1. School of Civil Engineering, Southwest Jiaotong University , Chengdu, P.R. China
2. Key Laboratory of High-Speed Railway Engineering, Ministry of Education, Southwest Jiaotong University , Chengdu, P.R. China
3. Key Laboratory for Special Area Highway Engineering of Ministry of Education, Chang’an University , Xi’an, P.R. China
4. School of Highway, Chang’an University , Xi’an, P.R. China
5. Department of Civil and Environmental Engineering, University of Wisconsin – Madison , Madison, WI, USA