Numerical investigation of the fire resistance of protected cross-laminated timber floor panels

Several experimental investigations have been performed on timber elements to determine their fire resistance. However, the numerical modelling is nowadays an effective and inexpensive alternative method to investigate the behaviour of timber structures in fire conditions. Once validated on experimental data, finite element models can be used to understand more in detail the experimental behaviour, and then employed to carry out parametric studies where geometrical, mechanical and thermal properties are varied. After an extensive discussion on the state-of-the-art in numerical modelling of timber members and connections in fire conditions, the paper presents a two-dimensional model implemented in ABAQUS software package to simulate fire tests of cross-laminated timber (XLAM) floor panels protected with different cladding systems. The temperature distribution within the XLAM cross-section and the fire resistance of panels loaded out-of-plane were predicted through thermal and thermo-mechanical analyses, respectively. Since the stiffness and strength degradation of wood with temperature is still subject of research, a parametric study with different degradation laws was carried out. Numerical predictions were compared with experimental results showing acceptable accuracy, particularly when the degradation laws of the EN 1995-1-2 were used. The comparisons also show the need to model correctly the failure of the protective cladding for an accurate prediction of the thermal behaviour.