1. Engineering Associate, RIZZO Associates, Inc., 500 Penn Center East, Suite 100, Pittsburgh, PA 15235.
2. Professor and the Fazlur R. Khan Endowed Chair of Structural Engineering and Architecture, Dept. of Civil and Environmental Engineering, ATLSS Engineering Research Center, Lehigh Univ., 117 ATLSS Dr., Bethlehem, PA 18015-4729 (corresponding author).