1. Escuela de Ingeniería en Construcción, Pontificia Universidad Católica de Valparaíso, Chile.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Massachusetts, Amherst, MA 01003 (corresponding author).
3. Formerly, graduate student, Dept. of Civil and Environmental Engineering, Univ. of Massachusetts, Amherst, MA 01003.