1. Professor, School of Civil Engineering, Chongqing Univ., Chongqing 400045, P.R. China.
2. Ph.D. Candidate, School of Civil Engineering, Chongqing Univ., Chongqing 400045, P.R. China.
3. Professor, Dept. of Civil Engineering, Pennsylvania State Univ., Middletown, PA 17057.
4. Professor, School of Civil Engineering, Chongqing Univ., Chongqing 400045, P.R. China (corresponding author).
5. Ph.D. Candidate, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou 730000, P.R. China.