Research On Damage Detection Algorithm Of Steel Structure Based On Wavelet And Transmissibility Function

With the rapid development of economy and science and technology,all kinds of complex spatial structures are increasing,and the working condition and stress of these engineering structures are very complicated,so the damage can not be avoided.Due to long-term influence of unmeasurable forces such as wind force and water flow,only the output response of the structure surface can be measured through the sensors,when the damage detection is performed on these structures.Therefore,it is extremely difficult to detection damage of large and complex structures.The accurate location of damage position is the precondition of building reparing,which is of great significance to ensure the safe and stable operation of engineering structure.The method of structural damage detection by using the transmissibility function was discussed in this paper,and the feasibility of the algorithm was verified by theoretical deduction,simulation and experiment,the main research work and results are as follows:Firstly,based on the motion differential equations with multiple degrees of freedom,the frequency response characteristics of the vibration acceleration signals under external excitation were researched,and the system damage transmissibility function model was established.On this basis,a structural detection method based on the change quantity of damage structure transmissibility function in a certain frequency domain as damage index was proposed.and combined with the recursive algorithm law of symmetric tridiagonal matrices,the sensitivity of damage index algorithm to structural local damage was presented.The algorithm had the advantages of simple operation process and high accuracy,which can realized structural damage detection and location without the need of external excitation information.Secondly,according to the problem that the traditional transmissibility function had insufficient sensitivity to the small local damage of the structure,the method of calculating damage index based on the wavelet transmissibility function was proposed in this paper.Then,combined with the basic theory of wavelet analysis,the sensitivity of the wavelet transmissibility function damage detection method was analyzed to verifie the feasibility of the algorithm theoretically.Thirdly,multilayer frame model,portal frame model and two damage modes were bulid on ANSYS to verify the accuracy of the damage detection algorithm under different damage modes in these two damage models;The relations between damage stitution and damage index were discussed in multilayer frame model.The reliability of the damage index of traditional transmissibility function and the damage index of wavelet transmissibility function in different damage models and different damage modes are compared by Matlab.Finally,the experimental platform of damage detection for portal frame is constructed,and the damage detection method based on traditional transmissibility function and wavelet transmissibility function under different damage modes is validated experimentally.The experimental results show that the damage detection method presented in this paper can effectively and accurately realize local damage localization,which is of practical value for the development of damage detection technology for large complex spatial structures.