Diagnosis System of Fatigue Damage and Development of Retrofitting Technologies for Existing Steel Highway Bridges

本研究项目的概要如下。（1）在Internet上建立了疲劳与维修案例数据库。在数据库中，钢桥的疲劳损伤情况。按原因列出并组织。最后，通过实例说明了对受损结构的修复和加固方法的有效性。（2）针对平面外节点的疲劳损伤，提出了螺栓止动孔、打磨、低温相变焊缝材料补焊等新的加固方法，并通过大比例梁试件疲劳试验，对加固效果进行了定量评价。（3）在疲劳损伤预测方法研究方面，采用有限元分析和现场应力测试相结合的方法，对疲劳损伤的原因进行了详细的研究。其结果是，它是明确的，有意想不到的原因，如三维行为由于复杂的结构和振动特性。（4）开发了桥梁监测系统，掌握桥梁的现状。在监测系统中，设置在桥梁上的传感器测量的数据通过光纤网络实时传输到远程监测中心。在该监控系统中，动态称重（WIM）算法是内置的，以获得车辆的重量。通过WIM，发现了可能导致疲劳损坏的非法超重卡车。（5）对于焊接修复，必须从材料性能的角度检查层状撕裂的风险。在这项研究中，表明，应用焊接修复方法，钢的硫夹杂物必须小于0.01%。提出了判断焊接修复方法适用性的正确步骤。

The summary of this research project is as follows.(1)Database of fatigue and repair cases was built on the Internet. In the database, fatigue damage cases in steel bridges were. listed and organized by the causes. Furthermore, the repairing and retrofitting methods applied to the damaged structures were shown with the effectiveness of the methods.(2)For the new retrofitting methods for fatigue damage of out-plane gusset joints, bolted stop holes, grinding, additional welding by low temperature transformation weld materials were proposed and the effectiveness of them was evaluated quantitatively by fatigue tests with large scale girder specimens.(3)For the development of fatigue damage prediction methods, the causes of fatigue damage were investigated in details by Finite Element Analysis and field stress measurements. As a result, it was clarified that there are unexpected causes such as three dimensional behaviors due to complicated structures and vibration characteristics.(4)The monitoring systems of bridges were developed to grasp the present conditions of the bridges. In the monitoring system, the measured data by the sensors set on the bridges were transferred to the remote monitoring center on real-time through fiber-optic networks. In this monitoring system, the Weigh-in-Motion (WIM) algorism was built in to obtain vehicle weights. By the WIM, illegally overweight trucks that can cause fatigue damage were detected.(5)For the repairs by welding, the risk of lamellar tearing must be examined from the viewpoint of material properties. In this study, it was shown that to apply welding repairing methods, the Sulfur inclusion of the steels must be less than 0.01%. Furthermore, the proper procedure to judge the applicability of welding repairing methods was proposed.