1. Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, P. R. China
2. Key Laboratory of High-Speed Railway Engineering, Ministry of Education, Southwest Jiaotong University, 610031 Chengdu, P. R. China
3. School of Civil Engineering, Central South University, Changsha 410075, P. R. China
4. National Engineering Laboratory for High Speed Railway Construction, Changsha 410075, P. R. China
5. China Railway Design Corporation, Tianjing 300142, P. R. China
6. Department of Civil, Environmental and Ocean Engineering, Stevens Institute of Technology, NJ 07030 Hoboken, USA