1. Ph.D. Student, School of Civil Engineering, Beijing Jiaotong Univ., Shangyuancun 3, Haidian District, Beijing 100044, PR China.
2. Professor, School of Civil Engineering, Beijing Jiaotong Univ., Shangyuancun 3, Haidian District, Beijing 100044, PR China (corresponding author).
3. Professor, School of Civil Engineering, Beijing Jiaotong Univ., Shangyuancun 3, Haidian District, Beijing 100044, PR China.