A three-dimensional finite element model for locally reinforced timber joints made with hollow dowel fasteners

Brittle premature failure caused by splitting parallel to the timber grain is a common failure mode in glulam joints made with solid dowel type fasten ers. It is thought that this problem can be alleviated by using hollow stee l dowels as the fasteners and reinforcing the timber locally in the area of the joint. In this way, by varying the wall thickness of the dowels and th e thickness of the reinforcing members, a chosen combination of strength an d stiffness should be attainable together with a ductile failure mode. In t his paper, three-dimensional nonlinear finite element models are developed to simulate (i) the structural performance of a timber joint made with a si ngle hollow steel dowel and (ii) a moment transmitting joint made with a nu mber of the dowels, each type being locally reinforced by densified veneer wood. The models incorporate suitably defined elastoplasticity and orthotro pic elasticity and also allow for large deformations of the joints as well as for frictional contact between the timber and the dowel. They are calibr ated against physical test data from joints loaded to failure.