The Damage Identification Method Of Track Structure Based On Virtual Distortion Method

The track structure will inevitably have some diseases under the influence of train dynamic load,temperature and other environmental factors,which adversely affect the comfort and safety of train operation.The damage identification method based on structural dynamic response utilizes the most basic dynamic characteristics of the structure and has been widely promoted and applied in the field of civil engineering.However,due to the concealment of structural damage and the small impact on the dynamic response of track structure,it is still difficult to identify the damage accurately.Therefore,the basic theory of additional virtual mass method based on virtual distortion method(VDM)and its application in damage identification of track structure are studied according to the characteristics of structural damage.The main research contents are as follows:(1)An improved objective function damage identification method based on VDM.The frequency and mode shapes in the traditional objective function are replaced by structural frequency response.And it can be calculated quickly by VDM,which avoids the re-calculation of structural system matrix and eigenvalue analysis in the process of structural optimization.So the optimization efficiency can be improved.The effectiveness of the proposed method is verified by numerical simulation of an eight-story frame structure under various damage cases.(2)The virtual mass estimation method based on structural frequency response.On the basis of the additional virtual mass method based on VDM,a direct estimation method and an improved estimation method for the additional virtual mass are studied on the premise of setting the structural excitation frequency.The numerical simulation results are given by using the simple supported beam model,which verifies the effectiveness of the proposed method.(3)The establishment of three-dimensional finite element model(FEM)of track structure.A three-dimensional FEM of track structure is established by ANSYS.The determination of model parameters,the selection of element types of different structural components,the key points of meshing,the selection of modeling length and the treatment of boundary conditions are discussed in detail.The natural frequencies and mode shapes of track structure are obtained by modal analysis.(4)The damage identification of track structure.A simplified method of threedimensional FEM of track structure is presented based on model condensation.And the direct estimation and improved estimation method of additional virtual mass are applied to track structure.Then,the additional mass value and structural modal information are used to identify the structural damage,and the applicability and validity of the proposed method in track structure are verified.