Experimental investigation of steel-timber shear connections with self-tapping screws
Brendan P. H. Deeves, Joshua E. Woods
Abstract
Steel-timber composite floor systems consisting of a cross-laminated timber (CLT) floor slab and steel wide flange beams rely on a shear connection at the interface between the steel and CLT to maintain composite action. This paper discusses experimental results on the behaviour of self-tapping screws (STS) as shear connectors for steel-timber composite beams and examines the influence of several parameters on their performance, including screw type, size (i.e., length and diameter), installation angle, and the performance of combined screwed and glued connections. Experimental results demonstrate that varying STS types and installation conditions result in significant differences in stiffness, strength, and failure mechanisms. In general, fully threaded STS exhibit more variability in their response and brittle failure modes, whereas partially threaded STS exhibit ductile failures with the more consistent and predictable performance. Due to their consistent performance and their ease of installation, partially threaded STS are likely the most suitable for steel-timber composite beams, and so, a load slip model was proposed to model their response. The results show that the proposed load-slip model can predict the stiffness and maximum load for partially threaded STS within 5 % of the experimental result on average over a range of screw lengths and diameters. Limitations of the model are also discussed. • Testing of self-tapping screws as shear connectors for steel-timber composite beams. • Influence of screw type, screw size, installation angle, and glued connections. • Screw type and installation angle influences the stiffness, strength, and failure mode. • An empirical model is proposed for the load-slip response of partially threaded self-tapping screws. • Empirical model can effectively capture connection stiffness and strength.