Bearing Capacity Evaluation and Reinforcement Analysis of Bridge Piles under Strong Earthquake Conditions

This paper investigates the Minjiang River Bridge No. 3 in Dujiangyan based on actual bridge tests and theoretical methods of analysis; here, we analyze the bearing capacity and the strengthening of the bridge. The detailed reinforcement measures for the bridge pile included the following actions: taking pile-patching measures on both sides of the severely scoured pile, adding bearing platforms, and adopting concrete-filled steel tube on the part of the pile leakage that lies above the current scour line. The bearing capacity evaluation of the bridge was performed before the reinforcement under strong earthquake and current scour conditions. After reinforcement, a bearing capacity evaluation for the bridge was performed under strong earthquake and current scour conditions using the load test for bridge piles. The analysis indicates that under current scour conditions, the maximum bending moments at the tops of piles 15-1, 15-3 and 16-3 are -4,824.5 kN.m, 5,206.9 kN.m, and 5,229.9 kN.m, respectively. These values are greater than the yield bending moment 4,787.7 kN.m obtained by the M-ϕ curve. Thus, the pile foundation will incur bending failure. The bearing capacity of the bridge after reinforcement can meet the design requirements and tends to be stable under the action of a strong earthquake. Through static load tests using vehicles, the maximum strain effect coefficient was 0.62, which meets the specific requirements for calibration coefficients (i.e., ξ ≤ 1.0). The maximum pier settlement was 0.01 mm, and the settlement tended to stabilize during the loading process. After unloading, the settlement nearly completely recovered, and the bridge foundation was stable; thus, the strengthening scheme is feasible. These results provide an important reference for bridge reinforcement in earthquake-prone areas and river erosion areas.