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Determination of the vibration characteristics of bridge in dynamic diagnosis

On the basis of dynamic diagnosis equipment VDIK-1-10 of Russia and finite element method (FEM), the procedures for finding the exciting places and measurement points of vibration are presented. They give us clear information of diagnostic parameters. After data processing we can determine the dynamic characteristics parameters of the bridge. | Vietnam Journal of Mechanics, NCNST of Vietnam T. XX, 1998, No 2 (18 - 26) DETERMINATION OF THE VIBRATION CHARACTERISTICS OF BRIDGE IN DYNAMIC DIAGNOSIS NGUYEN CAO MENH AND PHAM XUAN KHANG Institute of Mechanics ABSTRACT. On the basis of dynamic diagnosis equipment VDIK-1-10 of Russia and finite element method (FEM), the procedures for finding the exciting places and measurement points of vibration are presented. They give us clear information of diagnostic parameters. After data processing we can determine the dynamic characteristics parameters of the bridge. The parameters obtained are used to updating modeling parameters of FEM and therefore the technical state of the bridge could be estimated. An example for inyestigation of prestressed concrete bridge with 33 m span and 10m width is illustrated. 1. Introduction Dynamic diagnosis is the close combination of computation and measurement of dynamic responses of mechanical system such as structures and bridges. After data processing one can get important measurement parameters for updating the modeling parameters of FEM, estimating technical state of the systems and, finally, to detect their damages and defects. It is difficult to reach the latest purpose quickly but the results have to be improved gradually. The dynamical monitoring and diagnosis method for bridges is now developing and improving due to the progress of informatics and measurement equipments [1, 2). New equipment set VDIK-1-10 is made by Russia for this purpose. As we know that the FEM contains a large number of degrees of freedom and only a small number of data can be measured in the limited frequency range. Therefore, there is a need of determination of location of measuring points to assure that the necessary data is collected. On the other hand, it is necessary to find out some main parameters for comparison with computation results. 2. The VDIK-1-10 Equipment 2.1. The VDIK-1-10 equipment This equipment is used for dynamic diagnosis of .