Response of combined formwork construction with precast concrete laminated slab and steel truss to flexural loading

Abstract This paper presents a precast concrete composite slab-steel truss formwork system incorporating demountable joints to achieve composite behavior between the upper slab and the lower truss, thereby facilitating truss reuse. The system enables shoring-free construction for medium to long spans(3.0m~6.0m), enhancing construction efficiency and reducing material consumption. To assess its performance under realistic conditions, three full-scale specimens were subjected to vertical static bending tests involving a loading-unloading procedure. A finite-element model was developed and calibrated against experimental results, followed by a parametric analysis. The system demonstrated excellent flexural performance with minimal residual deformations after unloading, indicating high recoverability and reliable reusability. Parametric studies reveal that increasing slab thickness primarily enhances the slab's behavior with negligible influence on the global structural response, whereas truss height and member cross-sections predominantly govern overall stiffness and load-bearing capacity. Based on experimental and numerical findings, simplified design equations for strength and deflection are proposed to support design optimization and practical implementation.