1. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, 2108 Newmark Civil Engineering Laboratory, 205 North Mathews Ave., Urbana, IL 61801. E-mail: fhnstck@uiuc.edu
2. Bruce G. Johnston Professor of Structural Engineering, Dept. of Civil and Environmental Engineering, Lehigh Univ., 117 ATLSS Dr., Bethlehem, PA 18015. E-mail: jmr5@lehigh.edu
3. Joseph T. Stuart Professor of Structural Engineering, Dept. of Civil and Environmental Engineering, Lehigh Univ., 117 ATLSS Dr., Bethlehem, PA 18015. E-mail: rs0c@lehigh.edu