正交异性钢桥面板顶板贯穿型疲劳裂纹研究

Research on Fatigue Cracks through Deck-plate in Orthotropic Steel Deck

正交异性钢桥面板的顶板疲劳裂纹,特别是萌生于焊根的顶板裂纹,对桥面系的安全使用危害很大。钢桥面板有限元节段模型计算分析表明,顶板横向应力分布在横隔板截面和跨中部分差别较大,前者类似固端梁,后者类似弹性支承多跨连续梁;顶板-纵肋连接处的应力纵向和横向影响线很短,疲劳验算可不考虑同一车辆轴重间的相互影响及多车效应;横隔板截面处萌生于焊根的顶板裂纹更易发生。参数分析结果还表明,增加顶板厚度可大大降低顶板的应力幅,铺装层的完整性对钢桥面板十分重要。此外,通过对现有试验数据的分析,采用焊趾或焊根处顶板底面的横向热点应力作为参考应力,顶板裂纹的疲劳等级可达到Eurocode的125级。

Fatigue cracks through the deck-plate, especially initiated at the root of weld between rib and deck-plate, may be a great threat to the traffic safety of deck structure. Finite element analyses for section models of steel decks were performed. The analysis results show that （1） the transverse distribution of transverse stresses in the deck-plate behave differently at the sections of diaphragm and the field between diaphragms, the former resembles a clamping beam supported by the diaphragm, and the later behaves like a multi-span beam supported elastically by rib webs ; （2） the influence lines of stresses at the deck-to-rib joint are very short in both longitudinal and transverse directions, indicating that the interrelationships of multiple axles of a vehicle can be neglected ; （3） the root-deck fatigue cracks at the diaphragm are prone to appear compared to other deck fatigue cracks. The parametric analysis results show that increasing the thickness of deck-plate can reduce its stress range significantly and the wearing surfacing also play a vital role. Additionally, 125 of the fatigue classification in Eurocode was suggested with respect to the deck-plate fatigue cracks based on the specified extrapolated stress at the weld root/toe.