Analysis method for pile groups subjected to lateral and torsional loads

Pile group foundations of large structures on the water are usually subjected to lateral and torsional loads induced by ship impact or waves, which can even cause their collapse. A hybrid model for pile groups including a rigid cap, elastic beams and nonlinear springs of soils is proposed. The nonlinear stiffness of each pile is computed by using the p-ycurve method in horizontal direction, the load transfer method and the τ-θcurve method in vertical direction, respectively. Pile group effect and load coupling effect among the degrees of freedom in pile head are considered by means of the pmultiplier and the analysis method for a single pile under torque coupled with lateral load and bending moment. The pile group model is solved by use of the Newton’s iterative method, and the results are verified through large-scale model tests. Additionally, parametric analysis is carried out as well. It is found that the distribution of shear force in each pile head is observably nonuniform. The variation of axial force of each individual pile in the group with different free lengths is presented. The study may support the design of pile groups subjected to complicated loads.