1. Assistant Professor, Dept. of Civil Engineering, Hankyong National Univ., 327, Chungang-ro, Anseong-si, Gyeonggi-do, 456-749, Korea; formerly, Research Fellow of Gyeonggi Research Institute.
2. Professor, Dept. of Civil and Environmental Engineering, Seoul National Univ., San 56-1, Shinlim-dong, Gwanak-gu, Seoul, 151-742, Korea (corresponding author).