Experimental and finite element analysis of flexural performance of steel-timber composite beams connected by hybrid-anchored screws

The shear connection between the steel and the timber slab is one of the keys to designing steel-timber composite (STC) beams. By three groups of four-point bending tests and finite element simulations, the effects of hybrid anchorage and filling materials on the flexural performance of STC beams were investigated. Firstly, compared with the STC beam connected by ordinary screws, when epoxy resin and mortar were respectively used as the filling material in the STC beams connected by hybrid-anchored screws, the slip stiffness values were increased by 18.79% and 48.40%, the capacity values were increased by 10.13% and 15.15%, and the maximum end slip values were reduced by 8.77% and 8.97%, respectively, indicating that mortar was more effective. Secondly, due to the strong restraint provided by the filling material and the H-steel flange for the screw tip and head, respectively, double plastic hinges were generated in the screw, and the development of double plastic hinges at both ends of the simply supported STC beam is more significant. Thirdly, finite element analysis showed that the mortar strength (greater than 30 MPa) had little effect on the flexural performance of STC beams connected by hybrid-anchored screws; increasing the number of hybrid-anchored screws can significantly improve the slip stiffness of the connection interface of STC beams and reduce the slip.