A pyrolysis model for steel‐insulation sandwich building façade systems under fire

Sandwich panels consist of two thin‐walled steel faces plus an insulation core. For this core, materials are selected that provide high (shear) stiffness and high thermal resistance. When the panels are subject to fire, the (a) temperature‐dependent behaviour of the steel faces and (b) the possible chemical reactions of the insulation core should both be considered, to accurately predict the structural behaviour. Provisions in Eurocode EN 1993‐1‐2 can be used for (a). Regarding (b), this paper adds a verified pyrolysis model to Heat Transfer (HT) analyses, and obtained results are transferred to a Structural Response (SR) analysis. Then, the HT and SR analyses are demonstrated in so‐called One‐Way Coupled (OWC) and Two‐Way Coupled (TWC) fire‐structure simulations, the latter including the effects of structural failure on the fire behaviour. For the cases studied, structural behaviour for OWC and TWC simulations is very similar, which indicates that the structural (failure) behaviour does not significantly influence the fire behaviour. Differently, the difference in failure time between simulations with and without pyrolysis is more than 15%, due to endothermic effects. As such, for the cases studied, modelling of pyrolysis is more important than the effect of structural failures, and this modelling can be included as demonstrated in this paper.