[1] Grad. Sch. Sci. and Eng., Ibaraki Univ., Nakanarusawa, Hitachi, 316-8511, Japan
[2] Dept. Civ. Eng., Meijo Univ., Tenpaku-ku, Nagoya, 468-8502 Japan, Japan
[3] Dept. Urb. and Civ. Eng., Ibaraki Univ., Nakanarusawa, Hitachi, 316-8511, Japan
[4] JCK Co. Ltd., Imaike, Anjo, 446-0071, Japan