Progressive collapse: the case of composite steel-concrete frames

Vulnerability of structures to progressive collapse and mitigation of the effects of local damages are issues widely discussed inside the scientific community. Progressive collapses happened in recent years pointing out the need of new design criteria aiming to design robust structures, i.e. structures for which a local failure do not lead to disproportionate effects. Event control, specific local resistance, design of key elements, alternate path, compartmentalization and detailing rules are some of the preventive strategies proposed by recent studies and by design standards. This lecture briefly illustrates first the main facets of the problem; the approaches recommended by the standards are then reviewed. The key outcomes of some interesting studies are also presented, and their practical implications are underlined. Finally, the work carried on within European research projects to which the University of Trento has being contributing is discussed. In particular, the ongoing project comprises full scale tests of composite sub-frames aiming to provide an insight into the 3D action as a key factor in preventing progressive collapse by activating alternate paths of resistance