Modal Parameter Identification Of Asynchronous Measured Bridge Based On Stochastic Subspace Method

Structural modal parameter identification is the premise and basis of structural health monitoring,and it is also the main content of structural dynamic recognition.As a method of structural modal parameter recognition,the stochastic subspace identification method is widely used in engineering health monitoring because it has many advantages such as not interrupting the normal use of the structure during use and convenient and time-saving.The stochastic subspace identification method directly acts on the measured time history response data.When the time of the measured data is not synchronized in the process of signal acquisition,it will affect the results of structural modal identification.Therefore,it is necessary to explore the identification of asynchronous measured data by using the random subspace method.With the help of ANSYS finite element simulation and laboratory tests,this paper studies the modal identification of structures using stochastic subspace method under asynchronous measured response data.The main work and conclusions of this paper are as follows:1.Several common modal identification methods are introduced,and their basic theory and specific algorithm are described.The traditional parameter identification method and the parameter identification method under environmental excitation are introduced in detail,and their advantages and disadvantages are compared through the application scenarios and application modes of each method.2.The research and progress of data time synchronization are systematically summarized.It is recognized that the time synchronization of dynamic response data at different signal acquisition positions of the structure will cause time synchronization error,which will lead to the change of structural modal shape.The time synchronization methods and their advantages and disadvantages under different conditions are analyzed.On this basis,an algorithm model using structural state space model to identify the acceleration time delay between different measuring points is proposed.3.In order to test the proposed time delay identification algorithm,the identification algorithm is verified by finite element simulation and laboratory test.After identifying the time delay between asynchronous measured data,the data is corrected,and the modified data is identified by stochastic subspace identification method.It is found that the modal identification result of the modified data is closer to the real modal of the structure,and the proposed time delay identification algorithm has satisfactory performance for the identification of asynchronous measured data.