[1] Dept. of Civil. Eng., Ritsumeikan Univ., Nojihigashi, Kusatsu,525-8577, Japan
[2] Japan Construction Method and Machinery Res. Inst., Obuchi, Fuji,417-0801, Japan
[3] Raito Kogyo Co. Ltd., Chiyoda-ku, Tokyo,102-8236, Japan
[4] Fudo Tetra Co. Ltd., Chuo-ku, Tokyo,103-0016, Japan
[5] Nittoc Construction Co. Ltd., Chuo-ku, Tokyo,103-0004, Japan