1. Chief Researcher, Track & Roadbed Research Team, Korea Railroad Research Institute, Uiwang 16105, Korea (corresponding author).
2. Chief Researcher, Track & Roadbed Research Team, Korea Railroad Research Institute, Uiwang 16105, Korea.
3. Senior Researcher, Advanced Infrastructure Research Team, Korea Railroad Research Institute, Uiwang 16105, Korea.
4. Associate Professor, Dept. of Civil Engineering, Kyungsung Univ., Busan 48434, Korea.
5. Researcher, Track & Roadbed Research Team, Korea Railroad Research Institute, Uiwang 16105, Korea.