基于模态柔度理论的结构损伤诊断试验研究

利用多参考点脉冲锤击法的输入输出动力信号获取结构的模态柔度,可以对结构进行损伤识别,设计了一根钢筋混凝土简支梁和一块钢-混凝土组合板的静动力试验.对不同损伤状态下的简支梁和组合板进行了动力测试,得到其模态柔度矩阵,并用来预测结构在荷载作用下的位移.简支梁试验结果表明,随着损伤程度的加深,结构自振频率降低,阻尼比增大,柔度增大,但自振频率只能判断结构损伤的出现,模态柔度则能够综合全面地反映钢筋混凝土简支梁结构的损伤位置和损伤程度.组合板试验表明,在线弹性状态下,动力测试与静力测试获得的模态柔度矩阵相差很小.设计了支座刚度变化、连接件损伤和横向支撑破坏这3种损伤工况,并用这3种工况来模拟实际桥梁结构可能出现的损伤状况.通过对比结构损伤前后的模态柔度位移信息,成功实现了组合板的损伤识别.

Experimental Research on Structural Damage Detection Based on Modal Flexibility Theory

The utilization of the input and output dynamic signals from multiple reference hammer impact method (MRIT) for modal flexibility extraction and structural damage identification was studied. Static and dynamic experiments on a Reinforced Concrete (RC) simply supported beam and a steel-concrete composite bridge deck were designed. MRIT was conducted on the simply supported beam and composite plate under different damage states, and modal flexibility was obtained in the test, which can be used to predict the displacement under applied loading. The beam test results demonstrated that the natural frequency decreased while the damping ratio and flexibility increased with the development of damage. Changes of natural frequency can only determine the existence of structural damage, while the changes of modal flexibility can indicate the damage location and damage degree of RC beam. Steel-concrete composite slab test results demonstrated that the differences between dynamic flexibility and static flexibility match well under the linear elastic state. Three damage cases were designed to simulate the damage situation on real bridges, which are the removal of cross diaphragm, changes of boundary condition and damage of connectors. By comparing modal flexibility information before and after structural damage, the damage of steel-concrete composite slab was achieved.