Numerical simulation of the fire behaviour of facade equipped with aluminium composite material‐based claddings‐Model validation at large scale

Abstract

Summary The recent fire events in buildings involving combustible cladding systems have raised concerns regarding the risk that these systems can pose. Understanding such facade fires is complex as they involve a combination of various products and system. Facade fire propagation tests at ISO 13785‐1 intermediate scale were performed on different combinations of aluminium composite material (ACM) claddings and insulants. Simulations were addressed to reproduce these tests and were validated in terms of thermal conditions in the system. This allowed additional investigation and understanding of fire propagation on the facade and more accurate determination of the fire behaviour of the overall system. In this paper, the scaling influence on the fire behaviour of ACM clad systems is investigated with simulations performed to reproduce fire tests at the BS8414‐1 larger scale on three different combinations of ACM and insulants. The contributions of the cladding and insulant were numerically investigated. The fire behaviour of each component and of the overall system is validated by comparison with experiments. Simulations and tests show that the ACM cladding is the most important element driving the global fire behaviour of the systems. In particular, ACM‐PE‐based cladding systems, whatever the insulant, show extensive fire propagation while its degradation affects the integrity of the cavity.

Reconstruction of the Grenfell Tower fire – Part 4: Contribution to the understanding of fire propagation and behaviour during horizontal fire spread

“…A comparison between observations from the real fire and the modelled [ACM‐PE + MW] fire propagation shows the same shape during the first and second linear phases from 01:08 am to 01:22 am After 01:24 am , the vertical fire spread was faster for the model with [ACM‐PE + MW] than for the [ACM‐PE + PIR] configuration. In References 6 and 7, the same slight differences in the fire behaviour of [ACM‐PE + PIR] and [ACM‐PE + MW] systems were observed at intermediate and large test scales, where the use of [MW] as the insulation tended to slightly increase the fire spread. This increase was related to the quicker start of combustion in the [MW] system and to the energy absorbed by the [PIR] for charring, thermal cracking and pyrolysis, leading to a competition between thermal and thermochemical effects.…”

“…This feature is used to take account of the destruction of the cladding as observed experimentally in the aforementioned medium‐ and large‐scale fire tests. Reference 7 addresses the justification of the numerical model used for thermal degradation analysis.…”

“…In previous studies, 6,7 a multi‐scale numerical approach was used to assess the fire performance of the refurbished façade system used on the Grenfell Tower. This was underpinned by intermediate scale ISO 13785‐1 8,9 and large‐scale BS8414‐1 7,10 reaction‐to‐fire tests and used the computational fluid dynamics (CFD) code fire dynamics simulator (FDS) version 6 11‐15 . The output of these simulations showed that the ACM cladding was the main product driving the overall fire behaviour of façade construction in this specific system.…”

“…The output of these simulations showed that the ACM cladding was the main product driving the overall fire behaviour of façade construction in this specific system. In particular, systems that featured ACM cladding made with a polyethylene core (ACM‐PE) showed extensive fire propagation regardless of the insulant used 7,16 …”

“…This work comprises the modelling of horizontal fire propagation for the whole Grenfell Tower considering both façade and apartments. The thermal and combustion characteristics used for the façade system were validated in References 6 and 7 at intermediate and large scales. The HRR for the initial fire and the contribution of the apartment fires were estimated in Reference 22 and used in this study for each floor of the Tower.…”