开口纵肋钢桥面板疲劳裂纹扩展特性研究

RESEARCH ON PROPAGATION CHARACTERISTICS OF FATIGUE CRACK FOR STEEL BRIDGE DECKS WITH OPEN-SHAPED LONGITUDINAL RIBS

为研究开口纵肋钢桥面板的疲劳裂纹扩展特性,依托云南楚大高速公路项目,以钢桥面板疲劳开裂问题最为突出的纵肋与顶板焊接细节和纵肋与横隔板交叉构造细节为研究对象,对开口纵肋钢桥面板的疲劳裂纹扩展特性及优化设计进行研究。研究结果表明:在疲劳裂纹扩展初期四种典型疲劳开裂模式的裂纹扩展速率均随着裂纹深度的增加而不断增大,当裂纹深度达到4 mm后,开裂模式C1、C2和C3的疲劳裂纹扩展速率达到其峰值,开裂模式C4的裂纹扩展速率在整个过程都随着裂纹深度的增加而不断增大;开口纵肋钢桥面板的疲劳寿命由开裂模式C1和C4控制;增加顶板厚度和铺设混凝土现浇层均可显著降低开口纵肋钢桥面板的等效应力强度因子幅值,但是铺设混凝土现浇层对于钢桥面板疲劳性能的影响更加显著;建议通过铺设混凝土现浇层的方式提升钢桥面板的疲劳性能。

In order to research propagation characteristics of fatigue crack for steel bridge decks with open-shaped longitudinal-ribs, the rib-to-deck welded joint and rib-to-diaphragm welded joint were considered as research objects, based on the Yunnan Chuda Expressway Project. The fatigue crack propagation characteristics and optimal design of steel bridge decks with open-shaped longitndinal ribs were systematically studied. The results indicated that the four typical fatigue cracking modes all increased with the increase of crack depth, in the early stage of fatigue crack propagation. When the crack depth reached 4 mm, the fatigue crack growth rates of cracking modes C1, C2 and C3 reached their peaks, and the crack growth rate of the cracking mode C4 increased continuously with the increase of the crack depth throughout the process. The fatigue life of the steel bridge deck with open-shaped longitudinal ribs was controlled by the cracking mode C1 and C4. Increasing the thickness of the deck and laying a concrete cast-in-situ layer could significantly reduce the equivalent stress intensity factor amplitude of the steel bridge deck, but the laying of the cast-in-situ concrete layer had a more significant impact on the fatigue performance of the steel bridge deck. It was recommended to improve the fatigue performance of steel bridge decks by laying cast-in-situ concrete layers.