1. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, 2350 Hayward St., Ann Arbor, MI 48109 (corresponding author).
2. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of Michigan, 2350 Hayward St., Ann Arbor, MI 48109.
3. Professor Emeritus, Dept. of Civil and Environmental Engineering, Univ. of Michigan, 2350 Hayward St., Ann Arbor, MI 48109.
4. Professor, Dept. of Civil, Architectural and Environmental Engineering, Univ. of Texas at Austin, 301 E. Dean Keeton St., Austin, TX 78712.