1. Ph.D. Candidate, College of Civil Engineering, Hunan Univ., Changsha, Hunan 410082, China.
2. Professor, College of Civil Engineering, Hunan Univ., Changsha, Hunan 410082, China (corresponding author).
3. Professor, Dept. of Civil, Architectural and Environmental Engineering, Univ. of Miami, Coral Gables, FL 33146.
4. Senior Engineer, Design and Planning Institute of Communication of Hunan Province, Hunan 410008, China.
5. Senior Engineer, Dept. of Transportation of Hunan Province, Hunan 410004, China.