1. Ph.D. Candidate, Dept. of Civil Engineering, Beijing Jiaotong Univ., Beijing 100044, China (corresponding author).
2. Professor, Dept. of Civil Engineering, Beijing Jiaotong Univ., Beijing 100044, China.
3. Associate Professor, Dept. of Foreign Studies, Xi’an Univ. of Arts and Science, Shaanxi, Xi’an 710065, China.
4. Ph.D. Candidate, Dept. of Civil Engineering, Beijing Jiaotong Univ., Beijing 100044, China.
5. Dept. of Civil Engineering, Beijing Jiaotong Univ., Beijing 100044, China.