1. Associate Professor, Dept. of Civil and Environmental Engineering, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, South Korea (corresponding author).
2. Associate Professor, Dept. of Civil and Environmental Engineering, Pusan National Univ., 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735, South Korea.
3. President, TM-Enc., 148 Yatap-dong, Bundang-gu, Seongnam, Gyeonggi-do 463-760, South Korea.
4. Professor, Dept. of Civil Engineering, Dongkang College, 771 Duam-Dong, Bok-gu, Gwangju 500-714, South Korea.