轴向载荷下多平面DT型管节点应力集中系数概率模型研究

应力集中系数作为一个随机变量,对管节点及导管架平台的疲劳可靠性评估结果有着重要影响。文章以多平面DT型管节点为研究对象,建立了352个几何参数不同的三维管节点有限元模型,并分析了沿弦管-撑管焊缝处的应力集中系数分布。采用密度直方图描述最大应力集中系数统计样本的特征,利用疲劳可靠性分析中常用的几种概率分布进行拟合。各个概率模型中的参数通过极大似然估计方法得到。根据卡方检验的结果对比发现,Birnbaum-Saunders分布是最适合的概率模型。因此,文中提出一组适用于描述在轴向载荷即单向轴向和平衡轴向载荷作用下多平面DT型管节点弦管侧和撑管侧最大应力集中系数分布的概率模型,对今后导管架式海洋平台结构的疲劳可靠性分析具有重要意义。

A Probability Distribution Model for SCFs in Multi-planar Circular Hollow Section DT-joints Subjected to Axial Loading

Stress concentration factor (SCF) is considered as one of the random variables which great-ly affect the results of fatigue reliability assessment for the tubular joints and offshore jacket-type platform structures. In this study, 352 three dimensional finite element (FE) models of multi-planar circular hollow section (CHS) DT-joints with different geometric parameters are generated and the SCF distributions along the chord-brace intersection are analyzed. Several probability models com-monly used in the fatigue reliability analysis are fitted to the density histograms for statistical sam-ples of maximum SCFs. The values of parameters in each probability model are estimated by maxi-mum likelihood (ML) method. After the chi-squared goodness-of-fit test is performed, the Birn-baum-Saunders distribution is found to be the best fitted one. A set of probability density functions (PDFs) following Birnbaum-Saunders distribution are proposed for the maximum SCFs on the chord and the brace sides under two kinds of axial loading, i.e. single axial loading and balanced axial load-ing, respectively.