1. Assistant Professor, Dept. of Civil Engineering, Univ. of British Columbia, Vancouver, Canada V6T 1Z4 (corresponding author).
2. Research Assistant, Dept. of Civil Engineering, Univ. of British Columbia, Vancouver, Canada V6T 1Z4.
3. Emeritus Professor, Dept. of Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor, MI 48109-2125.