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

Unreinforced masonry (URM) walls have been traditio nally perceived to possess very little displacement capacity with respect to out-of-plane loading. Thi s view, which has arisen due to low tensile strengt h of URM and therefore small displacements at which such wal ls begin to crack, has led to the widespread miscon ception among engineers that such walls possess no ductilit y and perform poorly under earthquake loading. How ever, both theoretical and experimental research have in fact shown that URM walls have the capacity to unde rgo significant deformations before collapse occurs, du e to the rigid block action and frictional resistan ce mechanisms present in such walls. In addition, wal ls supported at their vertical edges have been show n t possess good energy dissipation characteristics whi ch is further beneficial to seismic resistance. Th is paper presents a time history analysis model developed fo r simulating the dynamic response of URM walls subj ected to out-of-plane loading. The hysteresis model inco rporated into the analysis is capable of representi ng the nonlinear load versus displacement behaviour of walls with a range of boundary conditions that include on -way and two-way walls. The various parameters in the m odel can be calculated as a function of the propert ies of the URM wall, including the dimensions, material proper ties, axial loading and boundary support conditions . Comparisons of the analytical model with experiment al shaketable tests show promising results.