1. School of Science, Qingdao Univ. of Technology, Fushun Rd. No. 11, Qingdao, Shandong 266033, PR China.
2. Professor, School of Civil Engineering, Chongqing Univ., Shabei Rd. No. 83, Chongqing 400045, PR China.
3. Professor, College of Civil and Transportation Engineering, Hohai Univ., Xikang Rd. No. 1, Nanjing, Jiangsu 210098, PR China (corresponding author).
4. Chair Professor, Dept. of Civil and Environmental Engineering, Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.