1. Research Assistant, School of Civil Engineering, Purdue Univ., West Lafayette, IN 47906.
2. Associate Professor, School of Civil Engineering, Purdue Univ., West Lafayette, IN 47906 (corresponding author).
3. Research Assistant, Dept. of Civil and Environmental Engineering, Michigan State Univ., East Lansing, MI 48823.
4. Professor, Dept. of Civil and Environmental Engineering, Michigan State Univ., East Lansing, MI 48823.