Long-term continuous seismic monitoring of multi-span highway bridge and evaluation of bearing condition by wireless sensor network

A 45-month continuous seismic monitoring of a multi-span highway bridge by wireless sensor network (WSN) is described in this paper. The WSN monitoring system is developed using a simultaneous high-speed flooding technique and deployed to monitor a continuous 12-span 381.8 m long highway bridge in Katsuta city, Ibaraki prefecture, Japan. The WSN monitoring system consisted of 20 triaxial accelerometers placed on bridge girder, pier caps, abutment, and on the ground. The monitoring system has successfully recorded seismic responses of 63 earthquakes from August 2017 to December 2020. The paper describes the WSN monitoring system, analyses of seismic responses, and structural assessment using the recorded seismic responses. The analyses include inves-tigation on seismic response characteristics of girder, piers, and bearings, system identifications, and seismic performance evaluation of isolation bearings. The WSN monitoring system provides high quality of seismic re-sponses. Evaluations of ground motions recorded by WSN with the existing strong motion KNET seismograph network have demonstrated the accuracy, reliability, and robustness of WSN monitoring system. Using three system identification methods, dominant bridge modal parameters and their variations with respect to earth-quake levels were investigated. High-frequency filtering effect was utilized as indicator in assessment of isolation bearing performance. Systematic classification by clustering algorithm was conducted to determine whether the isolation bearings have functioned normally.