1. School of Civil Engineering, Central South University, Changsha, Hunan 410075, China.
2. Key Laboratory of Engineering Structure of Heavy Railway (Central South University), Ministry of Education, Changsha, Hunan 410075, China.
3. Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia.
4. Department of Civil Engineering, University of Kentucky, Lexington, KY 40506-0281, USA.