方型鸟嘴式十字节点在支管非对称轴力作用下的应力集中特性研究

Stress concentration in square bird-beak X-joints under asymmetric brace axial forces

基于有限元分析对方型鸟嘴式十字节点在支管非对称轴力作用下的应力集中特性进行研究,得到热点区域的应力集中系数（SCF）及其分布规律,并与传统正放式节点的分析结果对比.选用典型无量纲参数建立节点的有限元模型,并采用实体单元模拟焊缝的几何形状.结果表明：对于单侧支管轴力工况,CIDECT疲劳设计指南中针对传统正放式十字节点的SCF叠加公式并不适用于方型鸟嘴式节点,原因在于后者的主管壁板之间存在更明显的相互作用,从而导致节点的非支管轴力侧也产生显著的应力集中.通过引入新的荷载工况X-BFam来考虑纯单侧支管轴力作用,提出了同时适用于传统正放式和方型鸟嘴式十字节点在支管非对称轴力作用下的SCF叠加修正公式.

The stress concentration factors（SCFs）and their distributions of square bird-beak square hollow section（SHS）welded X-joints under asymmetric brace axial forces were numerically investigated by finite element method.Typical non-dimensional parameters of tubular joints were introduced into the FE model,where the welds were simulated by solid elements.Results show that the existing superposition approach for the SCF calculation of conventional X-joints under single-side brace axial force,as provided in CIDECT fatigue design recommendation,can not be used for square bird-beak X-joints.The reason lies in that the chord wall interactions of square bird-beak X-joints are much more significant than the conventional ones,which would lead to remarkable stress concentration on the unloaded brace side of the bird-beak joints.By introducing a new load case X-BFam to represent the pure single-side brace axial force,a modified superposition formula was finally proposed for the SCF calculation of both conventional and square birdbeak X-joints under asymmetric brace axial forces.