Stain Modal Parameter Identification And Damage Detection Study

Strain modal parameters is more sensitive to the change of the structural local stiffness. Structure damages can be identified based on the strain modal parameters of undamaged and damaged structure. The accuracy of the damage identification depends on the accuracy of the strain modal parameters. This paper studies the identification of the strain modal parameter and damage identification based on strain modal parameters. The main work is listed as follows:(1).The strain modal parameter identification theory and stochastic subspace identification (SSI) method are studied. The stochastic subspace model is build up. The two forms of the SSI method for modal parameter identification, data-driven and covariance based forms, are derived respectively, and the difference between these two forms is identified.(2). The element modal strain energy damage identification method is derived. The structure damage is instead of the reduction of the element stiffness. The element modal strain energy can be obtained by the modal shape of undamaged and damaged structure. Each element modal strain energy is calculated using the DS evidence theory so that the identification accuracy can be improved. The numerical results show that, single damage or more damages can be realized according to the modal strain energy damage identification index.(3). The modal strain energy method based on strain parameters is proved. The stain parameters is applied to the modal energy in the damage identification. It is proved that the modal strain energy can be calculated by the element strain modal shape, the element stiffness and the vector transformation matrix. The damage identification system form the signal of sensors to the identification of the damage is combined by the SSI method, the modal strain energy damage identification method and the DS evidence theory. The numerical results show that, the system can identify structural damage location.