Rehabilitation of existing steel bridges by field treatment of welds

由于现有民用基础设施的恶化而产生的社会成本的很大一部分可以归因于钢桥的疲劳和腐蚀。在世界许多地方，由于交通量和车辆重量的增加，钢桥因疲劳而加速老化。焊后处理方法旨在改善疲劳性能，已在其他行业使用了一段时间。这些方法通常通过修改焊缝轮廓和去除裂纹状缺陷或通过改变处理后焊缝表面附近的残余应力来增加疲劳寿命。尽管它们的有益效果被广泛认可，但存在对焊后处理方法的可靠性的担忧，特别是在使用中（变幅）载荷条件下。最近的研究审查并解决了其中的一些问题。基于这项工作，本文提出的研究的主要目标是执行一些仍然需要的重要步骤，将现场焊后处理转化为现有钢桥可行的修复替代方案。主要研究目标的实现将取决于分析模型的开发，该模型可以可靠地预测现场焊后处理的效益，变幅加载条件。这种模型的开发将需要一个多方面的方法，包括各种可能的处理效果的实验室测量和疲劳试验模拟焊后处理在现场的部分方式通过使用寿命。经验证的分析模型将用于进行概率评估研究，以确定整个桥梁结构的处理效益。预计主要研究目标的实现将导致与钢桥相关的生命周期成本的显着降低。此外，通过拟议的研究，一批硕士和博士。候选人将在未来几年内受到政府和负责加拿大基础设施维护的私人机构的高度追捧的领域接受培训。

A significant percentage of the cost incurred by society due to the deterioration of existing civil infrastructure can be attributed to the fatigue and corrosion of steel bridges. In many parts of the world, the deterioration of steel bridges due to fatigue is accelerated by increasing traffic volumes and vehicle weights.Post-weld treatment methods, aimed at improving fatigue performance, have been used for some time by other industries. These methods generally increase fatigue life either by modifying the weld profile and removing crack-like defects or by altering the residual stresses near the surface of the treated weld.Although their beneficial effects are widely acknowledged, concerns exist about the reliability of post-weld treatment methods, in particular under in-service (variable amplitude) loading conditions. Recent research has examined and addressed a number of these concerns. Based on this work, the main objective of the research proposed herein is to perform a number of the important steps still needed to transform post-weld treatment in the field into a viable rehabilitation alternative for existing steel bridges.Achievement of the main research objective will hinge on the development of analytical models that can reliably predict the benefit of post-weld treatment in the field under realistic, variable amplitude loading conditions. The development of such models will require a multi-faceted approach including laboratory measurements of the various possible treatment effects and fatigue tests simulating post-weld treatment in the field part way through the service life. The validated analytical models will be used to perform probabilistic assessment studies to determine the benefit of treatment for entire bridge structures.It is expected that the achievement of the main research objective will lead to significant reductions in the life-cycle costs associated with steel bridges. In addition, through the proposed research, a number of M.Sc. and Ph.D. candidates will receive training in fields expected to be highly sought after in the coming years by the government and private agencies responsible for the maintenance of infrastructure in Canada.