1. Lecturer, Faculty of Civil Engineering, Ho Chi Minh City Univ. of Technology, Ho Chi Minh City, Vietnam; formerly, Postdoctoral Research Fellow, The Univ. of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan (corresponding author).
2. Professor, Dept. of Civil Engineering, The Univ. of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.