Performance of helically shaped metal fasteners in timber

This paper presents an experimental investigation into the withdrawal resistance of a new connector type for use in structural timber. The structural performance of several helically shaped metal fasteners, which for some years have been used as wall ties and in masonry repairs, are investigated for use in a variety of timber connection systems. This paper describes part of a research programme investigating the withdrawal resistance and behaviour of these fasteners compared with conventional nails. It also details the effects of predrilling, density of timber, depth of penetration and timber grain orientation on the withdrawal resistance of these fasteners. The results show that helically shaped metal connectors achieve greater withdrawal resistance and exhibit a more ductile behaviour than common nails. A semi-empirical model is developed to predict the withdrawal performance of the fasteners.