Numerical Investigation of Displacement and Mechanical Responses of the Pile–Caisson Anchorage for Suspension Bridges

The pile–caisson anchorage (PCA) is a hybrid anchorage foundation for suspension bridges, combining the advantages of both caisson anchorages and steel pipe piles. This paper investigates the displacement and mechanical responses of the PCA under the main cable tension. Three-dimensional finite element models of the conventional caisson anchorage and the proposed PCA were constructed in PLAXIS 3D for a comparative analysis. The mechanical responses of the piles within the PCA were analyzed in detail, including lateral displacements, axial forces, and bending moments. Furthermore, a parametric study was carried out to explore the key parameters affecting the performance of the PCA. The results show that both the conventional caisson anchorage and the PCA strictly satisfy the code-specified displacement limits, with the safety factors of both anchorage systems reaching 2.5, confirming the feasibility of the PCA. The piles within the PCA exhibit pronounced spatial non-uniformity in displacement and internal force distribution. Moreover, increasing the caisson height significantly enhances the PCA’s overall stability, whereas enlarging the pile diameter and extending the pile length improve its structural performance through increased flexural rigidity and deeper mobilized shaft resistance, respectively. These findings offer valuable insights and practical guidance for the design and structural optimization of suspension bridge anchorage foundations.