Experimental evaluations of track structure effects on dynamic properties of railway bridges

Abstract

The dynamic stability under the passage of a moving train has become one of the most important issues in railway bridge designs. A precise application of the dynamic properties of a structure will lead to a precise description of the dynamic behavior of a structure under moving train loads. A railway bridge is completed with a track structure, which is composed of rail, sleeper and track (concrete or ballast). A track structure can change the modal properties of the railway bridge, through the contribution of stiffness as well as mass effects. Consequently, the critical speed of the train that gives rise to the resonance behavior should be also changed, with or without the track. In the present study, a twin I-shaped steel composite girder bridge was fabricated as a test specimen, and modal testing was carried out with the installation of non-ballast, ballast track and concrete track. Modal tests were performed with hydraulic dynamic actuators. The natural frequencies, damping ratios and dynamic responses of each type of track structure were observed, along with the variation of magnitudes, frequencies and amplitudes of dynamic loading. From the results, the effects of a track structure on the railway bridge can be evaluated.