基于等效结构应力法的正交异性钢桥面板体系疲劳抗力评估

正交异性钢桥面板的疲劳问题属于多疲劳失效模式下的结构体系疲劳问题，为研究其结构体系的疲劳失效模式和疲劳抗力，以典型的正交异性钢桥面板为研究对象，提出基于主导疲劳失效模式的结构体系疲劳抗力评估方法。由正交异性钢桥面板的重要疲劳失效模式入手，设计3组共8个足尺节段模型，通过疲劳试验研究确定纵肋与顶板焊接细节和纵肋与横隔板交叉构造细节的重要疲劳失效模式及其实际疲劳抗力；基于所提出的结构体系疲劳抗力评估方法，探讨引入镦边纵肋和双面焊等新型构造细节条件下正交异性钢桥面板结构体系的疲劳抗力问题。研究结果表明：纵肋与顶板焊接细节主导疲劳失效模式为疲劳裂纹萌生于焊根并沿顶板厚度方向扩展，而纵肋与横隔板交叉构造细节主导疲劳失效模式为疲劳裂纹萌生于端部焊趾并沿纵肋腹板扩展；初始制造缺陷会显著降低正交异性钢桥面板重要疲劳失效模式的疲劳抗力并导致疲劳失效模式迁移；对于正交异性钢桥面板的结构体系而言，引入新型镦边纵肋与顶板焊接细节无法提高结构体系的疲劳抗力；而引入纵肋与顶板新型双面焊细节，可使结构体系的主导疲劳失效模式迁移至顶板焊趾或纵肋与横隔板交叉构造细节，结构体系的疲劳抗力得到显著提高。

Fatigue Resistance Evaluation for Structural System of Orthotropic Steel Bridge Deck Based on Equivalent Structural Stress

The fatigue problem of orthotropic steel bridge decks (OSDs) is a fatigue problem of a structural system with multiple fatigue failure patterns. To study the fatigue failure patterns and fatigue resistance for structural systems of OSDs, an evaluation method for fatigue resistance of the structural system was proposed by determining the dominant fatigue failure pattern. Based on the important fatigue failure patterns of OSDs, a total of eight full-scale specimens were designed and tested to determine the important fatigue failure patterns and fatigue resistances of rib-to-deck welded joints and longitudinal rib-to-diaphragm welded joints. The effects of upsetting edge rib and double-sided weld of rib-to-deck welded joints on the fatigue resistances of OSDs were discussed along with evaluation method of the structural system. The results indicate that the dominant fatigue failure pattern of the rib-to-deck welded joints of normal and upsetting edge ribs are root-to-deck cracks; the dominant fatigue failure pattern of the rib-to-diaphragm welded joints is the fatigue crack initiated from the toe and propagated along the longitudinal rib. The fatigue resistances of important failure patterns are reduced owing to the initial manufacturing defects, and the dominant fatigue failure patterns are thus transferred. For the dominant fatigue failure pattern of an OSD, the fatigue resistance of a structural system cannot be significantly improved by introducing the upsetting edge rib. The dominant fatigue failure pattern of an OSD will thus be transferred to the toe-to-deck or longitudinal rib-to-diaphragm welded joints through the double-sided welds, and the fatigue resistance of the OSD improves.