investigation of the geometric variation effect on seismic performance of low-rise unreinforced masonry structures through fragility analysis

Seismic risk assessment of unreinforced masonry (urm) buildings is an important process for seismic retrofit of essential facilities located in the central and southern united states (csus), as more than 30 % of facilities there are low-rise urm buildings. although hazus, the current loss estimation package for natural hazards, provides a set of fragility curves for such structures as an essential tool for conducting seismic risk assessment, seismic performance level variation due to geometric characteristics is not explicitly considered. this study investigates the effect of geometric variation of low-rise urm structures on seismic fragility assessment. utilizing urm building inventory information within the csus region, variables that describe the physical shape of urm structures are identified. a simplified composite spring model developed for urm structures is then utilized to monitor nonlinear seismic behavior. finally, seismic fragility curves corresponding to various shape configurations of urm structures are developed and compared. the analysis confirms that the length of out-of-plane walls and the number of stories in urm buildings have significant effects on seismic risk. an increase in the wall length or the number of stories makes urm buildings more vulnerable. on the other hand, the perforation ratio does not significantly affect seismic performance. it is suggested that using a single set of fragility curves is not adequate for seismic risk assessment of low-rise urm buildings unless geometric variation is considered explicitly. in addition, comparing the fragility curves developed in this study with hazus data, it is clear that the seismic vulnerability of low-rise urm is underestimated in hazus for lower limit states and overestimated for higher limit states.