Comparison of behaviour of burnt beams models with effective and actual residual cross-sections in three point bending test

Abstract

Glued laminated timber beams exposed to fire of a variable duration were tested in three point bending. Three types of model geometries taking into account the effect of burning were created. Each model was examined for five material data sets. The maximum deflection obtained from FEM simulations was compared with the corresponding deflection w_el derived from a three point bending test of burnt beams. The analysis was performed with the help of Ansys^® software limiting attention to a liner elasticity with the maximum applied force F_el selected at the proportionality limit observed experimentally. Majority of FEM models provided smaller deflections compared to measurements except for the material set adopting Young’s moduli from the compression test. The best fit was observed for the material data set obtained from homogenization. No predominant preference among individual geometries was found promoting the computational model based on reduced cross-section as sufficiently accurate.