1. Key Laboratory of C & PC Structures of Ministry of Education, National Prestress Engineering Research Center, Southeast University, Nanjing 211189, P. R. China
2. College of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, P. R. China
3. Qian Xuesen Laboratory of Space Technology, Beijing 100094, P. R. China
4. School of Civil Engineering, Southeast University, Nanjing 211189, P. R. China