1. University Fellow, Dept. of Civil & Environmental Engineering, 1 Univ. Plaza, Univ. of Wisconsin-Platteville, Platteville, WI 53818-3099; formerly, Graduate Research Assistant, Dept. of Civil and Environmental Engineering, 1372 Campus Delivery, Colorado State Univ., Fort Collins, CO 80523-1372.
2. Professor, Dept. of Civil and Environmental Engineering, 1372 Campus Delivery, Colorado State Univ., Fort Collins, CO 80523-1372 (corresponding author).