The steel–concrete–steel (SCS) sandwich composite structures with orthogonal longitudinal and transverse (bidirectional) steel webs exhibit superiorities in strength, ductility, impact resistance, blast resistance, and construction efficiency compared with the traditional engineering structures, offering a competitive alternative for applications such as submarine tunnels, nuclear shells, protective structures, offshore structures, etc. While there were several practices in engineering, the current design method is an application of the concrete code and there are few experiments that could support the design theory especially for the shear resistance. Unlike RC beams or steel beams, the SCS composite structures with bidirectional steel webs have multiple shear force transferring mechanisms, and it is of importance to investigate the contributions of the different mechanisms and how they work together as a composite structure. To address this problem, 16 shear tests of SCS composite structures with bidirectional steel webs were carried out and theoretical analysis was conducted. The shear resistance is categorized into three mechanisms: the composite truss, the pure shear of the axial web, and the dowel action of the flange. Then the theoretical method to predict the shear resistance considering the coworking of different mechanisms is proposed and compared with existing methods. It is proved that the proposed method reveals the antishear mechanism and is of satisfactory accuracy.

Reliable connections between steel beam and concrete slab are important for composite beams. A new type of uplift-restricted and slip-permitted T-shape (URSP-T) connector with foamed plastic was proposed to improve mechanical performance of the hogging moment region in composite beams, i.e., to prevent concrete slab separation from the steel beam and to delay the cracking of concrete. To investigate the slip and uplift performance of URSP-T connectors, six pushout tests and three pullout tests were conducted. In pushout tests, obvious slip deformation of the URSP-T connector occurred and the foamed plastics around connectors significantly affected the slip performance. It was observed from load-deformation hysteresis curves that stiffness changed with loading history. Based on the Richard-Abbott curve, a new hysteresis model was conceptualized to simulate the slip mechanism of the connector. The predicted results correlated well with test data. In uplift tests, two types of failure modes, i.e., punching shear failure of concrete and failure of the connector’s webs, were observed. Based on test results, the relationship between uplift performance and dimensions of the connectors is discussed. Furthermore, a design formula for ultimate uplift capacity and construction details of this connector is proposed. Pushout tests and pullout tests indicated that URSP-T connectors have excellent performance. Meanwhile, finite-element analysis proved that URSP-T connectors permit larger slip deformation and reduce tensile stress inside concrete in the hogging moment region of composite beams. The investigation reported in this paper may provide a basis for design and application of URSP-T connectors.