Cyclic behaviour of bolt and screw shear connectors in steel-timber composite (STC) beams

Abstract

Feasibility and acceptable performance of the steel-timber composite (STC) system as a sustainable alternative to conventional steel-concrete composite have been demonstrated through recent static push-out and bending tests. But, structural behaviour and energy dissipation capacity of the STC connections subjected to cyclic loads have not been investigated yet. This study investigates the cyclic behaviour of STC connections with mechanical shear connectors. In total, twelve STC joints were fabricated by connecting the cross-laminated timber (CLT) panels to the flanges of a steel profile and the joints were subjected to low-cycle high-amplitude loading regime. Effects of the shear connector type (i.e. screw, high strength bolt), shear connector size and the orientation of CLT panels (outer lamellas parallel and/or perpendicular) with respect to the direction of the load were considered in the experimental program. The ductility, strength impairment and equivalent viscous damping which characterise the performance of a mechanical shear connector under cyclic loading conditions in steel-timber composite connections were assessed. The results of the cyclic tests demonstrated the high ductility and energy dissipating capacity of the steel-timber composite connections. A simple hysteretic model was proposed for steel-to-CLT composite connections with bolt and screw shear connectors and the model was calibrated against the results of laboratory experiments.