An Identification Method Of Structural Damage Based On Frequency Response Functions

Structural damage identification method is an important part of the structural health monitoring.At present,the structural damage identification method based on vibration test technology is the hotspot and difficulty in research at home and abroad.In this paper,on the basis of the modal data(frequency and vibration mode),combined with the frequency response function,the related numerical simulation has been researched on a plane rigid frame structure,providing a theoretical basis for the structural damage identification and real-time health monitoring.For large complicated structure,under the condition of knowing the probably local damage location,the concept of substructure has been introduced,changing global identification to local identification.The substructure interface displacement condensation method is used to divided the whole structure into several substructures,then condensed stiffness matrix and mass matrix in each substructure.On the basis of the condensed stiffness matrix and mass matrix to local damage identification.For the actual large complex structure,theory of degrees of freedom is often greater than the measured degree of freedom.In order to achieve the purpose of the match of measured degree of freedom and the theory of degrees of freedom,in this paper,the improved Guyan condensation method is used to condensation off the structure.Compared with Guyan condensation,this method has solved the large errors problem that the produced by the Guyan condensation.In additon,in order to simulate the actual measurement error,this paper considers the effect of noise.On the basis of the substructure,the frequency response function has used to identify the damage.Damage identification method of frequency response function can be divided into three stages:qualitative,positioning and quantitative.First of all,the frequency response function curve is used to analyse the structure damage detection.Secondly,judging the damage location though the change of the different nodes and the degrees of freedom.Finally,according to the formula of damage degree to calculate the degree of damage of the damage unit.MATLAB and ANSYS are used to unmerical simulation in this paper,the results show that the method can achieve satisfactory degree.