1. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana–Champaign, 205 N. Mathews Ave., Urbana, IL 61801.
2. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana–Champaign, 205 N. Mathews Ave., Urbana, IL 61801 (corresponding author).