Influence of the horizontal-to-vertical compressive strength of hollow clay bricks on the in-plane drift capacity of unreinforced masonry walls

The seismic damage of masonry walls is reflected in cracks that tend to start at the head and bed joints and subsequently propagates through the masonry units. In this regard, the horizontal-to-vertical compressive strength ratio of bricks might have the ability to influence failure modes and consequently the drift capacity. The existing experimental databases provide comprehensive information on the properties of bricks, but it is still limited to establish a correlation between the compressive strength ratio of bricks and deformation capacity of URM walls. This research studies the impact of the horizontal-to-vertical compressive strength ratio of bricks on the drift capacity of URM walls constructed with clay bricks vertically perforated and standard cement mortar. A series of 5 quasi-static cycle tests were performed, covering 3 different unit types with similar vertical strength but different compressive strength ratios (0.08, 0.18 and 0.27) and under 2 different levels of compression load. The 5 specimens were built of the same size (1.5 m long, 2.0 m high and 0.25 m thick), and were subjected to double bending boundary conditions to observe a shear-controlled behaviour. The outcome of this work analyzes the similarities and differences between failure mechanisms, together with the implications on the drift capacity of the masonry walls. The results obtained might be useful to correlate the local damage with limit states of buildings under seismic actions.