海洋平台导管架结构分析中管节点局部柔度的等效单元

本文建立了一种在海洋平台导管架有限元分析中代表管节点局部柔度的等效单元,可有效地反映管节点在轴力和弯矩作用下的局部变形性质,并导出了T型、Y型以及K型管节点的局部柔度等效单元的刚度矩阵。本文建立的等效单元可方便地与通用结构分析有限元程序(如SAP5)配合,对海洋平台导管架进行计及管节点局部柔度的精确静动力分析。作者编制了与SAP5配合使用的前处理程序,可自动生成符合SAP5输入格式的等效单元读入刚度矩阵的数据。文中给出了说明等效单元应用方法的简单算例。与有限元法计算的结果比较表明,用等效单元模拟管节点的局部柔度是必要的和准确可行的。

Euqivalent Element Representing Local Flexibility of Tubular Joints in Structural Analysis of Jacket Structure of Offshore Platforms

At the tubular joint of a jacket structure of an offshore platform, the chord wall of the joint will deform locally after loading. Therefore, when the structure is analysed as a frame, beam elements are not rigidly connected at the joint. The local flexibility of tubular joints caused by the local deformation of the chord wall should be taken into account in the calculation. An equivalent element representing the local flexibility of tubular joints is developed in this paper, which can be used in the finite element analysis of the jacket structure of offshore platforms. The charactristics of local deformation of tubular joints under axial force and inplane bending moment can be effectively modeled with the equivalent element. Stiffness matrices of the equivalent elements for T-,Y- and K-type tubular joints arederived. which can be established after evaluating the values of the local flexibility by using parametric formulae. The equivalent element can easily be used together with the general FEM program, such as SAP5, to perform precise static and dynamic analysis for the jacket structure of offshore platforms. A preprocessing program for automatically generating data of the stiffness matrix of the equivalent element, which coincide with the input format of the readin-stiffness element in SAP5 element library, has been developed. A simple example is given to illustrate the practical use of the equivalent element. The results show that it is necessary to consider the local flexibility of tubular joints in the structural analysis of offshore platforms. Comparison of the results by using a model involving the equivalent element with those from a FEM calculation is also given. which indicate that it is viable and accurate to employ the equivalent element in modeling the local flexibility of tubular joints.