摘要
针对钢箱梁桥顶板U肋嵌补段对接焊缝的构造特点与受力状态,以润扬大桥钢箱梁为研究对象,基于线弹性断裂力学和长期监测数据,提出了该焊缝的疲劳可靠度分析方法.基于有限厚板半椭圆表面裂纹模型推导了焊缝的临界损伤累积函数,采用随机模拟的方法建立了临界损伤累积函数的概率模型.针对焊缝疲劳荷载效应的多峰分布特征,采用高斯混合分布建立了等效应力范围的概率模型.研究表明,顶板U肋嵌补段对接焊缝的临界损伤累积函数服从对数正态分布;焊缝等效应力范围的概率模型可表述为多个高斯分量的加权平均;润扬斜拉桥焊缝的疲劳可靠度显著大于相同位置的润扬悬索桥焊缝,反映了两桥钢箱梁局部构造的差异.该方法可为同类型桥梁的疲劳可靠度分析提供参考.
Aiming at the structural features and stress state of butt-welds in the embedded sections of U ribs in steel box girders,the Runyang Bridge was taken as an object to present fatigue reliability analysis method based on linear elastic fracture mechanics and long-term monitoring data. The critical damage cumulative functions were derived using the semi-elliptical surface crack model of finite thick plate. Then,a random simulation was adopted to obtain the probabilistic distributions of the critical damage cumulative functions. The Gaussian mixture distributions,which can address the multi-peak distribution of monitored data of fatigue loading effects,were used to establish the distribution models of equivalent stress ranges. It is found that the critical damage cumulative functions of the butt welds in the embedded sections of the U ribs follow a lognormal distribution. The probabilistic models of equivalent stress range can be described as the weighted average of several Gaussian components.At the same location,the weld reliability of the Runyang Cable-stayed Bridge is remarkably higher than that of the Runyang Suspension Bridge. This is due to the difference in local structure between the two bridges. The presented method can provide a reference for the fatigue reliability analysis of the same type bridges.
引文
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