1. Member, ASCE
2. Assoc. Prof., Pontificia Universidad Católica de Chile, Casilla 306, Correo 22, Santiago, Chile.
3. Johnson Professor, Dept. of Civ. Engrg., Univ. of California, Berkeley, CA 94720.
4. PhD Student, Pontificia Universidad Católica de Chile, Casilla 306, Correo 22, Santiago, Chile.