A Study On Statistical Modal Identification Based Method For Structural Damage Identification

Structural Modal Identification use excitation force data and measured data of the system to estimate the unknown modal parameters.But it is hard to set a manual excitation force in practical engineering.And manual setting some parameters during identification makes results subjectively.To avoid these problems,this paper applies data mining technology.A modified Random Decrement Technique(RDT)based on identification-probability histogram(IpHist)method and modal contribution is proposed in this paper to achieve the auto-made structural modal identification.Then,the concept of real modal parameters batch is proposed to establish the structural damage progressive recognition algorithm based on dynamic characteristics,which can obtain high-precision damage identified results.The work presented in this dissertation contains the following aspects:Firstly,in view of the singular value problem of acceleration random decrement signature for the traditional RDT,a corresponding signature truncation method is proposed to improve the modal identification effect.Then,for the extraction problem of structural real mode shapes in the practice of modal identification,a minimum distance method is applicable with high noise resistance for extracting real mode shapes under all kinds of responses.Secondly,an improved random decrement technique based on identification probability histogram is proposed to deal with the manual setting problem of triggering condition and reference channel.K-means-CP clustering algorithm is used to consistently cluster the modal parameters identified under different trigger conditions and reference channels.The spurious modals are firstly culled according to the identification-probability.Then,based on the concept of modal contribution,two types of indexes are proposed.Critical value of modal contribution indexes is setted to complete the secondary culling,which means an auto-made structural modal identification without spurious modals.Thirdly,according to the real modal results with identification-probability,real modal parameters batch is reconstructed.Based on the Bayesian estimation principle,the recognition progressive algorithm of structural damage factor is established,to obtain the damage factor statistics from real modal parameters batch.The application effect of the substructure correction index and the flexibility index is compared.The substructure correction index is with high computational efficiency but poor stability.The flexibility index is more applicable.