Doctor of Philosophy (PhD)
Civil and Environmental Engineering
Stay cables are vulnerable to dynamic excitations because of their low intrinsic damping. Excessive cable vibrations cause frequent maintenance and are detrimental to the safety of the entire bridge. Targeting the severe cable vibration problem, in addition to using the existing Magnetorheological (MR) damper, the current study proposes a new type of damper, called the Tuned Mass Damper-Magnetorheological (TMD-MR) damper. Theoretical and experimental investigations for the damper performance on the cable vibration reduction are conducted, which provides the necessary research support for practical implementation. Experiments on the individual MR damper are carried out first to gain some experience on the damper itself. The MR damper is then added to the cable to demonstrate its effectiveness for vibration reduction, both passively and semiactively. Based on the obtained information, a TMD-MR damper is manufactured according to the vibration level of the experimental cable. The designed TMD-MR damper is then added to the experimental cable, and possible factors that may affect the damper performance are investigated experimentally. To get a profound and extended understanding of the TMD-MR damper performance, a simple horizontal taut cable-damper model, and then a more refined analytical model for the inclined sagged cable-TMD-MR system, are established. Through a parametric study on the achieved modal damping of the system, a thorough investigation on the effect of the cable or the damper parameters on the TMD-MR damper performance is carried out. The design process of the damper for the rain-wind induced cable vibration reduction is also explained based on the parametric study. Though this study focuses on the research of the proposed TMD-MR damper, the viscous damper is also considered for comparison purposes. The present research demonstrates not only that semiactive control is more efficient than the passive control, but also that MR dampers are failure-free devices for vibration control since their passive mode provides damping too. The proposed TMD-MR damper combines the flexibility of the TMD damper and the adjustability of the MR damper, and therefore is a promising way to reduce the cable vibration, though further research is necessary to warrant field applications.
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Wu, Wenjie, "Theoretical and experimental study on cable vibration reduction with a TMD-MR damper" (2006). LSU Doctoral Dissertations. 1430.
Steve C.S. Cai