Developmental Study on Dynamically Stable Cable Systems

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A crossing rope system has been applied to stay cable in cable-stayd bridges in order to control their wind-induced vibrations. In case of suspension bridges, on the other hand, a new cable system without storm rope has been studied to simplify the catwalk system for main-cable erection. The main objective of this study is, therefore, to investigate the possibility of developing new cable system which is dynamically stable. The results obtained from the study are summarized as follows.1.The modal damping of cable system in cable-stayd bridges was evaluated by model experiment and numerical analysis. The damping effect of the crossing rope system is mainly clarified.2.The analytical method for the damping evaluation based on the energy representation of modal damping was proposed and applied to three different types of long-spanned cable-stayd bridges ; Ikuchi Bridge with composite box-girders, Yokohama Bay Bridge with truss girder and Tsurumi Tsubasa Bridge with the stay-cable system in single plane. The modal damping ratios for different modes of each bridge were evaluated and compared with the field-measured values. The high potential of the analytical evaluation of the damping characteristics was shown through these damping analyzes. The relation between modal damping of cable-stayd bridge and its cable system was also discussed.3.The dynamic characteristics of catwalk system was investigated by a series of experiments with simplified models. Not only the modal damping of the cable system in the linear response but also the effect of nonlinear behavior on the dynamic stability of the system were measured in the experiment.