在役钢桥面板纵肋与顶板焊根疲劳裂纹内焊加固方法

Internal welding reinforcement method for fatigue crack at weld root on rib-to-deck of in-service steel bridge deck

为实现纵肋与顶板焊根疲劳裂纹的有效加固,提出了能够满足在役钢桥面板加固需求的内焊加固方法,研发了自动化焊接机器人和相关关键装备;设计了4个试验模型对方法和装备的有效性和适用性进行研究,验证了纵肋与顶板焊根产生疲劳裂纹的开裂模式;使用所研发的专用焊接设备在纵肋内部进行焊接加固,进行了加固结构的疲劳破坏试验;对比了试验结果与有限元模拟结果,分析了加固后结构的疲劳性能,验证了内焊加固方法的有效性。研究结果表明:内焊加固方法能够将既有的焊根裂纹转化为内部缺陷,研发的装备能够实现原位加固,有效抑制疲劳裂纹的扩展,使已开裂焊接细节的疲劳寿命提高了66%~157%;由于各开裂模式具有不同程度疲劳损伤累积,加固后焊接细节会发生主导开裂模式迁移;对于包含多开裂模式的焊接细节,加固后的剩余疲劳寿命与各开裂模式的实际疲劳损伤累积程度以及加固方法对各开裂模式受力特性的扰动程度两方面的因素密切相关。

To achieve effective reinforcement of fatigue crack at weld root on rib-to-deck,an internal welding reinforcement method was proposed to meet the requirements of in-service steel bridge decks,and automated welding robots and associated key equipment were developed.Four test models were designed to study the effectiveness and applicability of the method and equipment.The cracking mode of fatigue crack at weld root on rib-to-deck was validated.The developed specialized welding equipment for internal welding reinforcement was used internally within the rib,and fatigue failure tests on the reinforced structure were conducted.The results of experiment and finite element simulation were compared.The fatigue performance of the structure after reinforcement twas analyzed,and the effectiveness of internal welding reinforcement methodd was confirmed.Research results indicate that the internal welding reinforcement method can transform the existing weld root cracks into internal defects.The developed equipment enables in-site reinforcement,effectively suppressing the expansion of fatigue cracks,and enhancing the fatigue lives of the cracked welded joints by 66%-157%.Due to the different degrees of fatigue damage accumulation in various cracking modes,a transition in the dominant cracking mode of the welded joints occurs after reinforcement.For welded joints containing multiple cracking modes,the remaining fatigue life after reinforcement is closely related to the actual fatigue damage accumulation levels of each cracking mode and the degree of disturbance of reinforcement methods on the stress characteristics of each cracking mode.5 tabs,18 figs,36 refs.