1. Sr. Res., Res. and Devel. Ctr., Nippon Koei Co., Ltd., 2304 Inarihara, Kukizaki-machi, Inashiki-gun, Ibaraki 300-1259, Japan.
2. Prof., Grad. School of Sci. and Technol., Kumamoto Univ., Kurokami 2-39-1, Kumamoto 860-8555, Japan.
3. Res., Res. and Devel. Ctr., Nippon Koei Co., Ltd., 2304 Inarihara, Kukizaki-machi, Inashiki-gun, Ibaraki 300-1259, Japan.
4. Asst. Mgr., Constr. Engrg. Ctr., Tokyo Electric Power Co., 1-3 Uchisaiwai-cho 1-chome, Chiyoda-ku, Japan.