Flexural deformations of URM piers: Comparison of analytical models with experiments

Despite the fact that displacement-based methods are now frequently applied when assessing the seismic performance of unreinforced masonry (URM) structures, the displacement capacity of in-plane loaded URM piers is still estimated from empirical rather than mechanical relationships. One idea for estimating a pier’s force-displacement curve including its displacement capacity that has been put forward in the past is based on the double integration of the curvature profile. The curvature is derived assuming a bilinear stress-strain relationship in the compression domain and neglecting the tensile strength of the masonry. We tested several identical URM piers under different constant axial load and shear span ratios while applying quasi-static horizontal cyclic in-plane loading. During testing, we tracked with a set of cameras the displacement of four LEDs on each full brick of the masonry piers. Therefore, we were able to determine the local deformations, e.g. average strains in the bricks and deformations of the joints. In this paper we will present experimentally determined local and global deformation quantities of one pier dominated by flexural deformations and compare these to the estimates from the analytical model. Differences between model and experiment will be discussed and first estimates of performance limits describing local deformations will be proposed.