Analysis of large amplitude vibration mechanism of Shinkansen PRC girder bridges and the long-term trend of their structural characteristics

Abstract

Recently, some PRC girder bridges of Shinkansen were found to have unexpected large amplitude vibration. The girders' natural frequency estimated by the impact test was 13 % larger than the excitation frequency caused by Shinkansen passing. Thus, the mechanism cannot be simply explained as resonance in the linear system. We conducted vibration measurement and found the natural frequency becomes lower as amplitude becomes larger. By conducting FE analysis considering the effect of the amplitude-dependent nonlinearity of stiffness and Shinkansen's vehicles weight, natural frequency is found to decrease and get close to the excitation frequency and instantaneous resonance during Shinkansen passing can occur. We also analyzed the long-term trend of structural characteristics by using the vibration data continuously measured for several years. Then, we found the natural frequency varies clearly depending on the temperature.