1. Research Associate, Dept. of Civil and Environmental Engineering, Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, P.R. China (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, P.R. China.
3. Senior Lecturer, Dept. of Civil and Natural Resources Engineering, Univ. of Canterbury, Private Bag 4800 Christchurch, New Zealand.