中文摘要：

为探讨结构的失效机理，研究了结构中易损部位的损伤及其演化过程对结构局部和整体响应的非线性效应．对桥梁结构中典型的纵向加劲钢桁架的局部损伤破坏过程进行了模拟试验研究．通过在桁架的局部和整体分别设置力学响应的测试点，同步观测并分析了局部损伤区的应变分布以及桁架整体挠度的变化规律．研究结果表明：桁架易损部位的损伤演化导致局部应变与整体挠度响应产生了非线性效应；桁架焊接区域内的材料发生严重塑性损伤，大大加剧了局部应变分布的奇异性；在各级别损伤程度下，局部应变和整体挠度响应都与易损部位的损伤表现出弱非线性相关．而应变响应的非线性效应远比挠唐响应明显．

英文摘要：

Nonlinear effects of local and global structural responses caused by damage evolution in the vulnerable zone of structures are studied to explore the failure mechanism. Simulation tests for the failure process are carried out using a welded steel truss which is a reduced scale sample of thelongitudinal stiffening truss typically used in long-span bridges. The mechanical responses, such as law of strain distribution at the damage zone and deflection of the whole structure; are synchronously measured and analyzed during the loading process. The results show that all the nonlinear effects oflocal strain and global deflection responses are originated from damage evolution. Materials in dam- age zone present serious plastic damage and the singularity of strain distribution becomes worse. For each damage degree, both strain and deflection responses present nonlinear correlation with the val- ues of damage, while nonlinear effect of local response is much more appreciable than that of globalresponse.