1. Postdoctoral Researcher, Dept. of Civil and Environment Engineering and Geodetic Science, Ohio State Univ., 470 Hitchcock Hall, 2070 Neil Ave., Columbus, OH 43210-1275 (corresponding author).
2. Systems Scientist, Robotics Institute (RI), Newell-Simon Hall, Carnegie Mellon Univ., Pittsburgh, PA 15213.
3. Professor, Dept. of Civil and Environmental Engineering, Carnegie Mellon Univ., Pittsburgh, PA 15213.