1. Saitama University; Department of Environmental Science & Civil Engineering; 255 Shimo-okubo, Sakura-ku Saitama 338-8570 Japan
2. Civil Engineering Research Institute for Cold Region; 1-34, 1-jo 3-choume Hiragishi, Toyohira-ku Sapporo, Hokkaido 062-8602 Japan
3. Rubber Bearing Association; 1-5-26 Akasaka, Minato-ku Tokyo 107-0051 Japan