Thermo-mechanical behaviour of timber-to-timber connections exposed to fire

A numerical model is developed to analyse the thermo-mechanical fire behaviour of timber-to-timber dowelled and bolted connections in tension parallel to wood grain. The experimental results of two series of tests are used to validate the model based on three-dimensional (3D) finite element modelling. The thermo-mechanical performances of the connections are determined using two different meshing and calculation procedures. The thermal model meshing is continuous to take the thermal continuity between the connection components into account. Regarding mechanical and thermo-mechanical calculations, the meshing is discontinuous to consider the gap and the contact changes between the connection components. The thermal model takes into account the evolution of physical properties of materials as a function of the temperature and is calibrated according to the experimental measurements. The thermo-mechanical model considers the mechanical properties – temperature evolutions of the materials provided by the corresponding Eurocodes. The thermal model can predict the temperature fields inside the connection components. Its validation is conducted through comparison with the experimental temperatures measured in different places inside the connections. The mechanical model is validated using the experimental load–slip curves of the connections in standard conditions. Finally, the thermo-mechanical model is validated by considering the global time–slip curves and by determining the fire resistance rating of the connections. A good agreement is obtained between simulated fire resistance times and experimental ones.

► Experimental and numerical Thermo-mechanical behaviour.
► Timber-to-timber connections subjected to tension in parallel to wood grain and to fire.
► Numerical FEM model is developed to analyse the thermo-mechanical behaviour of connections.
► Numerical validation by comparisons with experimental results; in standard and fire exposure conditions.
► Results are used to calibrate a simplified formula for engineer's practical use.