1. Research Engineer, Sumitomo Mitsui Construction Co. Ltd., Technical Research Institute, 518-1 Komaki, Nagareyama City, Chiba ken 270-0132, Japan.
2. Professor, Dept. of Civil and Environmental Engineering, Faculty of Engineering, Yamaguchi Univ., 2-16-1 Tokiwadai, Ube, Yamaguchi ken 755-8611, Japan.
3. Reader, Dept. of Civil and Structural Engineering, Univ. of Sheffield, Mappin St., Sheffield, S1 3JD, UK.
4. Chief Research Engineer, Sumitomo Mitsui Construction Co. Ltd., Technical Research Institute, 518-1 Komaki, Nagareyama City, Chiba ken 270-0132, Japan.
5. Research Student, Dept. of Civil and Environmental Engineering, Faculty of Engineering, Yamaguchi Univ., 2-16-1 Tokiwadai, Ube, Yamaguchi ken 755-8611, Japan.