Abstract: Currently, the semi-empirical design method based on the linear elastic analysis assumption is commonly employed, which is incapable of examining the stability of the long pile embedded in complex ground mediums accurately. To this, this research adopts the nonlinear finite element method to establish an efficient pile element model for nonlinear analysis of piles. This approach can be utilized in nonlinear buckling stability analysis without assuming effective length factors. This paper elaborates the basic theory of the pile element. It’s worth noting that, the continuous springs along the element are integrated into the pile element formulations for considering the soil structure interaction (SSI) responses, which can significantly improve the computing efficiency. The element tangent stiffness matrixes are accordingly formulated for predicting displacement, and the secant relations are developed for eliminating accumulative errors in a Newton-Raphson incremental-iterative numerical procedure. The Updated- Lagrangian (UL) approach is developed for simulating large deflections of piles. Finally, several benchmark examples are provided for verifying the accuracy and efficiency of the proposed pile element model in analysis and design of piles with nonlinear surrounding soil.

Key words: single pile, finite-element, soil structure interactions, pile element, p-y curve