Experimental and simulation study on the effects of corrosion and axial compression ratio on the seismic performance of railway pier columns under low-temperature freeze-thaw

In the saline soil areas of the Qinghai-Tibet Plateau, railway bridge piers suffer low-temperature freeze-thaw cycles (LFC, −40℃ to 20℃) and reinforcement corrosion. This study experimentally and numerically investigates seismic performance deterioration of reinforced concrete (RC) railway bridge piers under the combined action of LFC and reinforcement corrosion. Round-ended column specimens were exposed to 100 LFC and accelerated corrosion tests (corrosion ratio of 0–20.04%) in sequence to simulate the environmental actions, followed by quasi-static test with a low axial compression ratio of 5% to reflect the actual service conditions of railway bridge piers. Meanwhile, a finite element model was developed incorporating layered freeze-thaw damage in concrete and corrosion-induced material degradation, which was validated against the experimental results, and then the effects of axial compression ratio up to 15% were analyzed. The experimental results show that the increase in corrosion ratio leads to fewer cracks, obvious stiffness degradation, and severely pinched hysteresis loops. At a corrosion ratio of 20.04%, the peak bearing capacity dropped by 46.5%, and the ultimate displacement decreased by approximately 61.1%, with the total energy dissipation capacity reaching only 8.5% of that for the uncorroded one. The numerical analyses further indicate that an increase in the axial compression ratio is found to amplify the adverse effects of corrosion on the yield drift ratio, the ultimate drift ratio, and the post-peak softening rate. Based on the nonlinear effect decomposition model, a significant interaction between axial compression ratio and corrosion ratio is identified for the peak bearing capacity, with a negative interaction coefficient of 0.013, indicating a deterioration trend when high corrosion ratio (>10%) is combined with high axial compression ratios (>10%).