1. Assistant Professor, Dept. of Civil Engineering, Univ. of Chile, Avda. Blanco Encalada 2002, Santiago, Chile (corresponding author).
2. Associate Professor, Dept. of Civil and Environmental Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180.
3. Professor, Dept. of Civil and Environmental Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180.