IDENTIFICATION OF HIGH-ORDER LOCAL VIBRATION MODES USING MULTI-POINT EXCITATION AND DYNAMIC BEHAVIOR OF I-SHAPED GIRDER STEEL RAILWAY BRIDGE

Abstract

 High-order local vibration modes over 200 Hz of steel railway bridges with complicated vibration mode shapes are related to noise along the railway. However, they have not been fully elucidated due to restrictions on the number of sensors and synchronization accuracy. In this study, authors utilized a new method for identifying higher-order local vibration modes that can be implemented in field tests by substituting multipoint hammering for multipoint measurements using the reciprocity theorem and phase standardization method. Thereafter verifying the accuracy, it was applied to the steel railway I-shaped girder bridge members with direct fastening track system, and it was clarified that the vibration modes can be identified up to about 1200 Hz, which is high-order and complicated such as 7th order of the web. In addition, by analyzing with the measured responses under train passages, it is empirically demonstrated that the high-order local vibration modes of 200 to 600 Hz are superior due to the resonance with the excitation frequency caused by the periodic rail irregularity in the target bridge.