1. Professor, Dept. of Civil Engineering, Tohoku Univ., 6-6-06, Aoba-yama, Sendai 980-8579, Japan.
2. Graduate Student, Dept. of Civil Engineering, Tohoku Univ., 6-6-6, Aoba-yama, Aoba, Sendai 980-8579, Japan.
3. Postdoctoral Researcher, Dept. of Civil Engineering, Tohoku Univ., 6-6-6, Aoba-yama, Aoba, Sendai 980-8579, Japan (corresponding author).
4. Professional Engineer, CTI Engineering Co., Ltd., 4-1-25, Ichibancho, Aoba, Sendai 980-0811, Japan.