1. Res. Fellow, School of Civ. and Struct. Engrg., Nanyang Technol. Univ., Nanyang Ave., Singapore 639798.
2. Assoc. Prof., School of Civ. and Struct. Engrg., Nanyang Technol. Univ., Nanyang Ave., Singapore 639798.
3. Bechtel System and Infrastructure Inc., San Francisco, CA, and Consulting Prof., Stanford University, Stanford, CA 94305.