1. Ph.D. Graduate, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523-1372.
2. Professor, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523-1372 (corresponding author).
3. Professor, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523-1372.