Buckling of piles in cohesive soil supporting jointless bridges

Abstract

Soil-structure and especially soil-pile interaction is one of the main sources of complication in the analysis of jointless bridges. Because of the complexity of the problem, calculation of the critical buckling load of embedded piles has always been a concern to the designers since piles are relatively slender elements. In the current design method, for simplification it is assumed that soil reaction is a linear function of the lateral displacement. In this paper, a new approach is proposed which utilizes the energy method and incorporates p-y curves to estimate the critical axial load of piles embedded in cohesive soil. Pile head displacement is also incorporated into capacity calculation. In this method, the soil reaction is a nonlinear function of lateral displacement and can efficiently model the soil-structure interaction. The method is validated with experimental data for solving the governing differential equation along with calculation of buckling load. Results of parametric study reveal that buckling loads estimated by equivalent cantilever method are highly above the corresponding loads estimated by the energy method at relatively small pile head movement. Furthermore, for this condition it is shown that fully embedded piles will fail before reaching the estimated buckling load because of yielding; consequently, buckling analysis does not govern the design of piles fully embedded in cohesive soil. However for partially embedded piles, the buckling load may govern.