1. Ph.D. Student, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195.
2. Postdoc Researcher, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195 (corresponding author).