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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.

An experimental investigation into the behaviour of connections between cold-formed steel and timber components, formed with inclined screws, is presented. A series of material tests was firstly carried out to assess the behaviour and limitations of each component of the system under investigation. These were supplemented by three types of interaction test: timber embedment, screw head pull-through and screw thread withdrawal, all aimed at developing a better understanding of the behaviour of the different components of the connection. The slip modulus and peak load-carrying capacity of twelve connection configurations were determined through a series of push-out tests. The results obtained were compared to the typical benchmark arrangement in which the screws were driven in perpendicular to the steel-timber interface. Component variations included the type of timber – particle board and plywood, the thickness of the steel – 1.5 mm and 2.4 mm thick, the inclination of the screws – 0° and 45°, and the presence or not of wings on the screws. The results showed that non-winged screws inclined at 45° gave up to about a 30% increase in peak load-carrying capacity and about a 140% increase in slip modulus when compared to the reference specimen.

An analytical model that can describe the load-slip response of cold-formed steel-to-timber connections, based on three components: timber embedment, screw bending and the axial pull-through, is presented. The model takes into consideration the screw inclination and the damage to the timber caused during the screw drilling process. The model was validated against available push-out test results, where it was shown that the model can accurately describe the ultimate load, the slip at ultimate load, and the two slip moduli, ks and ks,m, with mean model-to-test ratios of 1.01, 1.03, 1.09 and 0.96, respectively. The observed failure modes were also accurately predicted. Comparisons between the test data and the predictions of the EN 1995-1-1 design expressions showed that the Eurocode underestimated the ultimate loads by around 50% on average and overestimated the slip moduli by around 500% on average; the proposed model therefore offers a significant improvement over current design provisions.