Bridge Damage Identification Method Based On Blind Source Separation

As the role of bridges in the current traffic system becomes more and more important,people pay more and more attention to the health monitoring of bridge structures.Damage identification is one of the core issues in structural health monitoring.The traditional structural dynamic characteristics are used as damage indicators.Damage identification methods are developing rapidly,but traditional methods will be disturbed by environmental temperature factors in the actual monitoring process,resulting in unsatisfactory damage identification results.Therefore,in order to solve the problem that the results of structural damage identification are susceptible to environmental temperature and noise,this paper introduces the blind source separation technology used to separate mixed signals in the field of signal processing,and proposes a bridge damage identification based on the AMUSE algorithm in blind source separation.Method,the feasibility and effectiveness of this method in denoising bridge damage identification are verified by finite element numerical simulation test.The main research content of this article:(1)Explain the related theories of blind source separation and carry out simulation signal experiments on this basis.Firstly,the mathematical model,preprocessing technology,algorithm uncertainty and evaluation criteria of blind source separation are introduced.Considering the applicable scope of the algorithm,the AMUSE algorithm is selected from four typical algorithms,the function mixed signal generated by MATLAB and the collected speech mixed signal are unmixed,and the similarity coefficient and mean square error of the signal before and after separation are calculated,and the AMUSE algorithm is clarified seperate effect.(2)Analysis of the mechanism of the influence of ambient temperature on the modal frequency of the structure.Based on the Fourier heat conduction theory,the basic concepts of the temperature field and temperature load of the structure and three common heat transfer methods are introduced,and the specific calculation formula of the temperature load is given;from the influence of the temperature on the elastic modulus of the structure material and the temperature Starting with two aspects of the influence of structural boundary conditions,it is determined that the change in the elastic modulus of structural materials caused by temperature changes is the main reason for the influence of temperature on the modal frequency of the structure.Finally,a rectangular cross-section beam bridge is taken as an example.In the two cases of fixed beams,based on the theory of structural dynamic characteristics,the functional formula of the influence of ambient temperature on the bridge modal frequency is obtained.(3)Feasibility analysis of damage identification based on AMUSE algorithm of blind source separation.First,taking the finite element model of a simply supported beam as an example,through numerical calculations in ANSYS,the effects of temperature effects and structural damage on the modal frequency of the simply supported beam are specifically explored.The results show that the temperature effect is an important factor in the change of the modal frequency of the structure.The reason is to further verify the accuracy of the derivation of the elastic modulus theory of temperature-affected structures,and then use the AMUSE algorithm to identify 21 different damage conditions,which shows that the method can be used under different damage levels or different damage positions.,Can eliminate the interference of temperature,and accurately identify the damage.(4)The validity verification of AMUSE algorithm based on blind source separation in practical engineering applications.Take a finite element model of a single-box double-chamber curved girder bridge as an example.In the finite element model of the curved girder bridge,three types of damage are set: mid-span,pier,mid-span,and pier simultaneous damage.,Damage is unknown,noise interference is considered,and the damage is further developed.The damage identification is performed on the three damage situations.The identification results show that the method can still eliminate the temperature influence in the actual project to complete the damage identification work,and has a good robustness to noise.