Abstract
Observations and numerical studies have allowed an understanding the fire development inside apartments and over the façade during the Grenfell Tower fire. During these analyses, the highlighted need was for a deeper investigation into the failure of windows during the fire. This detailed and complex model for window failure validates the thermal breakage criteria used in fire simulations of the whole Grenfell Tower fire. However, the present investigation is dedicated to a single pathway for the influx of fire and toxic smoke. Other pathways from the façade to the apartments, such as the melting of elements surrounding the window frame, are not addressed here. To analyse window behaviour during fire, Finite Element Method thermomechanical modelling is used. First, a heat transfer analysis is performed for windows subjected to the external flames from the identified façade fire scenario. The thermal loads evaluated from the fire are applied to the window structures to estimate their failure times. Two window casement configurations, closed and tilted-in, are investigated numerically. Then, a thermomechanical analysis of the window is addressed for each casement configuration. The modelled failure times are compared with those used in the general fire development model and from the observations. The good correlation that is observed, regardless of casement configuration, justifies the use of a simplified criterion for window failure in CFD fire models.
Highlights
The fire behaviour of windows installed in a building facade has an important influence on fire development during an enclosure fire
The present work only investigates frame failure due to the thermal loads induced by the facade fire, and cannot claim to take into account all the events that may have led to window failure
The fire development analysis performed in [34] with the Computational Fluid Dynamics (CFD) code Fire Dynamics Simulator (FDS) was dedicated to the fire development inside the initial apartment (Flat 16, 4th floor), and to the fire spread over the facade to the apartment above (Flat 26, 5th floor)
Summary
The fire behaviour of windows installed in a building facade has an important influence on fire development during an enclosure fire. The failure mechanism for the formation of a ventilation opening from a glazed element comprising a window frame with thermal break is investigated in reference [15]. Reference [34] investigated the development of the initial internal kitchen fire at Grenfell Tower, its propagation through and around the kitchen window opening, over the facade, and its re-entry into subsequent compartments. ANSYS Mechanical APDL software [37] is used to perform a thermomechanical analysis of a window frame, as used in the Grenfell Tower refurbishment, to evaluate the heating of the different materials comprising the frame. The aim of the current study is to perform a deeper investigation into the thermal and thermo-mechanical behaviour, during the disaster, of the window system installed on Grenfell Tower, along with an evaluation of the thermal criteria for window failure. The resultant detailed and complex model allows the evaluation of the relevance of the hypothesis used in previous numerical studies of the Grenfell fire [34, 37]
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