1. Assistant Professor, Departamento Ingeniería Civil, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2002, Santiago 8370449, Chile. E-mail: jmcphee@ing.uchile.cl
2. Distinguished Professor and Chair, Dept. of Civil and Environmental Engineering, Univ. of California, Los Angeles, CA 90095. E-mail: williamy@seas.ucla.edu