1. Research Assistant, Dept. of Civil and Environmental Engineering, 121 Porter Hall, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213 (corresponding author).
2. Research Assistant, Dept. of Civil and Environmental Engineering, 121 Porter Hall, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.
3. Professor, Dept. of Civil and Environmental Engineering, 123K Porter Hall, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.
4. Thomas Lord Professor and Head, Dept. of Civil and Environmental Engineering, 119D Porter Hall, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.
5. Professor, Dept. of Civil and Environmental Engineering, 123C Porter Hall, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.
6. Research Civil Engineer, Engineer Research and Development Center, Construction Engineer Research Laboratory, Champaign, IL 61826-9005.