Damage Localization Using Sensitivity Of Flexibility And Sensitivity Of Dynamic Characteristics Of Structures

The engineering structures may have some damages during their service periods, and what is more important is that when the damages have happened on some crucial parts, the damage extent would be greatly aggravated and finally result in the whole structures be destroyed without attention in time. Therefore, the technology of damage detection, evaluation and strengthening is the best active research field in modern structure engineering. Two damage location indexes that are based on flexibility sensitivity and dynamic characteristic sensitivity respectively are proposed in the thesis.The paper proposes computational methods of nodal sensitivity and elemental sensitivity based on the sensitivity of the global stiffness matrix to its elements. The state feedback control method is adopted to place the poles of the structure and the required characteristic frequencies and corresponding mode shapes of the controlled structure are obtained subsequently. The indicator of damage localization, which is used for the localization of one element and two elements' damages in a three-span continuous beam, is constituted by the second differential of eigenvalue of the structure under control with respect to the element stiffness., Numerical results indicate that the proposed method can increase the sensitivity of the indicator of damage identification to damages using the dynamic characteristic data of the structure under control while the control forces are placed at the proper positions of the structure under consideration.Based on the matrix of the flexibility of structures, the indicator of damage localization, is constituted by the sensitivity of element flexibility. The proposed damage location index is used for localizing one element and two elements' damages in a three-span continuous beam. ,Numerical results show that the indicator derived from element flexibility sensitivity can obtain good damage localization results and the diagnosis ratio can be greatly improved using the dynamic characteristic data of the structure under control if the control forces are placed at the proper positions of the structure under consideration.Beyond those, the thesis has made the comparison in the damage detection results between the ordinary flexibility matrix index and the proposed indexes in the thesis. Numerical results indicate that the two indexes discussed in the thesis are better than the flexibility matrix index in the field of damage localization.