1. Ph.D. Candidate, Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801.
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801 (corresponding author).
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana Champaign, Urbana, IL 61801.