1. Dept. of Civil Engineering, Ishikawa National College of Technology, Tsubata Ishikawa 929‐0392 JAPAN
2. Dept. of Civil Engineering, Chuo University, Kasuga, Bunkyo‐ku, Tokyo 112‐8551 JAPAN
3. Research Laboratory, Taisei Rotec Corporation, Kamiya Konosu Saitama 365‐0027 JAPAN
4. Research Laboratory, Sato Road Corporation, Sanda Atsugi Kanagawa 243‐0211 JAPAN