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Out-of-plane seismic performance of unreinforced clay brick masonry walls Meisl, Christopher Stephan

Abstract

Given sufficient anchorage to the diaphragms, out-of-plane walls in unreinforced masonry buildings have been shown to crack above mid-height and rock as two rigid bodies. This study investigates the sensitivity of the rocking response to the type of ground motion and the quality of the wall construction. A parametric study using a nonlinear-elastic single-degree-of-freedom model suggests that buildings located on firm ground sites are less likely to experience out-ofplane wall failures compared with buildings located on soft soil sites. Shake table tests were conducted on four full-scale multi-wythe walls with a height-to-thickness (h/t) ratio of 12, varying construction quality, and using three different ground motions. All walls experienced cracking at approximately peak ground acceleration (PGA) of the 2005 National Building Code of Canada (NBCC) level for Vancouver, but exhibited a stable rocking behaviour without collapse beyond a ground motion 1.5 times the 2005 NBCC level. Simple analytical methods were used to calculate the un-cracked wall stiffness, maximum force on an un-cracked wall, cracking strength, and the maximum total force acting on a cracked wall. These results compared well with those observed in the tests. Finally, a rigid body numerical model was developed using the commercially available software, Working Model. The results obtained using this model compared well to the full-scale tests, accurately predicting the maximum relative displacement at the crack location for the scaled ground motions used in the testing program.

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