1. Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, South Korea.
2. Researcher, Korea Bridge Design and Engineering Research Center, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, South Korea; formerly, Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, South Korea.
3. Professor, Dept. of Civil and Environmental Engineering, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, South Korea (corresponding author).