A new type of structural element, the timber-concrete composite beam, exhibited excellent structural performance. The notched connector is widely used in timber-concrete composite systems as a result of its considerable shear capacity and stiffness. Six groups of push-out tests were performed to investigate the shear performance of the notched connectors for the timber-concrete composite beams, with consideration to the varying concrete types, the shear length of the timber, and whether the notch was reinforced. From the test results, the notched connectors that corresponded to the shear fracture of concrete or timber had a low shear capacity and poor ductility. Notched connectors that simultaneously failed at the concrete slab (via shear force), as well as at the lag screw reinforcement point during bending presented the greatest shear capacity. This was followed by the notched connectors that exhibited diagonal-compression failure at the concrete slab. Screw fasteners in the notch were shown to improve the strength, ductility, and post-peak behavior of the notched connectors. In addition, the concrete type, the shear length of the timber, and whether the notch was reinforced were found to have no major influence on the slip modulus of the notched connectors.

In order to investigate the mechanical behavior of the partially concrete encased composite beam under hogging moment, static loading tests were conducted on one conventional composite beam and three partially concrete encased composite beams. The results show that partially concrete encased composite beams have higher stiffness and flexural capacity under hogging moment as compared with conventional composite beams. It is also found that the concrete encasement is able to enhance the local bucking resistance of the steel beam and effectively reduces the propagation speed of crack width under hogging moment. By comparing different partially concrete encased composite beams, it is indicated that the stiffness and flexural capacity of partially concrete encased composite beams increase with the increase in reinforcement ratio of the concrete slab. Also, with the increase in the reinforcement ratio of the concrete slab, the distribution of cracks on the slab is denser and the propagation speed of crack width reduces. In addition, the calculation methods in both European code and Chinese code can well predict the crack width on the concrete slab, and the ultimate flexural capacity predicted from the simplified plastic theory in Eurocode 4 is in good agreement with test results.

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.