1. Associate Professor, School of Civil Engineering, 2nd Campus of Harbin Institute of Technology, P.O. Box 2546, No. 202 Haihe Rd., Harbin 150090, P.R. China.
2. Professor, School of Civil and Hydraulic Engineering, Dalian Univ. of Technology and School of Civil Engineering, Harbin Institute of Technology, No. 2 Linggong Rd., Dalian 116024, P.R. China (corresponding author).