Study On Damage Identification Of Frame Structure Based On Model Updating Of Frequency Response Function

Structural damage identification,as an important part of structural health monitoring,has become a research hotspot in this field.As one of the structural damage identification methods,the model updating method of the frequency response function?FRF?can be used to identify the damage through the experimental FRF.The experimental FRF are easier to obtain,while avoiding the modal analysis errors.However,with the large and complicated structure,when applying the model updating method of FRF to damage identification,it faces the problems of less test information,too many updating parameters and so on.The substructure method can identify damage to large and complex structures.By dividing the substructure,it can reduce the number of identification parameters and save experimental equipment.Therefore,this paper proposes a damage identification method combining substructure method and model updating method of FRF.A substructure damage identification method based on the acceleration FRF of model updating is proposed,it constructs a target equation for the measured FRF.Only the finite element model?FEM?of the substructure to be identified,the system mass and stiffness matrix of the assembled substructure,the transformation matrix of the second DOF reduction can be solved iteratively.For the ill-posed problems,L₁ norm regularization is used to solve.Numerical simulations of a three-story two-span frame structure and a six-story steel frame structure verify the effectiveness of the method.The experimental research on the six-story steel plan frame further proves the accuracy of the method and the applicability of the experiment.From the research and analysis of this article,several conclusions are drawn:?1?In the study of three different DOF reduction methods,it is concluded that the IRS method can achieve more accurate results,if the calculation requirements are met.?2?The substructure damage identification method based on the FRF of model updating proposed in this paper can accurately identify the damage location and degree under different damage conditions.At the same time,compared with the recognition results of the overall structure of the model correction method based on FRF,the method proposed in this paper can accurately identify the damage only with fewer measurement points,the iterative convergence effect is good,and the calculation is short.?3?The selection of frequency points,the arrangement of measurement points and noise interference are all factors that affect the recognition results.The selected frequency point should be in the resonance region,and the range of the FRF is obviously different before and after the damage,and it should be within the monotonically curve segment.The arrangement of measurement points should be more sensitive to the FRF,and noise is also an important factor.The research analysis shows that the results obtained by using the substructure damage identification method in this paper are accurate and reliable under certain noise interference.?4?The experimental analysis of a six-story steel frame verified the feasibility and effectiveness of the proposed method.The experimental results show that the method can accurately identify the damaged members in the substructure.Therefore,the actual identification of the substructure damage identification method based on the FRF of model updating is reasonable and effective.