1. Ph.D. Candidate, Dept. of Civil, Architectural and Environmental Engineering, Missouri Univ. of Science and Technology, Rolla, MO 65409; formerly, Research Assistant, Tsinghua Univ., Beijing 100084, China.
2. Professor, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, China.
3. Professor, Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast Univ., Nanjing 210096, China (corresponding author).