Seismic performance parameters of fully grouted reinforced masonry squat shear walls

Abstract

The displacement ductility, ductility-related seismic force modification factor, and the effective elastic stiffness are important force-based seismic design (FBD) parameters for reinforced masonry (RM) shear walls. In addition, stiffness degradation and equivalent viscous damping, are crucial displacement-based seismic design (DBD) parameters. This study analyzes previously reported test results of eight RM shear-dominated fully-grouted rectangular squat walls subjected to cyclic lateral excitations to evaluate the FBD and DBD parameters. The main variables of the tested walls are the level of axial compressive stress, vertical and horizontal reinforcement ratio, anchorage end detail, and the spacing of horizontal and vertical reinforcement. However, all tested walls had the same shear span to depth ratio equal to 1.25. The evaluated FBD parameters are compared to the Canadian, European and American standards. Moreover, based on the analysis, equations for the stiffness degradation of RM shear walls relative to their top drift limit or displacement ductility, are developed and presented for the examined walls. The ductility-related seismic force modification factor is computed on average 2.6, and 3.9, based on equal energy and equal displacement idealization, respectively. The US, and European standards ignore the axial stress effect on wall’s elastic effective stiffness and highly overestimate its value for the tested walls. This study presents, based on the tested walls, a guide design values for squat shear-dominated walls category that can be used in FBD and DBD.