1. Graduate Research Assistant, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 610 Seeley W. Mudd 500 West 120th St., New York, NY 10027.
2. Postdoctoral Research Associate, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 610 Seeley W. Mudd 500 West 120th St., New York, NY 10027.
3. Associate Research Scientist, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 610 Seeley W. Mudd 500 West 120th St., New York, NY 10027.
4. Associate Professor, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 610 Seeley W. Mudd 500 West 120th St., New York, NY 10027 (corresponding author).