Numerical simulation of fire integrity resistance of full-scale gypsum-faced cross-laminated timber wall

Fire design requires three fire resistance criteria, namely integrity, insulation and load-bearing. In particular, repartition wall systems used in residential and commercial buildings are required to provide certification of insulation and integrity fire resistance and have to be analysed in the context of the characteristic time scales of a fire. This paper presents a numerical methodology to simulate the fire integrity resistance of full-scale timber-based wall systems exposed to fire. The main contribution of this paper, with regard to the existing literature, is the presence of cross-laminated timber (CLT) panel in the central part of the wall system, where the pyrolysis of timber was modelled explicitly in the energy balance equation system. For this end, a user-subroutine, called UMATHT, is developed and successfully implemented in the Abaqus finite element code for thermal analysis. The falling off of the gypsum boards under fire was considered implicitly in the FE model based on experimental observations. The obtained results show clearly the need to take into account explicitly the cracks and falling off of the gypsum boards for an appropriate prediction of the integrity fire resistance in order to reduce expensive experimental procedures.