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Wang, Xiaoguang

Civil and Environmental Engineering

2005

MS

The purpose of this study is to find the resonant frequencies of a member with axial load and lateral stiffness. The ties and ballast stiffness are simulated by elastic Winkler stiffness. The rail and I-beam tested are assumed to be Euler beams with both ends pinned. In this thesis, the continuous model is used including the effect of axial compression. Due to the irregular cross section of the rail tested, the shear center does not coincide with the center of gravity. Further lateral stiffnesses from rails simulated by springs in the experiment do not act at the shear center, thus causing additional torsion. This incurs coupling between lateral displacement and torsional rotation. In previous investigation, the torsional frequencies were assumed to be much higher than the bending frequencies and were not considered (Boggs 1994) (Beliveau and Muiray 1996). The resonant frequencies obtained from experiments were believed to be the bending frequencies. This assumption was inadequate. It is necessary to 'determine coupled lateral-bending vibrations. Theoretical and experimental results indicate that the coupled lateral torsional frequencies get smaller as the axial compression increases.