1. Professor, State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji Univ., Shanghai 200092, China.
2. Ph.D Student, State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji Univ., Shanghai 200092, China.
3. Professor, Dept. of Structural Engineering, Univ. of California, San Diego, CA 92093-0085 (corresponding author).