1. Research Fellow, School of Civil and Environmental Engineering, Nanyang Technological Univ., 50 Nanyang Ave., Singapore 639798; formerly, Dept. of Civil Engineering, Univ. of Hong Kong, Pokfulam Rd., Hong Kong, China (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Hong Kong Polytechnic Univ., Hung Hom, Hong Kong, China; formerly, Dept. of Civil Engineering, Univ. of Hong Kong, Pokfulam Rd., Hong Kong, China.