中文摘要：

大型土木结构的失效劣化过程是一个跨尺度损伤演化过程，在相同的时间节点不同的空间尺度下，通常表现出独特的损伤演化响应特征和力学特性。该文以某大型桥梁纵向加劲钢桁架的缩尺模型为研究对象开展疲劳损伤演化过程多尺度同步观测试验工作，综合运用电测技术、光测技术和动态测试技术实时监测桁架疲劳损伤演化过程，据此分析对比桁架在细观和宏观尺度下的损伤演化响应特征和力学特性。在电测技术观测到桁架局部疲劳裂纹萌生之后，光测和动态测试技术得以继续追踪疲劳裂纹的扩展过程并评价局部损伤演化对构件以及结构整体力学特性的影响，结果表明：结构局部细观尺度上的损伤演化不至于影响结构宏观尺度的整体力学特性，但是局部损伤的累积必将导致结构失效劣化。

英文摘要：

This paper aims to synchronously explore the fatigue damage evolution process m meso- aau n,mu- scales by experimental studying on a welded truss structural specimen as the scaled model of the longitudinal stiffening truss in long-span bridges. Several testing techniques are used to measure and analyze the damage evolution process so that mechanical properties and characteristic response are respectively compared in different scales. While hot-spot dynamic strains and extension of a plastic zone on the toe of the weld of the tested specimen are recorded by strain measurement technique, the fatigue cracking process is measured by optical technique and the variation of structural dynamic parameters due to the fatigue cracking is finally measured and identified according to dynamic testing technique. The results show that the fatigue damage evolution in meso-scale has few influences on the variation of mechanical properties in maro-scale, but the long-time evolution of damage accumulations in a local structure will certainly lead to the deterioration and failure of a global structure.