1. Graduate Student, Dept. of Civil and Environmental Engineering, Cornell Univ., Hollister Hall, Ithaca, NY 14853-3501 (corresponding author).
2. Senior Lecturer, Dept. of Civil and Environmental Engineering, Cornell Univ., Hollister Hall, Ithaca, NY 14853-3501.
3. Professor, Dept. of Civil and Environmental Engineering, Cornell Univ., Hollister Hall, Ithaca, NY 14853-3501.