1. Lecturer, Research Center of Geotechnical and Structural Engineering, Shandong Univ., Jinan 250061, P.R. China; formerly, Ph.D. Candidate, Graduate School of Science and Technology, Nagasaki Univ., Nagasaki 852-8521, Japan (corresponding author).
2. Professor, Faculty of Engineering, Nagasaki Univ., Nagasaki 852-8521, Japan.
3. Professor, Research Center of Geotechnical and Structural Engineering, Shandong Univ., Jinan 250061, P.R. China.
4. Assistant Professor, Faculty of Engineering, Nagasaki Univ., Nagasaki 852-8521, Japan.