Lateral Force–Displacement Response of Unreinforced Masonry Walls with Flanges

Abstract

The experimental in-plane force-displacement response of unreinforced masonry (URM) walls with flanges (return walls) subjected to pseudo-static cyclic lateral loading is presented. Each wall failed in a diagonal tension mode followed by bed-joint sliding. The effect of wall flanges was an increase in the displacement capacity of the in-plane loaded wall, in comparison with an in-plane loaded wall without flanges. The measured shear strengths of the walls were compared with an analytical model for determining the limiting diagonal tension strength of the walls, with a high level of correlation. The initial stiffness of the shear walls before the effective yield was compared with the initial stiffness as determined using conventional principles of mechanics for homogeneous materials, and it was found that with some approximations the initial stiffness could be satisfactorily determined. Because the bed-joint sliding failure mechanism exhibited by the walls is a deformation-controlled action, there is further displacement capacity beyond the effective yield displacement, and it was found that the walls could sustain in-plane lateral forces to a drift of at least 0.7%. Recommendations are provided for a general force-displacement relationship, which is consistent with the experimental data and can be used for modeling URM walls and improving acceptance criteria, such as those specified in ASCE/SEI 41-06.