift ratio.