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Natural Vibration Analysis
To know the characteristic of the structure that shows complex behavior like suspension bridge and cable-stayed bridge, the natural vibration analysis is known to be effective. It knows whether the vibration of the structure is composed of what mode element, and the natural vibration analysis is indispensable to dynamically checking the structure. Moreover, in general, not only one vibration element but also various mode of vibrations mix each other and vibrate when the structure vibrates. The vibration will be composed of a lot of mode of vibrations if the structure is a large-scale, or complex like suspension bridge and cable-stayed bridge. In a word, because the vibration pattern due to the earthquake can be judged easily by knowing the vibration characteristic of the structure, the design that defends the structure from a wind loading and a traffic load, etc. is enabled. Then, the following researches are done in our laboratory.
ex.1: The Vibration Characteristic of Twin Composite Girder Bridge
Today, under the situation in which a lot of new problems like the cost reduction of public works and consideration to the global environment occur, the construction case of the rationalized bridge like twin main girder bridge with PC slab increases. PC slab enables the decrease of the number of structural members by enlarging the interval of the main girder. On the other hand, there is a possibility of becoming a problem in respect of aerodynamic, because the twin composite girder bridge has a portrait section compared with a past girder bridge. Moreover, it can be said that the torsional stiffness of twin girder bridge is relatively low, because it doesn't have lateral bracings and is basically open cross section. In addition, when the wind stability is discussed, we should take natural frequency in consideration. Then, in this research, analysis for the twin I-girder bridge with PC slab is performed, and we examine the design of bridge steady compared with wind load.
ex.2: Natural Vibration Analysis based on Deflection Theory
Deflection theory is a theory thought that the displacement of stiffening girder of the suspension bridge is equal to that of the cable. And, the construction of long span suspension bridge could become possible by this Deflection theory. Moreover, the natural frequency can be calculated by solving strain energy and kinetic energy for stiffening girder and the cable, and these rule equations by using Deflection theory. Then, in this research, natural vibration analysis of the suspension bridge that has asymmetry span is conducted based on Deflection theory, and we examine the applicability of Deflection theory in the suspension bridge that has asymmetry span by the comparison with the measurement value.