1. Graduate Student, Dept. of Civil Engineering, Utsunomiya Univ., 7-1-2 Yoto, Utsunomiya, Japan 321-8585.
2. Associate Professor, Dept. of Civil Engineering, Utsunomiya Univ., 7-1-2 Yoto, Utsunomiya, Japan 321-8585.
3. Professor, Dept. of Civil Engineering, Utsunomiya Univ., 7-1-2 Yoto, Utsunomiya, Japan 321-8585.
4. Undergraduate Student, Dept. of Civil Engineering, Utsunomiya Univ., 7-1-2 Yoto, Utsunomiya, Japan 321-8585.