1. Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2125 (corresponding author).
2. Ph.D. Candidate, Dept. of Mechanical and Civil Engineering, California Institute of Technology, Pasadena, CA 91125.
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2125.