1. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of Pittsburgh, Pittsburgh, PA 15261 (corresponding author).
2. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of Pittsburgh, Pittsburgh, PA 15261.
3. Professor, Dept. of Civil and Environmental Engineering, Carnegie Mellon Univ., Pittsburgh, PA 15213.
4. Professor, Dept. of Civil and Environmental Engineering, Univ. of Pittsburgh, Pittsburgh, PA 15261.