1. Member of Chinese Concrete Structure Standard Committee, Professor, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, P.R. China.
2. Vice-Director, National Engineering Technical Technique Research Center of Industrial Building, Beijing 100088. P.R. China.
3. Graduate Student, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, P.R. China.