1. Postdoctoral Researcher, Computer Science Laboratory, École Polytechnique, 91120 Palaiseau, France.
2. Assistant Professor, Dept. of Civil, Construction, and Environmental Engineering, North Carolina State Univ., Raleigh, NC 27695 (corresponding author).
3. Beavers Endowed Associate Professor, Dept. of Civil, Environmental, and Architectural Engineering, Univ. of Colorado Boulder, Boulder, CO 80309.