1. Research Professor, Korea Advanced Institute of Science and Technology, Dept. of Civil and Environmental Engineering, 291 Daehak-ro, Yuseong-gu, Daejeon 130-743, Republic of Korea (corresponding author).
2. Assistant Professor, South Dakota Univ., Dept. of Civil and Environmental Engineering, 148 Crothers Engineering Hall, Brookings, SD 57007.
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin-Madison, 1204 Engineering Hall, 1405 Engineering Dr., Madison, WI 53706.