Flexural performance study and strain inversion-based composite action analysis of LW-PEC beams

Abstract

This study combines H-section steel (H-SS) with large width-to-thickness ratios of plates (some exceeding China's code (T/CECS 719–2020) limits) and lightweight aggregate concrete (LWAC) to form lightweight partially-encased composite steel and concrete (LW-PEC) beam for self-weight reduction. Four-point bending tests were conducted on 8 LW-PEC beams and 4 steel beams, considering link spacing and width-to-thickness ratios of plates. Based on the experimental data, an innovative analytical method for evaluating the composite action of LW-PEC beams was proposed and validated through experimental results. The experimental results show that LW-PEC beams exhibit distinct failure modes from steel beams: H-SSs in the LW-PEC beams flanges buckle upward due to LWAC and link constraints, with buckling severity related to link spacing and width-to-thickness ratios of plates. Furthermore, LW-PEC beams demonstrate improved load-bearing capacity and ductility compared to steel beams. Link spacing has limited influence on load-bearing capacity but affects ductility depending on width-to-thickness ratios of plates, where smaller ratios combined with closer link spacing produce enhanced ductility. Composite mechanisms analysis reveals that H-SS in LW-PEC beam contributes approximately 90 % of the load-bearing capacity, while LWAC primarily constrains steel deformation to enhance plastic development of H-SS in the LW-PEC beam, thereby enhancing the overall load-bearing capacity of the LW-PEC beam. The research findings enable the optimization of material utilization efficiency in LW-PEC beam design, offering valuable insights for exploring efficient and lightweight design methodologies of LW-PEC beams.