1. Mem. ASME Key Laboratory of C & PC Structures of Ministry of Education, National Prestress Engineering Research Center, Southeast University, Si Pai Lou 2#, Nanjing 210096, China e-mails: ;
2. School of Civil Engineering, Southeast University, Nanjing 210096, China e-mail:
3. Department of Civil Engineering, Strathclyde University, Glasgow G12 8QQ, UK e-mail: