1. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195-5502 (corresponding author).
2. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of Nevada, Reno, NV 89503.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195-5502.
4. Professor, Dept. of Civil and Environmental Engineering, Univ. of Nevada, Reno, NV 89503.