1. Prof., Dept. of Civ. and Geological Engrg., Princeton Univ., Princeton, N.J.
2. Research Assoc., Dept. of Civ. Engrg. and Engrg. Mechanics, Columbia Univ., New York, N.Y.
3. Grad. Student, Dept. of Civ. and Geological Engrg., Princeton Univ., Princeton, N.J.