1. Professor, College of Civil and Transportation Engineering, Hohai Univ., Nanjing, Jiangsu 210098, P.R. China.
2. Research Assistant, College of Civil and Transportation Engineering, Hohai Univ., Nanjing, Jiangsu 210098, P.R. China (corresponding author).
3. Research Assistant, College of Civil and Transportation Engineering, Hohai Univ., Nanjing, Jiangsu 210098, P.R. China.