Effects of unreinforced masonry wall slenderness ratio on out-of-plane post-cracking dynamic stability

Paper 55A large number of time-history analyses were performed on several unreinforced masonry (URM) walls that had different slenderness ratios, and the viability of adopting wall slenderness ratio as a criterion for seismic assessment was investigated. Several combinations of three wall properties were assumed to cover most walls found in New Zealand URM buildings, and 30 representative time-history records were used to perform analyses. Walls were either two-leaf thick with no overburden load applied or three-leaf thick having an overburden load applied equal to the weight of a typical second-storey two-leaf URM wall. Wall behavioural data was obtained based on a previous laboratory based study, and each wall was subjected to ground motion scenarios with increasing peak ground acceleration (PGA). The ground motion record PGA that caused the wall to undergo a displacement limit equal to 60% of wall instability displacement was identified, and the sensitivity of the obtained PGA to wall slenderness ratio was studied for all the used records. It was shown that increasing wall slenderness ratio resulted in the wall being more vulnerable.H. Derakhshan, J. M. Ingham and M. C. Griffit