1. Lecturer, Dept. of Civil Engineering, Tianjin Univ., Tianjin 300072, P.R. China (corresponding author).
2. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Macau, Macao SAR, P.R. China.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Macau, Macao SAR, P.R. China.