2023 Volume 79 Issue 15 Article ID: 22-15015
There is concern about high-frequency vibration in steel bridge members with rail joints. However, modal damping for higher-order local vibration modes over 100 Hz is still an open program. In this study, the existing modal identification method using multi-point hammering and the reciprocity theorem that can be used in the field test is improved. A simulated generation method of free vibration responses measured synchronously at multiple sensors is developed by the inverse Fourier transform of the transfer function. The proposed method is applied to full-scale railway steel I girder bridge web members. As a result, the modal characteristics of the web members up to 2,000 Hz are clarified. In addition, the resulting modal damping ratios and natural frequencies relationship indicate that most high-order local vibrations over 300 Hz have a small modal damping ratio below 1 %.
