| Structural health monitoring is significant to prevent disaster accidents of engineering structures,and guarantee the security,integrity and durability of structures.The damage detection methods based on the structure vibration is one of the core technologies of structural health monitoring system.The principle is detecting structural damage through analyzing the change of structural modal parameter and dynamic response.For the damage identification of complex large-scale structure,when conduct it for dynamic test,there is a need for a large number of sensors to install and a large amount of data to process accordingly,which is not conductive to accurate and efficient damage identification.Aimed at these problems,this paper combine with the technique of substructure analysis based on power spectral density sensitivity analysis of dynamic responses,carry on the damage identification to key substructure which may exists damages,which verifies the effectiveness and feasibility of the method.The paper derives the algorithm of the damage identification by using the response power spectral density sensitivity analysis,and introduces dynamic substructural method and the freedom reduction technology.The specific studies and conclusions are as follows:Firstly,based on the formula of structure’s stochastic response in time domain,the formula for response power spectral density in frequency domain is deduced.In the process of structural damage identification,the sensitivity of structural modal parameters to structural physical parameters is obtained,and the finite-difference method is used to approximately replace the derivatives to avoid complex partial differential calculation.Secondly,for many situations,it can be knowed about the approximate location of structural damage.This paper introduces the substructure method of dynamic analysis to improve the efficiency of structural damage detection.By this method,the identification to whole structure can be transformed to local structure.At the same time,this paper provides a few methods of reducing structural freedoms to the problem of too many degrees of freedom of large complicated structures,and the errors size of these methods are analyzed and compared.Thirdly,combine the sensitivity analysis method of power spectrum with method of dividing and polycondensating substructures and apply into the structure damage identification.That is,divide the whole structure into substructures and reduce degrees of freedom,then form new mass matrices and stiffness matrices which were condensed.Based on that,the sensitivity analysis of power spectrum is performed to indetificate the structure damage.At the same time,the method is applied to damage identification of two frame models,which verify the feasibility and efficiency of the algorithm.Fourthly,establish a laboratory model according to the numerical model of the six-layer frame to carry out modal experimental research.Utilize the proposed method of this thesis to identify structural damages,then compare to the numerical results.Thus the validity of the method can be verified. |
