城市轨道地下结构在环境、人为、材料老化等多因素下会产生不同程度的损伤，影响结构的正常服役性能，因此对城市地下结构进行健康监测和损伤识别尤为重要。地下结构特点是沿纵向方向较长，隧道-土体系统的有限元模型单元和结点多，若对整体隧道精确的有限元模型进行基于模态特性灵敏度分析的损伤识别，往往效率很低，甚至难以收敛。为了解决大型复杂地下结构的损伤诊断，采用基于等效刚度原理的模型等效简化，将复杂隧道-土体体系简化成等效截面的环形梁，分析隧道结构纵向方向的模态特性，并利用基于灵敏度分析的模型修正方法对隧道衬砌在裂缝、剥落和强度降低三种损伤情况下进行损伤识别。%The degradation of the materials and the complexity of the environment for the underground structure will cause the damages, which affect the service performance of the underground structure. Therefore, it is vital for the underground structure to employ the structural damage identification and health monitoring. Because of the super-long characteristics of the tunnel in the longitudinal direction and the huge number of the element and nodes for the tunnel-soil model, the efficiency and accuracy of the damage identification based on modal sensitivity analysis are quite low for the accurate tunnel-soil finite element model. In order to diagnose the damage condition of the large and complex underground structure, the simplified model is adopted by the equivalent stiffness principle, which means the complex tunnel-soil system is simplified as the annular beam with the equivalent cross section. Furthermore, the modal characteristics of the underground structure in the longitudinal direction are analyzed. Combing with the sensitivity-based model updating method, the damage location and extent of the tunnel are identified in the case of the concrete cracks, concrete spalling and strength degradation.
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