1. Assistant Professor, Dept. of Civil and Environmental Engineering, Utah State Univ., Box 4110, Logan, UT 84322.
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of Washington, Box 352700, Seattle, WA 98195.
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Washington, Box 352700, Seattle, WA 98195.