Collapse Study of an Unreinforced Masonry Bearing Wall Building Subjected to Internal Blast Loading

A blast test was conducted inside a conventional, two-story, unreinforced, brick, bearing wall building scheduled to be demolished. A credible explosive device was placed inside the building on the ground floor and was detonated to investigate whether or not the building would collapse. The measured blast pressures, key material properties of the structure, and the structural configuration were used as input parameters to a single-degree-of-freedom software program, the single-degree-of-freedom blast effects design spreadsheet (SBEDS), commonly used in the United States to model unreinforced masonry walls subjected to blast loading. The net effect of overburden loads on the ground-floor bearing walls, including uplift by blast pressures on the ground-floor ceiling, was considered when investigating the validity of an appropriate resistance function (available in SBEDS) that defines out-of-plane bearing wall response. Comparisons were made between analytical and experimental permanent wall deflections and two alternatives, a simple displacement-based criterion and a resistance criterion, were used to estimate the building’s state relative to its estimated collapse limit state. It was found that SBEDS was able to model the experimental deflections quite well if effective input parameters were carefully considered. As a result, analytical and experimental determinations of the structure’s state were also in good agreement.