Research On Seismic Damage Diagnosis Method Of Arch Dam Based On Modal Recognition

In order to make use of seismic observation for arch dam damage diagnosis,especially after earthquake,the calculation method of damage diagnosis index should be studied first.Among all kinds of methods to study structural vibration characteristics,modal parameter identification is the most widely used method at present.It is the basic idea of damage diagnosis method to evaluate the state of arch dam according to the modal index obtained from identification and calculation.Based on the seismic observation data of arch Dams,a comparative study is made on the modal parameter identification methods.Combined with the numerical simulation method,the sensitivity of typical modal indexes is analyzed and studied,which provides a basis for damage diagnosis of arch Dams by modal indexes in the future.The specific research content is mainly divided into the following three parts:(1)According to the latest development trend of structural dynamics research,the modal parameters of arch Dams are identified by different seismic observation records and different modal identification methods.In order to verify the rationality of the results,we also refer to the analysis results of other scholars.Finally,we make a comparative study of these identification results,analyze the causes of the differences,and evaluate their advantages and disadvantages.(2)The commonly used modal parameters for structural damage diagnosis include three basic modal parameters,natural frequency,damping and mode shape,and the derived modal parameters.These modal indices have definite physical significance and can characterize the damage state of the whole structure.Some indexes also have the function of damage localization.Based on the modal parameter identification and numerical simulation technology,the sensitivity of typical modal indexes is analyzed and compared,which provides a basis for the application of modal indexes in the damage diagnosis of hydraulic arch Dams.(3)The method based on modal index identification mainly compares the vibration information measured in the field with the initial model information,analyzes the change of model stiffness by studying the change of modal parameters of the structure,and then identifies model before and after the damage,so as to judge the change of the parameters of the structure,so as to diagnose the structural damage.