Thermo-hydric transfer within timber connections under fire exposure: Experimental and numerical investigations

Connections within timber structures are highly vulnerable areas when exposed to fire, especially when made of fasteners with different thermal and mechanical properties. This mechanical cohabitation can generate, because of material permeability differences, additional physico-chemical phenomena. These phenomena are affected by the coupling of heat and moisture transfers, which can alter the mechanical behaviour of timber structures. In order to improve our knowledge of the thermo-hydric timber connection, a series of experimental tests has been carried out and numerical models have been developed by taking the experimental observations into account. The experimental campaign concerns timber-to-timber and timber-steel-timber connections exposed to an “ISO 834” fire. The connections studied are real joints made of timber members, with and without a median metal plate, and maintained using bolts or dowels. The present study was conducted to examine heat transfer while taking the hydric effects at the interface between timber and steel fasteners into account. To analyse the experimental results and adjust the thermo-physical parameters for numerical modelling, numerical thermal fields, finite differences “FDM” and finite elements “FEM”, models are developed. Numerical and experimental results are in good agreement. Nevertheless, some observations are made and discussed by comparing numerical results with experimental ones.