1. Post-Doctoral Fellow, Dept. of Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2125.
2. Ph.D. Student, Dept. of Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2125.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2125 (corresponding author).