Risk-based optimum design of a device to simultaneously protect building columns against accidental impact, fire and progressive slab collapse

Recent studies on risk-based cost–benefit analysis of progressive collapse mitigation have shown that protection and strengthening measures should be effective and of limited cost, such that these measures have a net effect in reducing total expected costs, under low probability hazards. This sparked the idea of a device which could simultaneously protect building columns against fire and vehicular impact, and which could absorb the energy of collapsing slabs. This manuscript presents the proof-of-concept for such a device. The immediate target application is flat slab parking garages: flat slab buildings are particularly vulnerable to column loss events, and parking garages are exposed to significant fire and vehicular impact threats. The proposed device consists of cellular structures, known for their energy absorption and thermal insulation properties. Moreover, recent studies have shown that hazard probabilities play a major role in the optimal risk-based design for progressive collapse mitigation. Hence, the fire and vehicular impact hazard probabilities are treated as independent parameters in the analysis. Results show how the optimal protective device design changes with respect to such hazard probabilities. Results show the potential and effectiveness of the proposed device, while revealing new facets of structural system behavior under collapse propagation.