1. Prof., Dept. of Civ. and Struct. Engrg., Univ. of Hong Kong, Hong Kong
2. Sr. Lect., Dept. of Civ. and Struct. Engrg., Univ. of Hong Kong, Hong Kong
3. Res. Ofcr., Dept. of Civ. and Struct. Engrg., Univ. of Hong Kong, Hong Kong; on leave from Dept. of Mech., Zhongshan Univ., Guangzhou, People's Republic of China