1. Graduate Student, State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji Univ., Shanghai 200092, China (corresponding author).
2. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of Illinois, Urbana, IL 61801.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois, Urbana, IL 61801.
4. Professor, State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji Univ., Shanghai 200092, China.