Influence of the type of support on the thermomechanical performance of beams in fire situations

This study examined the impact of the type of support on the thermomechanical performance of steel and timber beams in fire scenarios. Thermal and thermomechanical analyses were conducted on maçaranduba (Manilkara spp.) timber beams with a rectangular cross-section and A572 Gr. 50 steel beams with a W200x46.1 cross-section, 5 m in length, using the finite element method (FEM). The thermomechanical approach considered the interaction between the thermal and mechanical fields. Steel, being ductile and isotropic, had its failure represented by the von Mises theory. Wood, on the other hand, being anisotropic, was modeled orthotropically, exhibiting different behavior in traction and compression, perpendicular or parallel to the fibers. The results of the thermal analysis indicated a carbonization rate of 0.39 mm/min in the timber beams, which resulted in a reduction in the resistant cross-section and a nearly uniform temperature distribution in the cross-section of the steel beams during the course of the fire. With regard to the thermomechanical analysis, it was found that for steel, it is more advantageous to adopt support configurations that allow for axial displacement (AC1) to improve structural resilience by accommodating thermal expansion and preventing collapses. However, the support configurations had no significant influence on the performance of the timber beams, but it is crucial to incorporate measures that reduce the rate of carbonization. These findings highlight crucial aspects in the comprehension of the behavior of these materials and the bonding conditions of beams in fire situations.