Numerical and fracture mechanics-based simulations of brittle failure modes in dowelled timber connections loaded parallel to the grain

For the design of robust timber buildings, it is essential to develop reliable methods to assess possible brittle failure of connections. Therefore, this paper proposes a three-step modelling approach to predict: (i) the load–displacement behaviour of individual dowels, (ii) the stress distribution in the timber matrix, and (iii) the brittle failure of the timber, in connections with laterally loaded steel dowels. The local nonlinear behaviour of single-dowel connections was determined with a Beam-on-Foundation model and subsequently assigned to nonlinear springs located at the multiple-dowel connection shear planes. The timber member and the steel plate were modelled using 3D shell elements with linear-elastic orthotropic and isotropic material properties, respectively. The interaction between dowels and shell elements was characterised by hard contact and friction. A post-processing module, based on linear elastic fracture mechanics, was implemented to evaluate potential cracks along the grain direction through the mean stress approach. The numerical model aligns well with previous experimental results and provides a novel approach for the prediction of crack initiation based on a realistic load distribution in multiple-dowel connections, while taking advantage of high computational efficiency.