Study on the flexural behavior of double-C light steel partially encased steel fiber-reinforced self-compacting lightweight concrete beams

To address the limited research on double-C light steel partially encased steel fiber-reinforced self-compacting lightweight aggregate concrete (DCPSLC) beams, this study investigates the influence of the section aspect ratio ( h / b ), the strength grade of steel fiber-reinforced self-compacting lightweight aggregate concrete (FSLC), and the reinforcement ratio on the flexural performance of DCPSLC beams. Four-point bending tests were conducted to systematically examine the failure modes, load–deflection responses, and strain developments of the specimens. Based on a validated finite element (FE) model, the stress distribution characteristics of the light steel skeleton and concrete were analyzed, and the influences of the light steel strength grade and thickness on the flexural performance of the beams were investigated. In addition, a theoretical model for calculating the flexural bearing capacity of the DCPSLC beam section was derived. The results indicate that the influence of h / b and reinforcement ratio on the initial stiffness and flexural bearing capacity are more significant than that of the FSLC strength grade. The DCPSLC beams exhibited favorable post-yield plastic deformation capacity ( γ p = 1.11–1.35). The displacement ductility coefficient μ decreased with increasing h / b , but increased with higher FSLC strength grade. The strain distributions along the section height at different stage of load were approximately linear, which generally conforms to the plane-section assumption. Increasing the reinforcement ratio effectively restrained crack propagation in the FSLC. The FE analysis indicates that configuring longitudinal reinforcement in FSLC contributes to the dispersion of internal stresses; the flexural bearing capacity increases with the rise of h / b , the strength grade, and the thickness of the light steel. The theoretical calculation values of the flexural capacity of the normal section are in good agreement with the experimental results, which can provide a theoretical basis for the design and application of this kind of composite beams.