Collection of SHM Case Studies by ASCE SEI Methods of Monitoring Committee

Monitoring case study: 2nd Jindo Bridge

Jongwoong Park1, Soojin Cho2, Hyung-Jo Jung3, Jian Li4, Kirill Mechitov5, and Billie F. Spencer, Jr.6

1 Dept. of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, jongwoon@illinois.edu

2 University of Seoul, Seoul, South Korea, soojin@uos.ac.kr 3 Korean Advanced Institute of Science and Technology, Daejeon, South Korea, hjung@kaist.ac.kr

4 Dept. of Civil, Environmental, and Architectural Engineering, University of Kansas, Lawrence, KS, jianli@ku.edu 5 Dept. of Computer Science, University of Illinois at Urbana-Champaign., Urbana, IL, mechitov@illinois.edu

6 Dept. of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign., Urbana, IL, bfs@illinois.edu

ABSTRACT: This case study summarizes the deployment and operation of a large scale wireless smart sensor network for structural health monitoring of the 2nd Jindo Bridge, a cable-stayed bridge connecting Jindo Island with the Korean Peninsula. The wireless monitoring system, initially installed in 2009, had been expanded over a 3-year deployment to over 100 wireless sensor nodes providing more than 600 channels of sensor data, making it the world’s largest wireless network for bridge monitoring. This deployment has been extensively documented in the literature (Spencer et al., 2015; Rice et al., 2011; Jang et al., 2010).

Test Structure and Measured Data

Opening in 1984, the 1st Jindo Bridge is a cable-stayed bridge connecting the Korean peninsula and the Jindo Island; however, growing traffic demands quickly exceeded the load carrying capacity of the first bridge. The 2nd Jindo Bridge, which opened in 2005, is a streamlined steel box girder with a center span of 344 m supported by 60 parallel wire strand cables anchored to two diamond-shaped pylons. The bridge was to be instrumented with a continuous monitoring system that can autonomously estimate the various physical states of the bridge and serve as a testbed for evaluating wireless smart sensor network technology for structural health monitoring.

The objective of this deployment is long-term continuous monitoring of modal properties (natural frequencies, modal damping, and mode shapes), cable tension forces, and deck-cable interaction to determine structural performance.

The wireless monitoring system on the 2nd Jindo Bridge was initially installed in the summer of 2009. Seventy-one state-of-the-art wireless smart sensor (WSS) nodes with a total of 427 sensing channels were installed on the girder, the pylons, and the cables. Each node was comprised of the Imote2 processor board (including on-board CPU and radio transmitter), the ISM400 sensor board, and alkaline batteries. Measurements included 3-axes acceleration, plus temperature, humidity, and light. Combined with the ISHMP Services Toolsuite, these powerful nodes allow for synchronized data collection, aggregation, synthesis, and decision-making in real time.

The smart sensor nodes for the deck, pylons and cables were attached using different methods. The nodes were mounted to the steel deck and pylons using two magnets, each with a holding capacity of 10 kg, attached to the bottom of the enclosure. The nodes were mounted to the cables using two U-bolts and an aluminum mounting plate. These methods of mounting the sensors have proven to be fast, inexpensive, and secure.

Based on the success of the 2009 deployment, the monitoring system was extended to include 113 WSS nodes measuring a total of 659 channels of data in 2010 (see Figures 2), resulting in the world’s largest wireless smart sensor network for SHM. The ISM400 sensor board was used on 100 nodes. A new high-

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