Seismic behavior of bridge columns with FRP-reinforced ECC at plastic hinge zones

Abstract

The plastic hinge region of bridge columns dissipates seismic energy under earthquakes, effectively constraining the extent of structural damage through localized plastic deformation. To enhance the seismic resilience of this critical region, this study proposes replacing the conventional concrete in the plastic hinge zone with engineered cementitious composite (ECC) and externally wrapping it with fiber-reinforced polymer (FRP). This approach is expected to significantly enhance structural damage tolerance, mitigate longitudinal bar buckling and steel reinforcement corrosion. The seismic performance of this new type of bridge column was investigated via quasi-static tests. The parameters were FRP type (large rupture strain FRP and traditional glass FRP) and the number of FRP layers (1, 2, and 3 layers). The combination of ECC and FRP exhibited outstanding seismic performance in terms of ductility, energy dissipation capacity, and damage control capacity. The existing equivalent plastic hinge length expressions of FRP-confined reinforced concrete (RC) members were evaluated and the proposed formula considering the confinement stiffness for FRP-confined ECC bridge columns delivered more accurate predictions. Nonlinear finite element analysis was performed and was shown to reproduce the hysteretic curves of the column models with acceptable accuracy. A parametric study was conducted to further analyze the effects of the wrapping height of FRP, axial compression ratio, and longitudinal reinforcement ratio on the peak lateral force and ductility of FRP-reinforced ECC bridge columns. Finally, design recommendations were provided for the engineering design of FRP-reinforced ECC structures.