1. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of Michigan, 2340 G. G. Brown Building, Ann Arbor, MI 48109.
2. Assistant Professor, Dept. of Civil, Construction, and Environmental Engineering, North Carolina State Univ., Campus Box 7908, 431C Mann Hall, Raleigh, NC 27695; formerly, Graduate Research Assistant, Purdue Univ., School of Civil Engineering, 550 Stadium Mall Dr., West Lafayette, IN 47907.
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, 2340 G. G. Brown Building, Ann Arbor, MI 48109.
4. Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, 2340 G. G. Brown Building, Ann Arbor, MI 48109 (corresponding author).