Experimental and numerical investigation of tension-bending coupling behavior and design-oriented predictive models for FRP cables

In this study, the tension-bending coupling behavior of fiber-reinforced polymer (FRP) cables was investigated through experimental testing, finite element modeling, parametric analysis, and sensitivity evaluation. Three representative cable configurations, including BFRP smooth tendons, CFRP smooth tendons, and BFRP flexible cables, were examined under different prestress levels and loading configurations. The results show that increasing prestress enhanced the initial flexural stiffness but accelerated stress accumulation, resulting in reduced deformation capacity and earlier brittle failure. Compared with low-prestress specimens, the ultimate deformation capacities of BFRP and CFRP smooth tendons decreased by approximately 22% and 37%, respectively. Compared with the test BFRP smooth tendons, the tested BFRP flexible cables exhibited 36.6–49.4% greater deformation capacity and more progressive failure behavior. Double-point loading increased the initial equivalent stiffness of BFRP smooth tendons and flexible cables by 43.3% and 36.8%, respectively, but reduced their strength utilization ratios by 11.7% and 9.4%. The validated pre-failure FE model captured the deformation pattern and stress redistribution. Parametric and sensitivity analyses identified cable diameter, prestress level, and core stiffness ratio as the dominant factors controlling deformation resistance, stress amplification, and stress redistribution, respectively. Two model-based relationships were further developed for preliminary prestress optimization and deformation assessment.