A precast bottom slab with additional stiffener of composite slab connected without gaps: Design approach and experimental investigation

Concrete composite slabs are extensively employed in assembled structures, due to their combined benefits from both assembled and cast-in-place slabs. Addressing concerns regarding the cumbersome fabrication, inconvenient transportation, and high cost associated with current composite slabs, this study proposes a new approach: integrating additional steel-tube-truss stiffeners (ASTTSs) into the precast bottom slab of composite slabs. Stiffeners are positioned beneath the bottom slab to enhance its stiffness during transportation and construction. This not only enhances the crack resistance of the slab, but also minimizes the need for bracing during construction. A design method for the precast bottom slab with ASTTSs is developed, and three bottom slabs with their corresponding stiffeners are designed, customized for different spans. Test results demonstrate that the precast bottom slab with additional stiffeners meets the construction stage requirements. The subsequent analysis of the test results not only validates the feasibility of the design method proposed in this study, but also elucidates the relationship between the additional stiffener and the equivalent stiffness of the specimen. The findings of this study offer a reference for enhancing the industrialization of composite slabs.