1. Dept. of Civil and Environmental Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka 239-8686 Japan
2. Research and Development Unit, Japan Ground Self-Defense Force, 5-1 Honmura-cho Ichigaya, Shinjuku-ku, Tokyo 162-8801 Japan
3. Science & Engineering Division, ITOCHU Techno-Solutions Corporation, 2-5 Kasumigaseki 3-chome Chiyoda-ku, TOKYO 100-6080 Japan
4. Institute of Technology, SHIMIZU Corporation, 3-4-17 Etchujima, Koto-ku, Tokyo 135-8530 Japan