1. Ph.D. Student, Dept. of Civil and Environmental Engineering, Stanford Univ., Stanford, CA 94305.
2. Professor, Dept. of Bridge Engineering, Hunan Univ., Changsha, Hunan 410082, China (corresponding author)..
3. Professor, Dept. of Bridge Engineering, Hunan Univ., Changsha, Hunan 410082, China.
4. Graduate Student, Dept. of Bridge Engineering, Hunan Univ., Changsha, Hunan 410082, China.