ABSTRACT
ABSTRACT: Disproportionate (or progressive) collapse has become an increasingly important building structure performance issue following the collapses of the Alfred P. Murrah Federal Building in Oklahoma City in 1995 and the World Trade Center in 2001. Unified guidelines for providing progressive collapse resistance for new Federal building construction and major modernization projects in the United States recently have been issued (DoD 2009). These guidelines utilize, among other strategies, the alternative path method (APM) of analysis (Ellingwood & Dusenberry 2005), in which the robustness of a structure is assessed analytically by notionally removing major gravity load-bearing elements (columns, bearing walls), one at a time, and determining whether the damaged structure can sustain the local damage without further collapse. As currently implemented, however, these robustness assessment methods are entirely deterministic in nature, and do not take into account uncertainties in structural demands and resisting capacities subsequent to initiating damage (Stevens et al., 2008). Moreover, most recent research on the collapse resisting capacity of frames and their connections utilizes deterministic methods (e.g., Khandelwal & El-Tawil, 2007), although large variation of the capacities are known to exist. Little research has been conducted on the effects of these uncertainties on robustness assessment of structures.
