VIBRATION MITIGATION OF LONG STAY CABLE USING DAMPERS AND CROSS-TIES
The span of cable-stayed bridges has increased to more than 1000 meters, such as Sutong Bridge located in Jiangsu of China and Stonecuter Bridge in Hong Kong, both are under contruction. The longest stay cable for such large span bridges reaches to about 600 meters. Long stay cables are very senstive to circumstance excitation, such as wind, wind-rain or traffic loads, due to their low inherent damping. Wing-induced or wind-rain-induced vibrations are an important issue expecially. As countermeasures of cable vibration mitigation, mechanical damper, cross-ties or aerodynamic means are often adoped. A mechanical damper is usually installed near the anchorage of a stay cable in transversal direction to increase the modal damping of the cable. Cable cross-ties connect the stay cables together to increase the stiffness and the damping of the cable system. Besides of the effectiveness of mitigating wind-induced vibration, the cross-ties can increase the natural frequency of the cable system so the internal resonance and parameter vibrations can be avoided. An aerodynamic means modifies the surface condition of stay cable and is effective especially for suppressing the wind-rain-induced vibrations. This paper focuses on the vibration mitigation countermeasures using mechanical damper and cross-ties. A full scale experiment of cable with various types of mechanical dampers was conducted. The effects of damper nonlinearity and stiffness were investigated. The comparison of analytical damping calculated from nonlinear theory and equivalent linear theory to that obtained from experiment was conducted. Parametric studies on cross-ties were carried out by numerical simulations.
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