港珠澳大桥正交异性钢桥面板纵肋现场接头疲劳特性

Fatigue Properties on Field Splice Joints of Longitudinal Ribs in Orthotropic Steel Bridge Decks of Hong Kong-Zhuhai-Macao Bridge

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。

To investigate the fatigue properties on field splice joints of longitudinal ribs of orthotropic steel decks（OSDs）,two types of typical field splice joints（welded and bolted joints）of U-ribs with closed section in Hong Kong-Zhuhai-Macao Bridge were taken as the research object and the fatigue test and theoretical analysis were carried out to explore their fatigue properties.According to the dimension of real bridge,four full-scale fatigue test specimens,which were divided into two groups,were designed to verify the fatigue performance of these twojoints during the design service lifetime.On this basis,related fatigue test and fatigue evaluation were conducted to investigate the fatigue damage characteristics of welded joints with higher fatigue and damage ratio among existing OSDs;two rows of resistance strain gauges were symmetrically arranged in two sides of weld to obtain the measured principal tensile stress of measuring points under different fatigue loading cycles,the variation of principal tensile stress of local region of the welded joint with fatigue loading cycles was revealed and the conditions of the fatigue crack initiation around the weld can be reasonably estimated by combining with the results of ultrasonic and magnetic powder inspections;the solid and shell finite element models were established to calculate the equivalent structural stress amplitude applied to evaluate fatigue performance of welded joints,the feasibility and rationality of structural stress method on the detail fatigue evaluation were further explored and discussed.The results show that the principal tensile stresses of key measuring points among two types of joints remain the same basically,their fatigue properties satisfy the requirements of design and have certain safety margin;the damage accumulation during the early fatigue crack initiation can cause stiffness degradation of local areas nearby and increase the values of principal tensile stress of local measuring points on different levels as fatigue loading cycles increase;the structural stress method is appropriate for fatigue performance evaluation of the field welded joints,and the assessment results have high stability and small dispersion.