1. School of Civil Engineering, Tsinghua University , Beijing 100084, China
2. Department of Civil and Earth Resources Engineering, Kyoto University , Kyoto 615-8530, Japan
3. Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology , Beijing 100124, China
4. Chair for Reliability Engineering, TU Dortmund University , Leonhard-Euler-Straße 5, Dortmund 44227, Germany