1. Professor and Distinguished Teacher, Dept. of Civil and Environmental Engineering, Southern Illinois Univ., Carbondale, IL 62901.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Southern Illinois Univ., Carbondale, IL 62901 (corresponding author).
3. Former Graduate Student, Dept. of Civil and Environmental Engineering, Southern Illinois Univ., Carbondale, IL 62901.
4. Professor, Dept. of Physics, Univ. of Memphis, Memphis, TN 38152.