1. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of South Carolina, 300 Main St., Columbia, SC 29208.
2. Distinguished Professor, Dept. of Civil and Environmental Engineering, Univ. of South Carolina, 300 Main St., Columbia, SC 29208 (corresponding author).
3. Mr. and Mrs. Irwin B. Kahn Professor, Dept. of Civil and Environmental Engineering, Univ. of South Carolina, 300 Main St., Columbia, SC 29208.