Experimental and numerical investigation of the flexural behavior of a novel steel-concrete composite beam system

This paper presents an experimental and numerical study on the flexural behavior of a new composite beam system. The system is composed of I-shaped steel beams, partially encased in reinforced concrete and filled with rock wool insulation. The experimental investigation included three large-scale composite steel-concrete beams and one steel beam as a reference. Key variables such as the thickness of the concrete layer and concrete strength were examined. The study focused on analyzing failure modes, load-deflection curves, and the strain distribution in both the concrete and steel sections. The experimental results indicate that the composite beam system significantly outperformed the reference steel beam. Notably, the proposed composite beams demonstrated an initial stiffness that was about 70% higher, a yield strength improvement of approximately 61%, and an ultimate load capacity increase of around 65%. These enhancements highlight the effectiveness of the composite design in enhancing structural performance. The composite beams also exhibited a ductility ratio exceeding 5 and confirmed linear strain distribution along the beam height, validating the plane section assumption. Additionally, a numerical model was developed and validated using the experimental results, which highlighted that design factors such as steel strength and section dimensions are more critical than concrete strength in optimizing the composite beam system.