1. Research Institute of Structural Engineering and Disaster Reduction; College of Civil Engineering, Tongji University; Shanghai 200092 China
2. College of Civil Engineering and Architecture; Zhejiang University; Hangzhou 310058 China
3. Department of Civil and Environmental Engineering; University of Illinois at Urbana-Champaign; Urbana Illinois 61801 USA
4. State Key Laboratory of Disaster Reduction in Civil Engineering; Tongji University; Shanghai 200092 China