1. Research Associate, Dept. of Civil Engineering, Univ. of Hong Kong, Hong Kong, P. R. China.
2. Research Assistant Professor, Dept. of Civil and Environmental Engineering, Hong Kong Polytechnic Univ., Hung Hom, Kowloon, Hong Kong, P. R. China.
3. Professor, Dept. of Civil Engineering, Univ. of Hong Kong, Hong Kong, P. R. China (corresponding author).