Structural Damage Identification Based On Wavelet Packet De-noising And FE Model Updating

The development of a methodology for accurate and reliable condition assessment of civil structures has become very important. The FE model updating method provides an effective, non-destructive, global damage identification technique. Through the finite element model modification technology for high precision mode, the finite element model services for structural response prediction, optimization design, reliability analysis, breakage detection and fault diagnosis etc. At present, the method based on the sensitivity analysis is the most mature.Damage identification based on model modification firstly establishes structure model of initial non damage, through comparing the difference of the finite element model and the practical structural dynamic characteristics, revising the stiffness, quality, damping model parameters of model, improving analytical model and experimental results of correlation, eventually on revising finite element model using local stiffness reduction to indicate the damage location and degree of structure. The FEM updating methods with measured modal parameter identification damage from the view of mathematics belongs to a kind of inverse problem solving. However, the solving of inverse problem is sensitive with input error, and as the input parameters, measured modal parameters, due to the inevitable environmental noise, instrument accuracy etc, the accuracy of the testing error is difficult to meet the requirements needed model modification, which often leads to structural damage identification misjudgment even failure.The accuracy of finite element model updating for structural damage identification is easily affected by the noise in the measured modal, so wavelet packet de-noising is introduced to reduce the impact of noise. In each iteration step, the wavelet packet de-noising treatment is applied to the difference between measured modal and simulated modal from the finite element model because the time-frequency characteristic of actual modal is different from noise modal. The modal parameters after de-noising are used to construct objective function for modal updating, and the optimal question is solved to determine the stiffness in FM model. Finally, the stiffness change can indicate the damage position and magnitude. In this paper, the method proposed in this paper is used to identify the location and extent of damage in a three-span continuous beam.The numerical analysis shows the proposed method can improve the robustness of finite element model updating for the structural damage identification.This paper adopts a different kind of method, the data smoothing method to process the modal noise, damage identification results show that this method can improve the finite element model modification method for structural damage identification robustness. Meanwhile adopting different model modification target function composed of eigenfrequencies and curvature modes is used to identify the damage, damage identification results show that this method can identify the structural damage position and magnitude.