Internal Force Distribution Characteristics of Top-Chord-Free Vierendeel-Truss Composite Slab

In modern construction, there is a growing demand for floor systems that offer high spatial efficiency and easy integration of mechanical, electrical, and plumbing (MEP) services. The top-chord-free Vierendeel-truss composite slab (TVCS), which omits the steel top chord and diagonal webs, presents a promising solution by maximizing usable vertical space and accommodating large ducts. Due to the elimination of the steel top chord and diagonal web members, the TVCS differs significantly in structural composition from conventional steel truss–concrete composite floor systems. At present, there is a lack of in-depth research on the mechanical behavior and deformation characteristics of this type of floor system. This study aims to fill this gap by systematically investigating the internal force distribution characteristics of TVCS and establishing a simplified analytical approach for practical engineering. This paper first employs the finite element method to conduct a comprehensive analysis of the bending moments, shear forces, and axial forces in each component of this composite floor system. The results indicate that the internal force distribution in TVCS exhibits substantial differences compared to that in conventional truss-composite floor systems: certain chord members exhibit inflection points; abrupt changes in internal forces occur between adjacent chord segments; and significant differences exist between the internal forces in members near the supports and those near mid-span. For instance, a distinct difference is that chord segments adjacent to the supports contain inflection points, while those near mid-span do not. Subsequently, simplified formulas for calculating the internal forces in the TVCS are proposed and validated against experimental and numerical analysis results. The main technical contribution of this work is providing a practical and efficient calculation tool that simplifies the design process for TVCS, facilitating its safer and wider application.