1. Geostructural Engineer, McPhail Associates, Cambridge, MA 02144 (corresponding author).
2. Dept. of Civil Engineering, City College of CUNY, New York, NY 10031.
3. Dept. of Civil & Environmental Engineering, Tufts Univ., Medford, MA 02155.
4. Federal Highway Administration, Office of Infrastructure, R&D, McLean, VA 22101.