Flexural behavior of novel prestressed steel reinforced RPC composite beams with high-strength steel bars

A type of novel prestressed steel reinforced RPC composite beams with high-strength steel bars (PHSRCBs) is proposed by integrating the advantages of steel reinforced concrete structures and high-performance materials. To systematically investigate its flexural behavior, the reliability of the finite element modeling approach and constitutive models is first verified through comparison with available experimental results, and 28 full-scale finite element models are subsequently developed for parametric analysis. The results indicate that increasing steel content enhances the ultimate load-bearing capacity (N_u) and initial stiffness (K) but reduces the ductility coefficient (μ). Increasing the strength of constituent materials generally improves the flexural performance of PHSRCBs, among which the compressive strength of RPC (f_cu) shows the greatest influence on μ, resulting in an increase of up to 24.64% as f_cu rises from 90 MPa to 120 MPa. In contrast, the span-to-height ratio (L/H) also has a pronounced effect on structural performance, with a reduction from 14 to 8 increasing N_u and K by 41.36% and 67.65%, respectively. Based on the mechanical behavior analysis and load-deflection curve, the entire loading process of PHSRCBs is divided into four stages. The failure mode is mainly governed by the crushing of RPC in the compression zone. After reaching the peak load, the load-bearing capacity gradually decreases and stabilizes at a residual level, which is attributed to the crack-bridging effect of steel fibers in RPC and the continued contribution of steel components after yielding. Finally, based on current design codes and the principle of internal force superposition, simplified formulas for the short-term stiffness and ultimate flexural capacity of PHSRCBs are developed and validated, providing a reference for the preliminary design and analysis of this type of composite beams, although their applicability is confined to the investigated parameter range.