1. Associate Professor, Dept. of Civil & Environmental Engineering, Yonsei Univ., Seoul 120-749, Korea.
2. Ph.D. Candidate, Dept. of Civil & Environmental Engineering, Yonsei Univ., Seoul 120-749, Korea.
3. Ph.D. Student, Dept. of Civil & Environmental Engineering, Univ. of California Berkeley, Berkeley, CA 94720.
4. Assistant Professor, Dept. of Civil & Environmental Engineering, Yonsei Univ., Seoul 120-749, Korea (corresponding author).
5. Project Manager, Ultra Construction Co., Seoul, Korea.