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Smart Structures and Systems
  Volume 15, Number 3, March 2015 , pages 523-541

Effects of local structural damage in a steel truss bridge on internal dynamic coupling and modal damping
Hiroki Yamaguchi, Yasunao Matsumoto and Tsutomu Yoshioka

    Structural health monitoring of steel truss bridge based on changes in modal properties was investigated in this study. Vibration measurements with five sensors were conducted at an existing Warren truss bridge with partial fractures in diagonal members before and after an emergency repair work. Modal properties identified by the Eigensystem Realization Algorithm showed evidences of increases in modal damping due to the damage in diagonal member. In order to understand the dynamic behavior of the bridge and possible mechanism of those increases in modal damping, theoretical modal analysis was conducted with three dimensional frame models. It was found that vibrations of the main truss could be coupled internally with local vibrations of diagonal members and the degree of coupling could change with structural changes in diagonal members. Additional vibration measurements with fifteen sensors were then conducted so as to understand the consistency of those theoretical findings with the actual dynamic behavior. Modal properties experimentally identified showed that the damping change caused by the damage in diagonal member described above could have occurred in a diagonal coupled mode. The results in this study imply that damages in diagonal members could be detected from changes in modal damping of diagonal-coupled modes.
Key Words
    structural health monitoring; truss bridge; vibration measurement; ERA; diagonal member-coupled vibration; modal damping; damage detection
Hiroki Yamaguchi and Yasunao Matsumoto: Department of Civil and Environmental Engineering, Saitama University
255 Shimo-Ohkubo, Sakura, Saitama 338-8570, Japan
Tsutomu Yoshioka: Nippon Engineering Consultants Co., Ltd, 3-23-1, Komagome, Toshima, Tokyo 170-0003, Japan

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