1. Assoc. Prof. of Civ. Engrg., Massachusetts Inst. of Tech., Cambridge, Mass.
2. Prof. of Civ. Engrg. and Head of Structures Div., Dept. of Civ. Engrg., Massachusetts Inst. of Tech., Cambridge, Mass.
3. Prof. of Civ. Engrg., Universidad de Chile, Santiago, Chile.