Thermomechanical three-dimensional finite element simulation of prestressed glulam timber beams

This study presents the development of a three-dimensional finite element model for simulating the fire behavior of prestressed glued-laminated timber. The finite element model, based on experimental data and the recommendations of Eurocode 5, accounts for the temperature-dependent evolution of the wood’s physical and mechanical properties. It enables a realistic prediction of the residual load-bearing capacity and post-fire structural behavior of timber beams following fire exposure and cooling to ambient temperature and has been validated through simulations of full-scale fire tests reported in the literature. Despite advances in numerical modeling, the fire behavior of such structures has been subject to only limited numerical investigations, with most studies being experimental or analytical. In this context, the proposed model provides a robust numerical tool capable of accurately analyzing fire performance and identifying char formation zones. The calculated temperature profile at the fire-exposed surface closely matches experimental results, and the temperature trends at different beam depths show only minor deviations from measurements. Furthermore, the maximum deviation between the predicted and measured char layer thickness after 60 min of fire exposure is approximately 4.4%, demonstrating the model’s accuracy in reproducing thermomechanical transfers within wood under higher temperatures. These results confirm that the model can reliably predict both the temperature distribution and char formation in prestressed glued-laminated timber beams during fire exposure.