Monitoring and Structural Assessment of Instrumented Cable-Stayed Bridges Using Recorded Seismic Responses

This paper describes case studies and lessons learned on seismic monitoring and structural assessment of several cable-stayed bridges using seismic records from wired and wireless monitoring system. The subject bridges are Yokohama-Bay bridge, Tokachi bridge and Shin-Nakagawa bridge in Japan. At the Yokohama-Bay bridge (total length 860 m, main span 460 m), a comprehensive wired monitoring system has been established for more than 30 years. Records from various levels of earthquakes including the largest one in Tohoku 2011 were studied to understand characteristics of seismic responses and explain structural behaviors such as tower-girder sliding and pounding. At the Tokachi bridge (total length 501 m, main span 251), a single-plane cable-stayed bridge, behaviors of friction bearings were investigated using recorded seismic responses from wired monitoring system and system identification was implemented to explain bearing behaviors under various earthquake levels. At the Shin-Nakagawa bridge (total length 533 m, main span 283 m), the development of wireless sensor network (WSN) and the results of 45-month continuous seismic monitoring campaign are described. The WSN monitoring system successfully recorded high quality seismic responses from 63 seismic events which included near-field and far-field earthquakes. Important analyses on the seismic records and performance of LRB seismic isolation bearing, using the recorded seismic responses are presented.