1. Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Lehigh Univ., Bethlehem, PA 18015-3094.
2. P.C. Rossin Professor, Dept. of Civil and Environmental Engineering, Lehigh Univ., Bethlehem, PA 18015-3094 (corresponding author).
3. Robert Bolles and Yasuko Endo Professor, Dept. of Applied Mathematics, Univ. of Washington, Seattle, WA 98195-3925.