正交异性钢桥肋-桥面板焊缝裂纹的三维断裂力学分析

正交异性钢桥的肋-桥面板焊缝处的疲劳裂纹是典型的三维裂纹问题,但是现在普遍采用平面应变二维裂纹模型对其进行断裂力学分析.基于Schwartz-Neuman交替法建立正交异性钢桥肋-桥面板焊缝裂纹的局部三维断裂力学分析模型;评估焊缝处表面裂纹的形状和深度对应力强度因子的影响;采用Paris公式估算等应力幅下焊缝的疲劳寿命.计算结果表明:用平面应变二维裂纹模型进行正交异性钢桥的肋-面板焊缝的断裂力学分析会严重低估其疲劳寿命;采用三维断裂力学模型进行肋-桥面板焊缝裂纹的疲劳寿命分析十分必要.

3D fracture mechanics analysis on cracks at rib-deck weld joints of orthotropic steel bridge

The fatigue crack at the rib deck weld joints of orthotropic steel bridge is a typical 3D crack problem. However, the 2D plane strain crack models are widely used to perform the fracture mechanics analysis. Based on the Schwartz Neuman alternating method, a local 3D fracture mechanics analysis model is built for the rib deck weld joints of an orthotropic steel bridge; The effect of the depth and shape of surface cracks at the weld joint on the stress intensity factors is evaluated; the fatigue life of the crack is estimated using Paris equation under the assumption that the stress intensity factors range could be treated as an equivalent constant value. The calculation results indicate that, the 2D plane strain fracture model adopted for the cracks at the rib deck weld joints of orthotropic steel bridge significantly underestimates the fatigue life, and it is necessary to use 3D fracture mechanics model to analyze the fatigue life of rib deck weld joints.