考虑混凝土损伤和钢筋屈服的海上单桩基础水平承载特性数值分析

Numerical Analysis of Lateral Bearing Behavior of Offshore Single Pile Considering Concrete Damage and Reinforcement Yielding

采用三维非线性有限元方法对水平荷载作用下海上单桩基础力学响应进行了比较系统的数值分析.桩身混凝土采用弥散开裂模型,钢筋采用基于Mises屈服准则的理想弹塑性本构模型.首先对已有的基桩水平静载原位试验进行了数值模拟,计算结果与相关试验数据比较吻合.进而探讨桩周土内摩擦角、变形模量、桩体配筋率及竖向荷载水平等对海上单桩桩头水平位移与水平承载力的影响,结果表明:增大桩周土内摩擦角可有效提高桩基水平承载力.配筋率较低的单桩,其水平承载力容许值主要受桩身开裂控制,而对于配筋率较高的桩,水平承载力容许值受桩头水平位移控制.由上部结构物传递下来的竖向荷载有利于桩顶侧移的减小,但同时会增加桩身最大弯矩,最优竖向荷载水平为单桩竖向极限荷载的0.4~0.6倍.

The response of offshore single pile subjected to lateral loading is explored through three dimensional nonlinear finite element numerical analyses. In the analyses, non-linear behavior of concrete is modeled through smeared cracking model, and the strain-stress relationship of rebar is simulated using elasto-plastic constitutive model obeying Mises yield criterion. The finite element model is validated against published lateral static loading test in situ of single pile. The computed results agreed quite well with those from the in situ tests. The effect of internal friction angle and elastic modulus of soil, reinforcement ratio of pile, and vertical load level is investigated on the displacement of pile head and lateral capacity of pile. The results show that the lateral capacity of pile can be increased effectively in soil with higher internal friction angle. For the pile with low reinforcement ratio, the allowable lateral capacity is controlled by concrete cracking of pile, however the allowable lateral capacity is controlled by distortion of pile with high reinforcement ratio. The vertical load applied on the pile head may reduce its displacement, but increase simultaneously the maximum moment in the pile body. Therefore the optimum vertical load level is0. 4 -0. 6 times of the vertical ultimate load of a single pile.