Fire resistance of unprotected cross-laminated timber floor panels: Parametric study and simplified design

The larger use of cross-laminated timber (XLAM) panels as structural elements has taken the attention of the practitioners and researchers on their design in fire conditions. Simplified analytical design methods for fire resistance of timber structures are provided by the current European standard namely the EN 1995-1-2, however no provisions for XLAM floor panel are provided. The paper presents the results of a parametric investigation carried out on unprotected XLAM floor panels with different build-ups (number of layers, layer thickness, panel depth) exposed to standard fire on the bottom side and subjected to different load levels. Both advanced numerical simulations and analytical simplified methods are used to derive applied load-fire resistance design curves. Conservative approximations are proposed for XLAM floor elements with three, five and seven layers that do not show falling off of charred layers during the standard fire exposure. The proposed plots together with some tabular values allow a direct and conservative estimation of the fire resistance depending upon the applied load and the panel build-up.