正交异性钢桥面板典型疲劳细节变形与裂纹尖端应力分析

为了解车轮荷载作用对正交异性钢桥面板典型疲劳细节的影响,以长门特大桥为背景,采用有限元法建立正交异性钢桥面板节段模型及易开裂部位的子模型,分析在不同横向荷载分布下3处典型疲劳细节受力及面内外变形,得到各细节最不利加载位置。对最不利位置进行加载,分析疲劳裂纹尖端应力强度因子变化规律,研究不同疲劳细节裂纹类型及扩展能力。结果表明:单轮荷载作用下,横隔板弧形缺口位置会发生面内外变形,顶板-U肋焊根处以面外变形为主,横隔板间的顶板-U肋焊缝焊根位置面外变形最大。在裂纹较短时,随着长度的增加,弧形缺口裂纹从张开型裂纹逐渐转向张开型、滑开型混合裂纹,且横隔板处的顶板-U肋焊根裂纹为复合型裂纹,横隔板间的顶板-U肋焊根裂纹为张开型裂纹。横隔板弧形缺口裂纹和顶板-U肋焊缝焊根裂纹的尖端应力强度因子的最大值,分别出现在裂纹长度为20 mm和40 mm附近,该处裂纹较容易继续扩展。

Analysis of Deformation of Typical Fatigue Details and Stresses at Tip of Cracks in Orthotropic Steel Deck

To investigate the influence of wheel loads on typical fatigue details of orthotropic steel deck,the Changmen Bridge was taken as the study background.The finite element method was used to build the sectional model of the orthotropic steel deck and the sub-models of the locations prone to crack.The mechanical properties and out-of-plane deformation of three typical fatigue details under different distribution patterns of transverse loads were analyzed,and the most adverse loading locations in each detail was obtained,to which loads were applied.Based on those,the changing law of intensity factors of stresses at the tips of fatigue cracks was analyzed and crack patterns and propagation performance of different fatigue details were studied.The results show that under the action of single-axle load,in-plane and out-of-plane deformations will occur at the arch gaps in the diaphragms,the out-of-plane deformation plays a dominant role at the welding toes of the U ribs,and the out-of-plane deformation at the root of welding joints of the top plates between diaphragms and the U ribs.When the cracks are short,the cracks at the arch gaps gradually transform from splitting cracks to the mixed pattern of splitting and slipping cracks,and the cracks in the roots of welding joints of the top plates at the diaphragms and the U ribs are mixed-mode cracks and the cracks in the roots of welding joints of the top plates between the diaphragms and U ribs are the splitting cracks.The maximum intensity factors of stresses in the arch gap of the diaphragms and at the tips of the cracks in the roots of the welding joints of top plates and U ribs occurred near the cracks with length of 20 mm and 40 mm,respectively,and at these locations,cracks are prone to propogate progressively.