1. Ph.D. Candidate, School of Civil Engineering, Beijing Jiaotong Univ., Beijing, 100044, P.R. China; and Assistant Professor, College of Architecture and Civil Engineering, Beijing Univ. of Technology, Beijing, 100124, P.R. China.
2. Professor, School of Civil Engineering, Beijing Jiaotong Univ., Beijing 100044, P.R. China (corresponding author).
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Houston, TX.