1. Member, ASCE
2. Assoc. Prof., Dept. of Civ. Engrg. and Engrg. Mech., Columbia Univ., 500 West 120th St., New York, NY 10027. E-mail: ling@civil.columbia.edu
3. Res. Asst., Dept. of Civ. and Envir. Engrg., University of Delaware, Newark, DE 19711; currently, Visiting Scholar, Dept. of Civ. Engrg. and Engrg. Mech., Columbia Univ., New York, NY 10027.