Masonry walls under combined in-plane and out-of-plane loadings

This paper addresses the performance of masonry walls under combined in-plane and out-of-plane lateral loading with and without vertical precompression (referred to as multidirectional loading) through a series of interaction curves. It is hypothesized that the in-plane and the out-of-plane responses of the walls are not mutually exclusive. To examine the hypothesis, an explicit finite-element model, validated both for the in-plane and out-of-plane actions independently, based on a layered shell element and macroscopic masonry properties has been used and the interaction curves developed. Effects of precompression and aspect ratio to the interaction response of the walls subject to multidirectional loading have been examined. It is shown that the in-plane capacity reduces marginally up to and rapidly beyond a critical out-of-plane load level; therefore, determining in-plane capacity without regard to out-of-plane loading could be unsafe. A simplified nondimensional expression is developed to define the interaction curves for ease of design. It is shown that when the wall is reinforced, there exists two (lower and upper) critical out-of-plane load levels; therefore, the simplified nondimensional expression developed for the unreinforced masonry walls requires modification for application to reinforced masonry walls under combined loading.