Yueying Zhang

Precast segmental reinforced concrete (RC) piers have been widely used in the construction of offshore bridges to speed up construction. Offshore bridges in cold regions are inevitably affected by the seawater freeze–thaw cycles under the periodic movement of tides, which could reduce the mechanical property of RC piers. Based on the low cyclic loading test on 12 specimens with different seawater freeze–thaw cycles, axial compression ratio, diameters of longitudinal reinforcement, and stirrup spacing, the hysteresis characteristics of precast segmental RC piers were analyzed. The test results show that the peak load decreased by 11%, while the peak displacement increased by 40% after 125 seawater freeze–thaw cycles. The hysteresis curves became fuller and the residual displacement became smaller with the accumulation of freeze–thaw damage. In the same 125 freeze–thaw cycles, the peak load increased by 15% and 27% while increasing the axial compression ratio and the longitudinal reinforcement diameter. Combined with the regression analysis of the experimental results, the restoring force model of RC piers considering the seawater freeze–thaw damage and design parameters was established, and the calculation method of each characteristic point in the model was given. The deviation values of flexural capacity are not more than 6.5%, and the deviation values of peak displacement are not more than 12%. The restoring force model determined in this paper could provide a reference for seismic response analysis of offshore bridges in cold regions.

The reinforced concrete (RC) piers of offshore bridges inevitably experience seawater freeze–thaw cycles due to the periodic movement of tides in cold climates. The damage caused by seawater freeze–thaw cycles will reduce the durability and mechanical properties of concrete, and then affect the seismic performance of RC piers. The method of seismic performance analysis on RC piers by numerical simulation is gradually emerging because the process of the conventional experiment is relatively complicated, and the heterogeneity and degradation of concrete after seawater freeze–thaw cycles should be considered. In this study, the method of meso-element equivalent and layered modeling was used to simulate a low cyclic loading test on an RC pier after seawater freeze–thaw cycles with ABAQUS software. The numerical simulation results were compared with the experimental results; the deviation value of peak load was not more than 6%, and the deviation value of peak displacement was not more than 10%. The result of the numerical simulation matched well with the experimental results, and the influence of different parameters was analyzed through the practical method of numerical simulation. It can be determined that the peak load decreased by 11%, while the peak displacement increased by 40% after 125 seawater freeze–thaw cycles. In the same 125 freeze–thaw cycles, the peak load increased by 15% and 27% while the axial compression ratio and the longitudinal reinforcement diameter increased. As the stirrup spacing of specimens decreased, the peak load remained unchanged, but the ductility coefficient of the specimens increased by 20%.