1. Professor, School of Civil Engineering, Purdue Univ., West Lafayette, IN 47907-1284.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Incheon National Univ., Incheon 406-772, South Korea; formerly, Ph.D. Research Associate, School of Civil Engineering, Purdue Univ., West Lafayette, IN 47907-1284 (corresponding author).