铁路正交异性钢桥面板典型疲劳裂纹寿命估算

针对铁路正交异性钢桥面板中典型疲劳裂纹形式,建立计算模型。采用有限元数值方法模拟钢桥面板应力分布,确定各典型疲劳裂纹最不利位置;利用有限元子模型技术模拟各疲劳裂纹位置焊接细节,分析焊缝引起应力集中程度及对疲劳裂纹产生所造成影响;依据断裂力学揭示疲劳裂纹扩展速率与裂纹周围应力场关系,对几种典型疲劳裂纹进行疲劳寿命估算。结果表明:在桥面板与纵肋连接处,桥面板疲劳裂纹寿命较短,而纵肋疲劳裂纹寿命较长,这与国内外现场实测及试验结果相吻合;在横梁与纵肋连接处,其主应力较大且应力集中效应明显,极易产生疲劳裂纹。

Estimation of Fatigue Life of Typical Fatigue Cracks of Orthotropic Steel Decks of Railway Bridges

Typical fatigue cracks observed in the orthotropic steel decks of railway bridges were investigated,and their analytical models were developed.The stress variations of the main weld connections,under railway loading,were simulated and analyzed using the finite element method.The least favorable locations of the typical fatigue cracks were determined on the basis of the stress analysis in conjunction of the global model and sub-structural fine models.Sub-structural models were developed using the plane strain or solid elements in the typical fatigue areas,and the influence of stress concentration sensitive to the detail of welded joints was analyzed.Based on the FE results,the stresses perpendicular to the cracks were analyzed along the crack growth direction,and the fatigue life of the typical cracks were estimated by numerical integration of the Paris law in terms of the liner elastic fracture mechanics.The results illustrate as follows: In the rib-to-deck joint the fatigue life of root and toe cracks through deck plates is much smaller than the longitudinal rib wall cracks,which is consistent with the results of field measurements and fatigue tests in lab;compared with the rib-to-deck joint,cracks are more likely to occur in the rib-to-diaphragm joint due to the relatively large principal stress and high stress concentration.