Sangkeun Ahn

Investigation of damping in the polymer concrete sleeper for use in reduction of rolling noise from railway

The purpose of this study was to measure damping of various polymer concretes to be used as sleepers for railway. The polymer concretes consisted of epoxy monomer, hardener and aggregates. Various polymer concrete specimens were made by changing epoxy resin weight ratio and curing temperature. The dynamic properties of the polymer concrete specimens were measured by using beam-transfer function method. To predict reduction performance of the polymer concrete sleepers, an infinite Timoshenko beam model was investigated after applying measured concrete properties. The moving loads from rotating wheels on railway due to different roughness were utilized in railway vibration analysis. The vibration response was predicted from which the effects of supporting stiffness and loss factor of sleeper were investigated. The radiated sound power was predicted using calculated rail vibration response. Consequently, the sound power levels were compared for rails supported by different polymer concrete sleepers. The resu...

Railway vibration and noise reduction using particle impact dampers

Rolling noise is becoming a increasing concern for residential areas near railways. Rail vibration caused by moving loads of a train and corrugations generates noise. This study presented a particle impact dampers and its application to reduction of the rolling noise. The particle impact dampers to efficiently reduce the vibration were designed and verified using simplified models of a railway. To verify the particle impact damper performance, the vibration of a simplified railway attached with particle impact dampers was measured. The effects of different clearances and mass ratio of the damper to the railway was investigated. The numerical predictions of finite element model of impacting dampers were proposed and verified to the measured results to find the vibration reduction mechanism.

Influence of cross-sectional discontinuity on the damping characteristics of viscoelastically supported rectangular plates

Cross-sectional shape of a structure is one of the important design parameter associated with the vibration responses and resulting sound radiation. In this study, the influence of cross-sectional discontinuity on the vibration characteristics of plate structures was investigated. The variation of cross-sectional geometry in the rectangular plate was modeled as the change of bending stiffness for flexural wave propagation analysis. The complex translational and rotational stiffness at plate edges were used for modeling of the damping at the boundaries. The ratio between the incident and reflected waves from the boundaries was predicted for the flexural waves of different wavelengths to analyze the effect of support stiffness on the vibration damping. Using the wave propagation model, the condition of the viscoelastic boundary properties and the discontinuous flexural stiffness of plate for minimum reflection ratio, i.e., maximum dissipation of the vibration was calculated. Modal damping characteristics of the plate with and without the discontinuity in the cross-section were measured and compared to the predicted reflection ratios. The measured damping ratios on the different boundary conditions showed similar pattern with the predicted vibration energy dissipation at the viscoelastic supports.