Abstract
The progressive collapse of the World Trade Centre showed the devastating consequences of
pancake-type collapses, triggering significant research on failed floor impacts for different
forms of construction. In current high-rise construction, concrete flat slabs supported on
columns are widely used and, in this case, the fall of the slab could be prevented depending on
the detailing and the horizontal propagation of the collapse from one support to adjacent
supports. The activation and interaction of different phenomena during horizontal propagation
governed by the slab-column response is investigated in this study for cases of flat slabs with
and without integrity reinforcement. The paper focuses on slabs without punching
reinforcement which are more critical. A slab system analytical model is presented based on a
column removal scenario considering the dynamic response of the column-slab connections
before and after punching including membrane effects. The model was verified using finite
element models with solid elements at the connections. The results highlighted the key role of
integrity reinforcement towards preventing slabs from falling by means of activating tensile
membrane action concentrated around the columns.