1. College of Civil Engineering, Hunan University, Yuelushan, Changsha, Hunan 410082, P. R. China
2. Key Laboratory for Wind and Bridge, Engineering of Hunan Province, Changsha 410082, Hunan, P. R. China
3. Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Hum, Hong Kong, P. R. China