1. Professor, Dept. of Civil Engineering, Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry, Tsinghua Univ., Beijing 100084, China (corresponding author).
2. Associate Professor, Dept. of Civil Engineering, Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry, Tsinghua Univ., Beijing 100084, China.
3. Ph.D. Candidate, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, China.