Steel-timber composite beam-to-column joints: Effect of connections between timber slabs

Studies of steel-timber composite (STC) connections and STC beams under sagging bending have been reported elsewhere in the literature using push-out and four-point bending tests respectively. However, the structural behaviour of STC beam-to-column connections under hogging bending moments (with the prefabricated timber slabs in tension) have hitherto not been investigated. In particular, the connection between the two prefabricated timber slab panels (across the column) has a major influence on the structural performance of a STC beam-to-column connection and is the focus of the current study. Eight full-scale STC beam to steel column cruciform specimens with different connections (half lap, single and double surface spline with timber and/or steel plate) for the timber slabs were fabricated and tested under a monotonically increasing downwards displacement, and these are described in this paper. The bending moment capacity, rotation capacity, failure mode, stiffness and ductility of the STC connections are evaluated and discussed. The composite steel-timber system exhibits both appreciable ductility and rotation capacity which fulfil the existing design requirements for semi-rigid composite connections in Eurocodes EC3 and EC4. Furthermore, the negative bending moment capacity of STC connections is significantly higher than that of bare steel connections without a timber slab.