1. Graduate Student, Research Assistant, Dept. of Civil & Environmental Engineering, Tufts Univ., Medford, MA 02155.
2. Professor, Dept. of Civil & Environmental Engineering, Tufts Univ., Medford, MA 02155 (corresponding author).
3. Professor of the Practice, Dept. of Civil & Environmental Engineering, Tufts Univ., Medford, MA 02155.