1. Assistant Professor, Dept. of Construction Management, Univ. of Washington, Seattle, WA 98195.
2. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801 (corresponding author).
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801.