Stiffness of unreinforced masonry shear walls based on full-scale testing

Masonry shear walls are widely used in residential buildings to transfer horizontal loads to the foundations. Under such loading, early cracking occurs, followed by a rapid degradation of structural stiffness. While numerous studies address masonry behaviour under seismic actions, experimental investigations of masonry buildings subjected to monotonic horizontal loading remain scarce. This study investigates the stiffness and its degradation of unreinforced masonry shear walls using full-scale building models. The influence of wall openings, initial compressive stress, wall aspect ratio, and flange effects was examined. The experimental results demonstrate pronounced stiffness degradation after cracking. In both tested buildings, the elastic response accounted for approximately 77% of the maximum horizontal force. Crack initiation occurred at relatively low load levels. It was observed earlier in walls with openings: the first crack appeared in the shear wall containing a door opening, followed by the wall with a window opening. The total stiffness method proved effective for estimating the building's initial stiffness and the stiffness of individual stiffening walls. The proposed analytical approach also enabled a rational assessment of internal force distribution among walls with differing stiffness.