1. Senior Engineer, Central Research Institute, Samsung Heavy Industries Co., Ltd., 80 Jangpyeong 3ro, Geoje Si, Gyeonsangnam Do 656-710, Korea.
2. Professor, Dept. of Civil Engineering, Seoul National Univ., San 56-1, Shinlim-Dong, Kwanak-Ku, Seoul 151-742, Korea.
3. Associate Professor and Vice Chair, Dept. of Civil and Environmental Engineering, Univ. of California, Los Angeles, 5731 Boelter Hall, Los Angeles, CA 90095-1593 (corresponding author).