Experimental and numerical analysis of timber connections in tension perpendicular to grain in fire

• Tests on real-scale timber connections in normal conditions and under fire exposure.
• Steel-to-timber connections subjected to tension perpendicular to grain.
• Numerical FEM model is developed to simulate the behavior of tested connections.
• Numerical validation by comparisons with experimental results, in standard and fire exposure conditions.
• Numerical model used to analyze the thermo-mechanical behavior of connections.

Steel-to-timber connections, loaded in tension perpendicular to grain, are tested in cold and ISO-fire conditions. The experimental results are used to validate a 3D finite element model. This model is based on two different meshes for thermal and thermo-mechanical calculations. To manage the plastic yielding of materials, the mechanical model is based on von Mises criterion for steel and Hill criterion for timber. To take into account the brittle character of wood in transversal directions, Hill criterion is combined with Tsaï–Wu failure criterion. The thermal model, based on a continuous mesh, simulates the evolution of the temperature field inside the connections. The thermal and mechanical models are validated by comparison of their results with those from tests (temperatures, load–displacement curves). The developed thermo-mechanical model considers the mechanical properties evolution as a function of the temperature. The comparisons of calculated and experimental fire resistances show that the model predicts accurately the thermo-mechanical behavior of the connections. The validated model is used to observe mechanical parameters which are difficult to obtain experimentally, such as the load distribution among fasteners in fire conditions.