| This study focuses on the out-of-plane behavior of unreinforced masonry bearing walls in buildings subjected to earthquake motions. Results from a set of shake table tests reveal that, in general, the walls performed very well despite the intensity of the base motion and the slenderness of the wall. This was due to the formation of a hinge at the base of each wall; the hinge allowed each wall to remain stable while rocking and supporting substantial gravity loads. Experimental results are compared with those simulated using nonlinear single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) computational models. The validated models are useful for establishing, through a parametric study, that permissible limits on wall slenderness as prescribed by current seismic guidelines (FEMA 356) are conservative and can be increased. A two-degree-of-freedom (2DOF) model is introduced as a simple tool for dynamic stability analysis of unreinforced masonry walls subjected to distortions at their top from an attached flexible floor diaphragm. The 2DOF model incorporates the nonlinear static (pushover) response of two cracked wall segments rocking as rigid bodies. |
