Airbag testing of multi-leaf unreinforced masonry walls subjected to one-way bending

Six full-scale unreinforced masonry (URM) walls were built and tested to studythe post-cracking out-of-plane behavior of walls in the upper two or three stories of URM buildings. The one-way spanning two-leaf (230 mm nominal thickness) or three-leaf (350 mm nominal thickness) walls had variable heights from 2000 mm to 4100 mm and were subjected to one-way out-of-plane bending using a system of airbags. Initial testing was performed on each wall with zero overburden load applied, resulting in wall cracking and the development of post-cracking displacements of up to approximately 70% of the wall thickness. Four walls were re-tested in the cracked conditions but with overburden loads applied. It was found that analytical predictions underestimated the wall crack height by 16%, on average, and that the initial uncracked wall strength predictions were within 24% of the experimental measurements. It was also found that the maximum cracked wall resistance was, on average, 83% of the predicted value based upon the mechanics of rigid body rocking. An empirical relationship was proposed to account for the increase in the initial stiffness of the cracked walls due to the applied overburden.