1. McCormick Institute Professor and W.P. Murphy Professor of Civil and Mechanical Engineering and Materials Science, Dept. of Civil and Environmental Engineering, Northwestern Univ., 2145 Sheridan Rd., CEE/A135, Evanston, IL 60208 (corresponding author).
2. Postdoctoral Researcher, Dept. of Civil and Environmental Engineering, Northwestern Univ., 2145 Sheridan Rd., Evanston, IL 60208; mailing address: 345 Brook St., Providence, RI 02912.