1. Assistant Professor, School of Civil and Environmental Engineering, Nanyang Technological Univ., 50 Nanyang Ave., Singapore 639798.
2. Postdoctoral Fellow, School of Civil Engineering and Mechanics, Huazhong Univ. of Science and Technology, Wuhan, Hubei 430074, China.
3. Professor, School of Civil Engineering and Mechanics, Huazhong Univ. of Science and Technology, Wuhan, Hubei 430074, China. (corresponding author)
4. Professor, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742-3021.