1. Postdoctoral Research Fellow, Dept. of Civil and Environmental Engineering, Univ. of Connecticut, 261 Glenbrook Rd., Unit 2037, Storrs, CT 06269 (corresponding author).
2. Former Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, 205 North Mathews, Urbana, IL 61801.
3. William J. and Elaine F. Hall Endowed Professor in Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, 205 North Mathews, Urbana, IL 61801.