1. Prager Professor, Dept. of Structural Engineering, Univ. of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (corresponding author).
2. Kimball Assistant Professor, Dept. of Civil and Environmental Engineering, Pennsylvania State Univ., University Park, PA 16802.
3. Assistant Professor, Dept. of Civil and Materials Engineering, Univ. of Illinois at Chicago, 842 W. Taylor St., Chicago, IL 60607.