1. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, 2350 Hayward St., Ann Arbor, MI 48109 (corresponding author).
2. Raymond Allen Jones Chair, School of Civil and Environmental Engineering, Georgia Institute of Technology, 790 Atlantic Dr. NW, Atlanta, GA 30332.
3. Associate Professor, Graduate School of Arts and Sciences, Univ. of Tokyo, 3-8-1 Komaba, Meguro-Ku, Tokyo 153-8902, Japan.