Experimental and numerical analysis of tensile properties in steel-timber bonded-screwed hybrid single-lap joints with different drilling directions

Cold-formed thin-walled steel and fast-growing natural timber systems are highly promising composite structures. This investigation conducted tensile experiments on single-lap joints to evaluate their connection's shear properties. Three types of connections were tested: bonded, screwed, and hybrid joints. Two drilling orientations were studied within the screw and hybrid joints: timber-to-steel and steel-to-timber, to explore their discrepancy in joint performance. Numerical simulations were conducted using the cohesive zone model and nonlinear contact. The research shows a significant difference in the joints' performance with two drilling directions. The timber-to-steel screwed joint had a 29% higher average peak load capacity than the steel-to-timber screwed joint, along with 40% differences in peak displacement. Secondly, the hybrid joint exhibits comprehensive advantages over other joints. Incorporating screws improved the safety and ductility of the joint compared to the bonded joint. Moreover, the adhesive layer delays the failure of screws, resulting in a slightly enhanced second peak load compared to the peak load capacity of the screwed joints. This study demonstrates the potential performance differences of screw configuration in drilling directions. Furthermore, the mutual gain of adhesive and screws shows hybrid joints' potential benefits and suitability for engineering applications.