1. Ph.D. Candidate, Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, China.
2. Research Assistant Professor, Ulsan National Institute of Science and Technology, Ulsan 689-798, Republic of Korea.
3. Nathan M. and Anne M. Newmark Endowed Chair in Civil Engineering, Dept. of Civil and Environmental Engineering, Univ. of Illinois, Urbana, IL 61801.
4. Professor, Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, China (corresponding author).