1. Associate Professor, Dept. of Civil Engineering, Zhejiang Univ., A-823 Anzhong Building, 866# Yuhangtang Rd., Hangzhou, Zhejiang 310058, China.
2. Graduate Student, Dept. of Civil Engineering, Zhejiang Univ., A-818 Anzhong Building, 866# Yuhangtang Rd., Hangzhou, Zhejiang 310058, China.
3. Professor, Dept. of Civil Engineering, Zhejiang Univ., A-821 Anzhong Building, 866# Yuhangtang Rd., Hangzhou, Zhejiang 310058, China.
4. Lecturer, School of Aeronautics and Astronautics, Zhejiang Univ., 38# Zheda Rd., Hangzhou, Zhejiang 310027, China (corresponding author).