The performance of unreinforced masonry walls subjected to low-velocity impacts: experiments

Impact tests on a total of 21 full-scale unreinforced free-standing brickwork and blockwork walls have been performed in the laboratory using novel drop hammer/rotating quadrant apparatus. The impact loading generated in the laboratory had similar basic characteristics to accidental vehicle impacts (i.e. similar peak impact force and duration). The main variables investigated were wall length, wall thickness, masonry unit type/strength, impact location and end conditions. A number of different failure modes were identified. Mortar bonded walls subjected to a mid-height, mid-length, out-of-plane impact loading were observed to resist the loading in two phases: initial elastic action until fracture occurred, followed by gross displacements, resisted by friction at the base and both out-of-plane and in-plane inertial forces. When weak masonry units were used front face vertical fracture lines either side of the impact location were observed; when stronger units were used front face diagonal fracture lines were observed. Walls impacted close to their ends were observed to be significantly less capable of resisting impact loadings.