1. Researcher, Port and Airport Research Institute, 1-1, Nagase 3-Chome, Yokosuka City, Kanagawa 239-0826, Japan.
2. Associate Professor, Dept. of Civil Engineering, Univ. of Auckland, Private Bag 92019, Auckland 1142, New Zealand (corresponding author).
3. Professor, Dept. of Civil Engineering, Yamaguchi Univ., Tokiwadai 2-16-1, Ube, Yamaguchi, Japan.
4. Assistant Professor, Dept. of Civil Engineering, Yamaguchi Univ., Tokiwadai 2-16-1, Ube, Yamaguchi, Japan.