1. Assistant Professor, Dept. of Structural Engineering, Politecnico di Milano, Piazza Leonardo da Vinci, 20133 Milano, Italy (corresponding author). E-mail: liberato.ferrara@polimi.it
2. Associate Professor, Faculty of Architecture and Civil Engineering, Daegu Haany Univ., Yugok 290, Gyeongsan, Gyeongbuk 712-715, South Korea. E-mail: ydpark@dhu.ac.kr
3. Walter P. Murphy Professor of Civil Engineering, Director of ACBM, Northwestern Univ., 2145 Sheridan Rd., Evanston, IL 60208. E-mail: s-shah@northwestern.edu