1. Graduate Student, Dept. of Civil, Environmental and Architectural Engineering, Univ. of Colorado at Boulder, 1111 Engineering Dr., UCB 428, Boulder, CO 80302.
2. Beavers Professor of Construction Engineering, Dept. of Civil, Environmental and Architectural Engineering, Univ. of Colorado at Boulder, 1111 Engineering Dr., UCB 428, Boulder, CO 80302 (corresponding author).
3. Professor, School of Civil and Construction Engineering, Oregon State Univ., 1500 SW Jefferson St., Corvallis, OR 97331.