Displacement Induced Fatigue Damage on Steel Bridges and Its Retrofitting Method

1.提出了板梁桥分析模型的新方法。在该方法中，分析模型是通过以下方式构建的。大多数自由度被分配到结构细节的邻域，在那里局部应力被估计，而其他整个结构在宏观意义上被建模，花费相当少的存储空间。最大自由度的结构是通过参考相关研究并考虑静力学来确定的。为了实现所提出的模式，必须将板单元与梁单元连接。为了研究钢桥面纵肋和横肋连接的受力性能，在东京的两座大桥上进行了应力测试。根据测得的应力，利用反问题概念计算了纵筋和横筋的影响线。进行了有限元分析，明确了各种变形模式与波动…的关系更多的局部压力。在基于局部应力的疲劳评估中，如何定义应力来评估疲劳强度是非常重要的。在本研究中，对三种不同类型的试件进行了焊趾附近应力分布的测量和分析。通过这些结果和在这些试件上获得的疲劳试验数据，研究了确定局部应力来评估疲劳强度的方法。采用试验和有限元分析相结合的方法，对焊接构件扇贝细节的疲劳强度进行了研究。基于名义应力的这种细节的疲劳强度极低，这是因为在扇形的缝隙处出现了较高的应力集中。研究了从焊缝根部疲劳开裂失效的承载角焊十字接头的疲劳设计应力和许用应力范围。收集整理了大量已有的节点疲劳试验数据。此外，还利用有限元应力分析和能量法得到的应力强度因子对疲劳裂纹扩展进行了分析。较少

1. A new method of analysis model for plate girder bridges is proposed. In the method, analytical model is constructed in the following way. Most degrees of freedom are allocated to the neighborhood of the structural detail where local stresses are estimated and other whole structure is modeled in macro sense spending considerably few memory size. The structure where most degrees of freedom are to be allocated is decided by referring to related studies and considering statics. In order to realize a proposed mode, plate elements must be connected with beam elements.2. In order to investigate the behavior at the longitudinal and transverse ribs connections of steel deck plates, stress measurements were carried out on two bridges in Tokyo. From the measured stresses, the influence lines of the longitudial and the transverse ribs were calculated by using inverse problem concepts. F.E.M.analysis was carried out to make clear the relationship between various distortion modes and fluctuations … More of local stress.3. For the fatigue assessment based on the local stress, it is important thow to define the stress to assess the fatigue strength. In this study, the measurements and the analysis of the stress distributions near the welded toe are carried out on three different types of specimen. Through these results and he fatigue test data which has been obtained on these specimens, the method to define the local stress to assess the fatigue strength is investigated.4. Fatigue strength of scallop details in welded structural members were investigated by experiment and FEM analysis. Fatigue strength of this detail based on nominal stress was extremely low because of high stress concentration occurred in the gap of scallop.5. Fatigue design stress and allowable stress range of load-carrying fillet welded cruciform joints which fail by fatigue cracking from the weld root were investigated. Many existing fatigue test data of the joints are collected and rearranged. Furthermore, fatigue crack propagation analysis is also carried out by using stress intensity factor which is obtained from the finite element stress analysis and the energy method. Less