Thermal response of a curtain wall framing system under fire conditions

Abstract

Curtain walls are the most common façade system for modern office buildings. These facade systems play an important role in containing the fire to the floor of origin, and in the case of failure, the consequences can be severe. The heat from a fire could cause key elements to fail and sections of the facade to detach and fall from the building, facilitating flame spread to upper floors. However, no tools currently exist that can reliably predict the failure of such systems. This study computationally investigates the thermal response of two curtain wall framing systems to fire exposure – the stick system and the unitized system. The model predictions were validated against experimental data and the role of the screw connector is explored. A typical curtain wall aluminium frame system is modelled. The simulation results indicate that when heated from a compartment fire, thermal degradation of the aluminium frame is very rapid, occurring within the first 15 min of fire exposure for ISO-834 standard fire. When heated from the outside, considering the Eurocode external fire, thermal degradation of the pressure plate occurred within 10 min. With the addition of thermal protection or when using steel instead of aluminium profiles, thermal degradation was not predicted within the first 40 min of heating. The findings advance our understanding of curtain wall frame fire behaviour and can help develop more effective fire strategies and more resilient systems.