1. Professor, Dept. of Civil and Environmental Engineering, Hanyang Univ., 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea.
2. Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Hanyang Univ., 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea.
3. Research Professor, Dept. of Civil and Environmental Engineering, Hanyang Univ., 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea (corresponding author).