Time-history analysis for unreinforced masonry walls in two-way bending

Abstract

Unreinforced masonry (URM) walls have been traditionally perceived to possess very little displacement capacity with respect to out-of-plane loading. This view, which has arisen due to low tensile strength of URM and therefore small displacements at which such walls begin to crack, has led to the widespread misconception among engineers that such walls possess no ductility and perform poorly under earthquake loading. However, both theoretical and experimental research have in fact shown that URM walls have the capacity to undergo significant deformations before collapse occurs, due to the rigid block action and frictional resistance mechanisms present in such walls. In addition, walls supported at their vertical edges have been shown to possess good energy dissipation characteristics which is further beneficial to seismic resistance. This paper presents a time history analysis model developed for simulating the dynamic response of URM walls subjected to out-of-plane loading. The hysteresis model incorporated into the analysis is capable of representing the nonlinear load versus displacement behaviour of walls with a range of boundary conditions that include one-way and two-way walls. The various parameters in the model can be calculated as a function of the properties of the URM wall, including the dimensions, material properties, axial loading and boundary support conditions. Comparisons of the analytical model with experimental shaketable tests show promising results.