Ventilated Façade Cladding Systems Subjected to Fire Load: Proposal of a Finite Element Calculation and Verification Methodology

The research addresses the topic of the mechanical behaviour of ventilated façades in case of fire. Whereas Italian and international regulations mainly focus on the reaction to fire of adopted materials, they don’t pay specific attention to the structural resistance of the façade. Most of the substructures adopted for ventilated façades are made of thin-walled steel or aluminium profiles, whose mechanical properties decay dramatically as the temperature increases. Furthermore, relevant thermal expansions modify the static design scheme leading to the onset of indirect actions and eventually to the structure’s failure. Due to the interconnection between the substructure and the cladding elements, the latter are also affected by these phenomena and susceptible to local damages. The falling of broken slabs could seriously compromise the safety of escaping building users and firefighters called to intervene. The article discusses the effect of fire on the structural resistance of ventilated façades, comparing the sensitivity to this phenomenon of profiles made of aluminium, carbon steel and stainless steel, with light and heavy cladding and different support systems. A finite element model was created to evaluate the temperature’s evolution over time and the consequent mechanical response for the various configurations. It is eventually demonstrated that not all current solutions can guarantee the stability of the façade.