抗风缆风构和中央扣对上松坪桥动力特性的影响

Effect of wind cable wind bracing structures and center ties on dynamic property of Shangsongping Bridge

采用有限元建模分析了抗风缆、中央扣和风构对主跨266m的上松坪桥动力特性的影响.比较了具有不同初应变的抗风缆对结构基频的影响,抗风缆初应变越大,其提供势能占总势能比重也越大,对基频影响也相应增大,设置菱形风构对结构对称和反对称竖弯频率的影响很小,对扭转频率的提高较为明显,通过设置单联柔性中央扣、三联柔性中央扣以及三联刚性中央扣情况下结构的动力特性.结果表明:中央扣的设置对于正对称和反对称竖弯频率以及正对称扭转频率的影响甚微,反对称扭转基频可较大提高,且中央扣刚度是影响反对称扭转基频的重要因素,设置刚性中央扣不仅频率得到提高,反对称扭转振型也相应改变,合理地选择抗风措施以及相应措施的参数可以显著提高钢桁架加劲梁悬索桥的气动稳定性.

Finite element models are built to analyze the effect of wind cable,wind bracing structures and center ties on Shangsongping Bridge which is a suspension bridge with main span of 266 m.Several wind cables with different initial strains are adopt in the bridge model,and their effects on dynamic property are compared.The greater the initial strain of the wind cable,the bigger the stiffness of the structure.As a result,the fundamental frequencies of the bridge get higher.The wind bracing structures have little effect on the vertical frequencies,while they can increase the torsional frequencies effectively.The dynamic property results of the bridge setting single-span and three-span flexible center ties and single-span rigid center ties are obtained.The results show that the center ties have almost no effect on symmetrical and anti-symmetrical vertical frequencies as well as symmetrical torsional frequency.They can increase the frequency of anti-symmetrical torsional frequency to some extent.The stiffness of the center ties is the major influence factor of anti-symmetrical torsional frequency.The rigid center ties not only increase frequency of that model,but also change the shape of the corresponding mode of vibration.Selecting reasonable wind-resistant measures and optimizing parameters of these aerodynamic measures can obviously increase the aerodynamic stability of the bridge.