Thermomechanical Analysis of Steel-to-Timber Connections under Fire and the Material Density Effect

This work presents a thermomechanical numerical analysis of a steel-to-timber connection with dowels in tension when exposed to fire using ANSYS (R) software. Three different wood density materials were considered. The connection is built by a three-dimensional model with a thermomechanical boundary condition. A nominal temperature-time curve, ISO 834, was used to simulate the fire effect. Numerical simulation to determine the field of thermal and mechanical stresses was performed using a combined problem. A temperature field was imposed for a given time instant of fire exposure, calculated through a thermal analysis in a transient regime. This temperature profile was coupled to an incremental tensile load, allowing the determination of the maximum mechanical resistance of the connection. According to this methodology, the load-bearing capacity of the connections in each fire rating will be determined. In addition, the numerical results allow verification of the wood density influence on the mechanical resistance of the connection exposed to fire. In conclusion, the load-bearing capacity decreases with fire exposure and with lower material density. With the proposed methodology, the effect of the wood density on the heat transferred through the connection under fire can be verified, and a thermomechanical complex model is proposed to solve and analyze this type of problem, which is the great motivation in this work. The numerical methodology represents well the thermomechanical behavior of the connection under fire. This procedure can be used, considering other different parameters, to improve the design and allow the study of the connection behavior as an alternative to the experimental tests.