Full-scale test and numerical study on seismic performance of bridge piers with 650 MPa grade steel bars

This study employs full-scale pseudo-static cyclic tests and advanced numerical simulations to investigate the mechanical behavior and seismic performance of concrete columns reinforced with 650MPa-grade high-strength steel bars. Monotonic tensile testing demonstrates that HRB650E steel bars exhibit significantly higher yield and ultimate tensile strengths than lower-grade HRB400 and HRB500E specimens. And an improved shear strength model is proposed, which can enable precise prediction of the shear capacity for HRB650E reinforced concrete bridge piers, achieving a deviation margin within 3% of experimental values. A comparative analytical evaluation reveals that bridge piers incorporating HRB650E steel bars exhibit superior performance characteristics in structural performance assessments when compared to HRB400-grade reinforcement systems, with quantifiable improvements observed in critical metrics including load-bearing capacity, ductility, and energy dissipation mechanisms. Notably, the synergistic use of C70 high-performance concrete with HRB650E steel reinforcement demonstrates enhanced load-bearing capacity in bridge pier systems. Then, a four-segment piecewise model is developed through systematic parameterization of experimental skeleton curves, delineating sequential behavioral phases: elastic deformation, crack initiation, yielding plateau, and post-peak strength degradation. Numerical simulations in OpenSees successfully replicates the hysteretic behavior of HRB650E bridge piers. This systematic investigation establishes theoretical and practical foundations for next-generation high-performance reinforced concrete infrastructure design.