焊接残余应力对正交异性钢桥面板疲劳性能影响研究

Orthotropic steel bridge decks have been extensively used in bridge deck structure for modern steel bridges, while whose fatigue problems become increasingly serious due to the complexities of structural configurations and weld spatial organizations. Besides to the external loading characteristics, the structure detail and the welding residual stress are two main factors that affect the fatigue performances of orthotropic steel bridge decks. For the former, a large number of studies have been conducted both at home and abroad, and some of the achievements have been included into the specifications or standards of various countries. However, there are comparatively few researches on the magnitude and distribution of the welding residual stress, and its influence on the fatigue performances in the orthotropic steel bridge decks. Therefore, it is quite necessary to carry out a systematic and comprehensive research on this topic. This project is intended to determinate the magnitude and distribution of welding residual stresses by means of numerical simulation and residual stress measurement, to clarify the coupling mechanism of welding residual stress and fatigue crack growth based on fracture mechanics and fatigue crack growth rate test, and to reveal the influence mechanism of welding residual stress on the fatigue performance of orthotropic steel bridge decks through the simulation of fatigue crack propagation and the controlled fatigue tests with and without welding residual stress. The expected results of this project are beneficial to improve the fatigue life of bridge steel structures, are helpful for the revision and improvement of the bridge steel structure design codes, and can provide the technical support for the establishment of bridge welding code in our country.

正交异性钢桥面板已广泛应用于现代钢桥的桥面结构中，但其构造复杂、焊缝交错，在车辆轮载的反复作用下，疲劳问题日益突出。除外荷载特性外，影响其疲劳性能的因素主要是构造细节与焊接残余应力。对于前者，国内外已经进行了大量的研究，部分成果已纳入各国规范，而就焊接残余应力的大小与分布及其对正交异性钢桥面板疲劳性能的影响研究较少，因此对该问题进行系统深入的研究是十分必要的。本项目拟采用数值模拟与残余应力测试，获知正交异性钢桥面板焊接残余应力大小与分布；基于断裂力学与疲劳裂纹扩展速率试验，厘清焊接残余应力与疲劳裂纹扩展的耦合作用机制；基于疲劳裂纹扩展的模拟与有、无焊接残余应力的对照疲劳试验，揭示焊接残余应力对正交异性钢桥面板疲劳性能的影响机理。项目预期研究成果有利于提高正交异性钢桥面板的疲劳性能，有利于我国桥梁钢结构设计规范的修订与完善，并对我国《桥梁焊接规范》的制订提供一定的技术支撑。

正交异性钢桥面板疲劳问题日益突出，焊接残余应力是疲劳性能的主要影响因素。项目就此开展研究，主要内容与结果有：①基于优化设计方法，提出了求解热源模型参数的方法，该方法能够高精度地求解焊接热源模型参数；②针对盲孔法残余应力测试，借助有限单元法提出了一种适应于高值残余应力测试的求解方法，该方法拓宽了钻孔应变释放法的适用范围；③为剔除钻孔应变释放法残余应力测试中的钻孔偏心误差，研发了五栅式应变花产品、创建了配套算法、并基于ANSYS编制了残余应力求解程序，该程序能适用于高达屈服强度的残余应力求解，即使当钻孔偏心达到0.1倍应变栅中心圆直径时仍具有较高的求解精度；④结合计算机图形学及等参单元逆变换算法提出了残余应力映射技术，并以平板对接焊为例加以验证，结果表明该技术能有效地进行模型间应力的映射；⑤基于线弹性断裂力学，借助ANSYS平台，建立了考虑焊接残余应力的三维疲劳裂纹扩展模拟技术并编制了模拟程序，该程序在一定程度上突破国外的技术限制，能在疲劳裂纹扩展模拟中考虑残余应力的影响并具有较高的预测精度；⑥采用数值模拟及疲劳裂纹扩展速率试验，揭示了焊接残余应力对疲劳裂纹扩展的耦合作用机制；⑦基于热弹塑性有限元法结合残余应力测试，获知了正交异性钢桥面板焊接残余应力的大小与分布，并借助建立的裂纹扩展模拟技术结合疲劳试验，揭示了焊接残余应力对正交异性钢桥面板疲劳性能的影响机理。⑧ 研究了自然环境下不同暴露时间的Q235钢试件的蚀坑形貌及力学性能，获得了蚀坑形貌特征演变规律，揭示了蚀坑形貌对材料力学性能的影响机理。研究成果为焊接构造设计、疲劳裂纹加固及焊接残余应力的预测与控制提供了理论基础，具有广泛的应用前景。