1. Ph.D. Candidate, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., New York, NY 10027. E-mail: nc2112@columbia.edu
2. Assistant Professor, School of Construction, Virginia Tech, Blacksburg, VA 24061-0105 (corresponding author). E-mail: garvin@jvt.edu.
3. Assistant Professor, Dept. of Statistics, Columbia Univ., New York, NY 10027. E-mail: vecer@stat.columbia.edu