1. McCormick Institute Professor and W. P. Murphy Professor of Civil Engineering and Materials Science, Northwestern Univ., 2145 Sheridan Road, CEE/A135, Evanston, IL 60208 (corresponding author).
2. Assistant Professor, Dept. of Civil Engineering, Univ. of Pittsburgh, PA; formerly, Postdoctoral Research Associate, Northwestern Univ., Evanston, IL 60208.
3. Graduate Research Assistant, Northwestern Univ., Evanston, IL 60208.