Fire resistance of wooden dowelled cross-laminated timber panels under in-plane loading

This paper addresses the fire resistance of adhesive-free Cross-Laminated Timber (CLT) panels assembled with beech wooden dowels. A 180 mm thick, unprotected sample composed of six layers, each 30 mm thick, with overall dimensions of 3 m×3 m, was subjected to a standard fire curve for 100 min. The panel was loaded in-plane with a uniformly distributed load of 50 kN/m2. During the large-scale fire test, the temperature on the unexposed side and deformations at various points were monitored. Additionally, the final reduction in cross-section along the panel's height was assessed. The overall fire performance of the wooden dowel CLT (WDCLT) panels was satisfactory, with no failure after 100 min of exposure. A thermomechanical analysis of the panel was conducted to simulate the panel's mechanical behaviour under fire. Since no temperature data within the panel or direct measurements of the evolving charring depth were available, validation was performed against the deformation history. The charring rate time history was indirectly estimated from the model. A parametric analysis was conducted to simulate the load-carrying capacity ratio over time for the WDCLT panels, considering multiple layups with 5, 6, and 7 layers, with respective thicknesses of 150 mm, 180 mm, and 210 mm. The performance of these WDCLT panels was also compared to that of models representative of glued CLT panels, discussing the sensitivity of the fire resistance to the charred layer fall-off.