Numerical and Analytical Assessment of Flexural Performance in Partially Encased Composite Steel Beams

This paper presents a comprehensive numerical and analytical investigation into the flexural performance of partially encased composite steel beams (PECSBs) subjected to bending loads. A total of 54 finite element (FE) models were developed to assess the influence of critical geometric and material variables on structural behavior. The numerical results were validated against available experimental data to ensure accuracy and reliability. The interaction between the steel and concrete components was simulated using a friction coefficient of 0.65, derived from prior experimental findings. As part of the study’s contributions, novel analytical equations were proposed to estimate both the ultimate flexural strength and the mid-span deflection of PECSBs. These equations are based on physical parameters and validated numerical outcomes, offering a practical tool for structural engineers. In addition, a new dimensionless indicator, termed the Composite Flexural Index (CFI), was introduced to quantify flexural efficiency under varying levels of composite interaction. The proposed models and the CFI metric offer a robust framework for performance-based design and optimization of composite beam systems. The findings enhance the understanding of key design sensitivities and contribute to improving stiffness, ductility, and overall structural reliability in PECSB applications.