Study on Suspension Type Bridges Multi-Strand Cable with Economical and Aerodynamic Performances

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The present study aims at the development of multi-strand cable for a long suspension type bridge from viewpoint of both economical and aerodynamic performances. Stay cables of cable-stayed bridges and hanger cables of suspension bridges are known to have various types of vibration under wind action. In order to suppress the aerodynamic vibrations, many researches have been conducted. In the present study, multi-strand cable with helical wire is proposed from viewpoint of aerodynamic stability and of cost performance of manufacture, transportation and erection. The multi-strand cable is composed of small strands, therefore adding to the manufacturing small strands in the factory, small capacity is needed for transportation and erection devices regardless of required cable capacity. The outer shape of the multi-strand cable is uneven and the shape gives good performance to suppress the aerodynamic vibrations such as vortex-excited vibration and rain-wind-induced vibration. The experiments were conducted in the wind tunnel with test section 1780 x 790 mm of Kyshu Institute of Technology. The models used in the experiments were rigid models made by the aluminum pipe. And the model was elastically supported in heaving motion by four coil-springs. The observation of response and measuring surface pressure were conducted. It was clarified by measuring surface pressure of the cable that the multi-strand cable with helical wire can suppress the various aerodynamic vibrations. The mechanism of suppressing aerodynamic vibrations is seemed that the gap between grooves on multi-strand and helical wire makes the surface pressure appropriately smooth for suppressing vibrations.