Glued-in steel plate and screwed connections in Timber–Concrete Composites systems: Mechanical performance and design implications

This paper presents a comparative study between Timber–Concrete Composite (TCC) systems with glued-in steel plates and screwed connections. The research focuses on evaluating the structural performance of these connections, with a particular focus on the innovative glued-in steel plate through full-scale four-point bending tests on floor subassemblies with a 7.5 m span, complemented by push-out tests for assessing the behaviour of the slab-beam connection. The study aims to determine if the glued-in steel plate, a more economical option, can replace screws without significantly compromising the TCC system's stiffness or strength. The findings reveal that while the glued-in steel plate connections exhibited lower stiffness and ductility compared to screwed connections, they demonstrated a significantly higher load-bearing capacity. Specifically, the glued-in connections achieved capacities ranging from 670-720 kN, markedly exceeding the 300-350 kN and 480-520 kN capacities of specimens with fewer and more screws, respectively. These results suggest that glued-in steel plate connections can effectively replace screws in TCC systems, offering a cost-effective alternative without significantly reducing structural integrity. Moreover, the paper evaluates how to design TCC floors by estimating the effective number of connectors and the effective length of the glued-in steel plate using an iterative γ-method. This is done to account for changes in stiffness, as determined from push-out tests and observed in bending tests. The iterative γ-method's findings have been validated against the predictions of a Finite Element model.