This paper extends the use of the skew boundary condition in two- and three-dimensional (3D) finite element analysis for both structural and geotechnical applications when the need of the freedom directions at the interface nodes is different from the global Cartesian directions. For instance, jack-up structures have three conical-shaped footings, whose freedom directions at the interface nodes are not suitable for Cartesian directions. In addition, there is no axisymmetric movement of the soil as the load is applied to the jack-up's hull. Thus, a more reliable solution of jack-up-soil interaction should be analyzed in a full 3D version. This paper develops a simple 3D interface model for soil-structure interaction that uses skew boundary conditions and incorporates the visco-plastic strain method into the finite element program. The work was validated by computing bearing capacity factors of conical footings with different scenarios, such as plane strain, axisymmetric and 3D analysis. The results of the present analysis are in good agreement with the existing solutions. The fields of the displacement vector and failure patterns at the collapse state are demonstrated and discussed for each apex angle, and the influence of the conical angle on the bearing capacity factor (N_c) is also examined.

当界面节点处的自由方向需要不同于全局笛卡尔方向时，本文扩展了斜边界条件在二维和三维 (3D) 有限元分析中的使用，用于结构和岩土工程应用。例如，自升式结构具有三个圆锥形基础，其界面节点处的自由方向不适合笛卡尔方向。此外，当负载施加到自升式船体时，土壤不会发生轴对称运动。因此，应该在完整的 3D 版本中分析更可靠的自升式土壤相互作用解决方案。本文为土-结构相互作用开发了一个简单的 3D 界面模型，该模型使用倾斜边界条件并将粘塑性应变方法纳入有限元程序。该工作通过计算具有不同场景的锥形基础的承载力系数来验证，例如平面应变、轴对称和 3D 分析。目前的分析结果与现有的解决方案非常吻合。展示和讨论了每个顶角的位移矢量场和坍塌状态下的破坏模式，以及锥角对承载力因子的影响（N _c ) 也被检查。