1. Ph.D. Candidate, Dept. of Structural Engineering, Tongji Univ., Siping Rd. 1239, Shanghai 200092, China.
2. Professor, Institute of Industrial Science, Univ. of Tokyo, Tokyo 1538505, Japan.
3. Professor, Dept. of Structural Engineering, Tongji Univ., Siping Rd. 1239, Shanghai 200092, China (corresponding author).