Structural Damage Localization Of Bridges Based On Dynamic Signatures

Traffic is a social economic blood, and a bridge is a traffic throat .The development of social economy will be limited if the traffic doesn't move to and from, so it is very important to make sure every bridge's function and safety. To use every bridge normally as demands to test or monitor to bridges' safety from now and then. At present there are a large quantity of bridges in our country. One hand, many old bridges have approached their design lifetime, their components have aged and be damaged. On the other hand, a number new and large-scale bridges will be built. To assure these bridges' safety and avoid accidents, we should get on monitor on-line to new bridges, and detect damage and identify reliability to old bridges.For large-scale structures, it is very difficult to simultaneously identify the location and extent of element-level damage by using of the limited modal measurements, which often leads to wrong results of damage identification. The methodology , which is composed by the global identification and local identification, is an effective approach to identify the structural damage in complex structures. And then the local damage identification of beam-like structures is studied with modal measurements based on local vibration. The main contents of the dissertation are listed as follows.Firstly, In this Paper, after a brief overview of the development of bridge health monitoring, the connotation of bridge health monitoring is Pointed out in an extended sense.And then, Actuality of damage identification for structures is expatiated and comments are made on the methods of them. These methods include natural frequency, strain modal shape, COMAC, flexibility matrix, wavelet analysis, genetic algorithms etc.Finally, through some of numerical simulation to a continuous beam bridge, local damage localization based on dynamic signatures is Presented. The applicability of three dynamic signatures based frequency data are studied, and the numerical simulations of different damage cases are carried out. The resultsdemonstrate that the normalized change ratio of frequency is stable as changing the damage location and extent. Therefore, the normalized change ratio of frequency is selected as dynamic signature of beam-like structures based on local vibration. The effectiveness of the damage localization by using of the proposed dynamic signature is illustrated by a numerical example.