1. Associate Professor, College of Civil Engineering, Xiangtan Univ., Xiangtan 411105, China.
2. Graduate Student, College of Civil Engineering, Xiangtan Univ., Xiangtan 411105, China.
3. Professor, College of Civil Engineering, Xiangtan Univ., Xiangtan 411105, China.
4. Professor, School of Civil Engineering, Changsha Univ. of Science and Technology, Changsha 410114, China (corresponding author).