1. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195 (corresponding author).
2. Structural Engineer, Degenkolb, Seattle, WA 98101.
3. Structural Engineer, KPFF Consulting Engineers, Seattle, WA 98101.
4. Structural Engineer, Simpson Gumpertz & Heger, Waltham, MA 02453.
5. Professor, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195.
6. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195.