Experimental study and theoretical analysis of glulam-concrete composite beams connected with ductile shear connectors

Ductile shear connectors are often applied in timber-concrete composite beams. The relative interface slip of such kind of composite beams will affect the mechanical performance of the composite beams and result in structural nonlinearity. Gamma method which adopts effective bending stiffness to reflect semi-rigid connection is recommended in Eurocode 5. The effective bending stiffness is irrelevant to external loads and calculation points of the composite beam. However, actual bending stiffness distribution along the beam is variable due to that shear connectors are subjected to different shear force. In order to verify the accuracy of gamma method, four-point bending tests of a total of three glulam-concrete composite beams with lag screw connectors and one pure glulam beam were conducted in this article. The failure mode, bearing capacity, and load–deflection relationship were investigated in the experiment. Meanwhile, push-out tests of composite beams were also conducted for determination of the force–displacement relationship of ductile shear connectors. Then, numerical simulation using beam-truss model was established for investigation on the mechanism of composite beams. Finally, theoretical analysis of composite beams considering the effect of interface slip was also presented. Comparing results from gamma method with the presented method, it is shown that both methods can calculate deflection at serviceability limit state with high precision. However, non-uniform distribution of actual bending stiffness cannot be reflected by gamma method.