1. Assistant Professor, Dept. of Civil Engineering, Univ. de Chile. Ave. Blanco Encalada 2002, Piso 4, Santiago, Chile. E-mail: riherrer@ing.uchile.cl
2. Bruce G. Johnston Professor of Structural Engineering, ATLSS Center, Dept. of Civil and Environmental Engineering, Lehigh Univ., 117 ATLSS Dr., Bethlehem, PA 18015 (corresponding author). E-mail: jricles@lehigh.edu
3. Joseph T. Stuart Professor of Structural Engineering, ATLSS Center, Dept. of Civil and Environmental Engineering, Lehigh Univ., 117 ATLSS Dr., Bethlehem, PA 18015. E-mail: rsause@lehigh.edu