1. Professor, National Engineering Laboratory for High Speed Railway Construction, School of Civil Engineering, Central South Univ., 22 Shaoshannan Rd., Changsha 410075, China.
2. Graduate Student, School of Civil Engineering, Central South Univ., 22 Shaoshannan Rd., Changsha 410075, China.
3. Professor, Dept. of Architecture and Building Engineering, Kanagawa Univ., 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan; School of Civil Engineering, Central South Univ., 22 Shaoshannan Rd., Changsha 410075, China (corresponding author).