水平及扭转荷载作用下群桩基础受力分析方法

Analysis method for pile groups subjected to lateral and torsional loads

江河与海上的大型结构在船舶撞击、风浪等作用下,其桩基础往往会受到水平及扭转荷载共同作用,极易造成基础倾斜倒塌。针对水平和扭转共同受荷下群桩基础,建立了由刚性承台–弹性梁–土非线性弹簧组成的群桩计算模型。通过水平p–y曲线法、竖向荷载传递法、扭转τ–θ曲线法,计算单桩非线性刚度;群桩各基桩间相互作用和基桩各自由度耦合,通过考虑p乘子和运用考虑推力弯矩影响的基桩受扭计算模型体现。结合牛顿迭代法,对计算模型进行求解,并与大尺寸物理模型试验结果进行了对比。通过参数分析表明在水平和扭转荷载共同作用下,群桩中各基桩桩头剪力分配不均性十分显著;并获得不同承台高度时群桩中基桩轴力变化规律,为复杂荷载下群桩设计提供依据。

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-y curve method in horizontal direction,the load transfer method and the τ-θ curve 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 p multiplier 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.