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为研究正交异性钢桥面板钢箱梁结构纵肋现场接头的疲劳性能,以港珠澳大桥中2类典型闭口截面U形纵肋的现场接头(焊接与栓接)作为研究对象,对其疲劳特性进行了试验和理论研究。依据实桥结构尺寸设计了2组4个足尺试件模型,并对现场焊接与栓接2种常用接头形式在设计寿命服役期内的疲劳性能进行了试验验证,在此基础上,对既有正交异性钢桥面板疲劳损伤案例中占比例较高的焊接接头疲劳损伤特性进行了相关疲劳试验与疲劳性能评估;通过在焊缝两侧对称布置2排电阻应变计获得不同疲劳加载次数下各测点的主拉应力实测值,揭示了焊接接头局部区域主拉应力随疲劳加载次数的变化规律,并结合超声波与磁粉探伤判断焊缝位置裂纹的萌生状况;分别建立实体与板壳有限元模型,计算出用于焊接接头疲劳评估的等效结构应力幅,探讨了结构应力法应用于该类细节疲劳评估的可行性和合理性。研究结果表明:2类纵肋现场接头中各关键测点的主拉应力在疲劳验证试验阶段基本保持不变,其疲劳性能均满足设计要求且具有一定的安全储备;随疲劳加载次数的增加,疲劳裂纹萌生初期的累积损伤会引起附近局部区域结构刚度下降,导致该区域内的主拉应力值出现不同幅度的增大;结构应力法适用于正交异性钢桥面板纵肋现场焊接接头部位的疲劳性能评估,且评估结果稳定、离散性较小。
In order to study the fatigue behavior of on-site joint of longitudinal rib of steel box girder with orthotropic steel deck, two kinds of typical joints with U-shaped longitudinal ribs (welding and bolting) of Hong Kong-Zhuhai-Macao Bridge are studied. Fatigue characteristics of the experimental and theoretical research. Two groups of four full-scale specimens were designed according to the size of the actual bridge. The fatigue performance of two commonly used joints in the field of welding and bolting during service life of design life was tested. On this basis, The fatigue damage characteristics of welded joints with higher proportion of the fatigue damage cases of orthotropic steel bridge deck panels were evaluated by fatigue tests and fatigue tests. Two different rows of strain gauges were placed symmetrically on both sides of the weld seam to obtain different fatigue loading times The measured values of main tensile stress at each measuring point reveal the variation law of the main tensile stress with the fatigue loading times in the local area of the welded joint, and determine the initiation of cracks at the weld by combining the ultrasonic and magnetic particle inspection. The physical and plate shell finite element Model, calculate the equivalent structural stress amplitude for the fatigue assessment of welded joints, and discuss the feasibility and rationality of the structural stress method applied to the fatigue assessment of such details. The results show that the main tensile stress of the key measuring points in the two types of longitudinal rib joints remain basically unchanged during the fatigue test phase and their fatigue performance meets the design requirements and has a certain safety margin. With the increase of fatigue loading times, The cumulative damage in the initial stage of fatigue crack initiation will cause the structural rigidity of the local area nearby to decrease, resulting in the different increase of the main tensile stress in this area. The structural stress method is suitable for the site of vertical welded joints in the longitudinal rib of orthotropic steel bridge deck Fatigue performance evaluation, and the evaluation results are stable, less discrete.