1. Assistant Professor, Univ. of Connecticut, Storrs, CT 06066 (corresponding author).
2. Ph.D. Student, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801.
3. Nathan and Anne Newmark Endowed Professor in Civil Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801.