In situ out-of-plane testing of unreinforced masonry cavity walls in as-built and improved conditions

Abstract Extensive research has been performed previously on assessing the out-of-plane (OOP) seismic performance of unreinforced fired clay brick masonry (URM) walls and the retrofitting of URM load-bearing and infill walls having a solid wall thickness. However, comparatively little research has been performed pertaining to URM walls with cavities (i.e., continuous air gaps separating wythes of brick from one another), despite the prominence of cavity masonry construction in various parts of the world. Hence, research was pursued with an emphasis on efficiently retrofitting URM cavity walls to enable the formation of semi-composite to composite behaviour when such walls were subjected to simulated seismic OOP loading. The research reported herein was based on an experimental testing approach wherein walls were loaded OOP using inflatable airbags. A total of ten tests were performed on nine separate URM cavity walls located in two separate buildings. The outcomes of the research program included determining the behaviour of URM cavity walls in one-way vertical flexure when bordered and when not bordered by rigid moment-resisting reinforced concrete frames; quantifying the improvement in drift levels of cavity walls prior to loss in strength and prior to collapse using a variety of cavity wall ties at different spacing; and establishing an equivalent solid wall thickness for cavity walls with various retrofit tie conditions for use in existing analytical models used to predict the OOP capacity of URM walls.