1. Chair Professor, College of Civil Engineering, Hunan Univ., Changsha 410082, P.R. China (corresponding author).
2. Ph.D. Candidate, College of Civil Engineering, Hunan Univ., Changsha 410082, P.R. China.
3. Graduate Research Assistant, College of Civil Engineering, Hunan Univ., Changsha 410082, P.R. China.
4. Professor, Magnel Laboratory for Concrete Research, Dept. of Structural Engineering, Ghent Univ., B-9052 Ghent, Belgium.