ABSTRACT
Multi-storey buildings should poses sufficient robustness to avoid local or global collapse in case of extreme events, like blasts, impacts, fire after earthquakes. Many of such structures, because of their destination, could be subjected to exceptional situations, for instance due to terrorist attacks. This was the case of the World Trade Center (WTC) towers that on September 11th, 2001 undertook a progressive collapse due to large aircraft impact. Available reports on this structural disaster indicate that the cause of the WTC collapse is related to several reasons: 1) the crash caused the failure of the bearing walls and the core column, which produced a simultaneous collapse of the floor structures; 2) truss beams suffered thermal expansion and deflected largely in a catenary state; 3) the bearing walls and the core columns were subjected to long heat exposure, which produced a lowering of strength and rigidity of the members which eventually led to the progressive collapse of the buildings (Byfield et al. 2007).
