1. Assistant Professor, Dept. of Civil Engineering and Applied Mechanics, Columbia Univ., 610 SW Mudd, Mail Code: 4709, New York, NY 10027 (corresponding author).
2. Graduate Student, Dept. of Civil Engineering and Applied Mechanics, Columbia Univ., 610 SW Mudd, Mail Code: 4709, New York, NY 10027.
3. Professor, Dept. of Civil Engineering and Applied Mechanics, Columbia Univ., 610 SW Mudd, Mail Code: 4709, New York, NY 10027.
4. Professor, Dept. of Applied Physics and Applied Mathematics, Columbia Univ., 1120 SW Mudd, Mail Code: 4701, New York, NY 10027.