Dynamic Analysis Of Long-span Cable-stayed Bridge And Damage Identification Of The Main Girder

In the operating process, bridge structure would damage, as the result of design, construction, environment, overload and many other reasons, and the damage can affect the normal use and safety of the bridge structure. To ensure the safety of bridge structures, damage must be detected and identified, particularly for long-span bridges. Cable-stayed bridge is much more favored in cross-river or cross-sea bridge.It is practical significant to studying the damage identification of long-span cable-stayed bridge.The effect of structural damage identification on the one hand is related to the finite element model, establishing the model which can reflect the real performance is particularly crucial;the other is the identification method which will be applied.Taking Jiujiang Yangtze River Bridge as the engineering background, the spatial finite element model is established using finite element software ANSYS, free vibration is conducted after determining the reasonable finished state of the bridge. Some simplification are applied for improving the computational efficiency. For example the U-stiffener in the top and bottom of steel box girder are substituted by physical anisotropic plate shell elements, which its parameters are determined according to the equivalent stiffness methods;For the prestressed steel strands, the prestress steel strands are simulated by LINK 10 elements, the prestress is applied by estimating the value of effective stress.Currently the undamaged structure is taken as the baseline model of damage identification in modal strain energy (MSE) theory. But the undamaged baseline models of the bridges are difficult to obtain when the bridge has serviced for a long time or is lack of design information. The MSE damage identification method taking damaged structure as the baseline model is developed theoretically. The numerical simulation of a continuous box beam bridge show that the results are sensitive to growth of old damage, single new damage, intensive damage, multiple injuries, and the original damage doesn't interfere the identification of new developed damage. At the same time, the MSE damage identification method is applied in Jiujiang Yangtze River Bridge's main girder. Numerical simulation results show that it is also suitable in large-span cable-stayed bridge,and is sensitive to different damage cases.