Lateral strength force of URM structures based on a constitutive model for interface element

This paper presents the numerical implementation of a new proposed interface model for modeling the behaviour of mortar joints in masonry walls. Its theoretical framework is fully based on the plasticity theory. The Von Mises criterion is used to simulate the behaviour of brick and stone units. The interface laws for contact elements are formulated to simulate the softening behaviour of mortar joints under tensile stress; a normal linear cap model is also used to limit compressive stress. The numerical predictions based on the proposed model for the behaviour of interface elements correlate very highly with the test data. A new explicit formula based on results of proposed interface model is also presented to estimate the strength of unreinforced masonry structures. The closed form solution predicts the ultimate lateral load of unreinforced masonry walls less error percentage than ATC and FEMA-307. Consequently, the proposed closed form solution can be used satisfactory to analyze unreinforced masonry structures.