Implementation of Wireless Sensor Network for Continuous Seismic Monitoring of Isolated Cable-Stayed Bridge

Abstract

The deployment of wireless sensor network (WSN) for continuous seismic monitoring system of cable-stayed bridge is presented in this paper. A newly developed WSN that is based on simultaneous high-speed concurrent transmission flooding technique was implemented on the Shin-Nakagawa Bridge, a 530-m single-plane, single-pylon, steel box girder, cable-stayed bridge in Ibaraki prefecture, eastern Japan. The structure is seismically isolated with laminated rubber bearings at the main pylon and piers. Some isolation bearings were partially damaged by the 2011 Great East Japan (Tohoku) earthquake. As a part of monitoring, a WSN with a total of 26 sensor nodes were installed at several locations on the piers, main pylon, girder, and ground. This paper describes the WSN system, the monitoring scheme and procedure, analysis of recorded seismic responses, and their use for structural assessment, especially the performance of isolation bearings during earthquakes. The monitoring system successfully recorded structural responses from 63 earthquakes in the 45 months monitoring period between August 2017 to December 2020, which include the responses from near-field and far-field earthquakes. The comparisons of recorded ground motions with existing nearby seismograph have shown the accuracy and reliability of the WSN. Modal parameters of the bridge were successfully determined from the seismic responses obtained from the WSN using multi-input multi-output time-domain system identifications. Characteristics of seismically isolated bridge responses, such as high-frequency filtering effect and decoupling effect of the girder responses, can be clearly observed from the records of the large earthquakes.