1. Private Consultant and formerly National Science Foundation Graduate Research Fellow, School of Civil and Environmental Engineering, Cornell Univ., Hollister Hall, Ithaca, NY 14853.
2. Professor, School of Civil and Environmental Engineering, Cornell Univ., 273 Hollister Hall, Ithaca, NY 14853.
3. Lecturer and Research Associate, School of Civil and Environmental Engineering, Cornell Univ., Hollister Hall, Ithaca, NY 14853 (corresponding author).