Innovative shear connectors for composite cold-formed steel-timber structures: An experimental investigation

An experimental investigation into the behaviour of bespoke shear connectors designed to generate composite action in cold-formed steel-timber structures is presented. The response of the shear connectors was assessed through a comprehensive set of push-out tests, where the cold-formed steel thickness and the connector type and material were varied. Previous studies have shown that while the use of ordinary self-drilling screws as shear connectors enables the development of some composite action, their performance was inhibited by timber embedment. Hence, the main feature of the innovative shear connectors was the introduction of a fitting around the screw to mobilise higher timber embedment forces. The best performing shear connectors achieved about double the shear resistance, four times the initial slip modulus ks and seven times the mid-range slip modulus ks,m of ordinary self-drilling screws. An analytical model presented in previous research was extended to describe the response of the innovative shear connectors developed in this study. The model was validated against the push-out test results, and shown to be able to accurately predict the ultimate load, slip at ultimate load, and the two slip moduli ks and ks,m of the innovative connectors, with mean model-to-test ratios of 1.01, 1.15, 1.29 and 1.19 respectively.