Research On Damage Identification Method For Girder Of Long-span Cable-stayed Bridge

Structural damage identification is an important part of structural health monitoring system of long-span bridges. Because dynamic information can be measured by the pulsating of the environment in the course of running structure, the damage detection method based on dynamic information can be used to monitor on-line. The main work of this paper is follows:1. Introduced the basic theory of frequency response analysis, and the basic method of dynamic data identification.2. In order to find damage identification, this paper proposed a two-stage method to evaluate the status of existing structures. The variations of displacement modes are used to identify the damage location. Using these data as the input parameter vectors for neural network to identify the damage extend. Numerical simulation of a cantilever beam is applied to verify the method. These results demonstrated that the proposed method is feasible for the damage identification.3. Damage identification method based on curvature modal is used to solve the multi-damage problem. The two-stage method, which is the same as the method based on displacement modal, is used to identify the damage location and extend. The same examples is used to confirm this method and compare with the method based on displacement modal. The result shows that the method based on curvature modal can identify the locations more than one damages.4. Some studies is done to identify the damage location in actual structures. The changes of dynamic characteristic subjected to various typical damages which is respect to numerical simulation of Ruangyang Cable-stayed Bridges. A finite element model of the cable-stayed is established. Some analysis of sensitivity of dynamic characteristic for girder damaged. Conclusions as follows: The frequency variations of Ruangyang Cable-stayed Bridges are very little. The difference of curvature modals are used to identify the approximately damage location. The index Z, which is calculated by curvature modals, is used to identify the damage location of girder. Because the index Z has material value, the damage can be judged by value.