1. Associate Professor, Dept. of Civil Engineering, Zhejiang Univ., A-725 Anzhong Bldg., 866 Yuhangtang Rd., Hangzhou, Zhejiang 310058, China (corresponding author).
2. Graduate Student, Dept. of Civil Engineering, Zhejiang Univ., A-818 Anzhong Bldg., 866 Yuhangtang Rd., Hangzhou, Zhejiang 310058, China.
3. Professor, Dept. of Civil Engineering, Zhejiang Univ., A-821 Anzhong Bldg., 866 Yuhangtang Rd., Hangzhou, Zhejiang 310058, China.
4. Undergraduate Student, Dept. of Civil and Environmental Engineering, Bucknell Univ., 701 Moore Ave. C1334, Lewisburg, PA 17837.