大跨斜拉桥桥面风致抖振的粘滞阻尼控制分析

Lateral buffeting control of long-span cable-stayed bridge deck by viscous dampers

现代大跨度斜拉桥结构重量轻、阻尼小,因而对风的作用比较敏感。紊流风诱发桥梁过大的抖振响应会危及行车、行人的舒适和安全。本文利用有限元软件ANSYS,以山东滨州黄河公路大桥为例建立了大跨斜拉桥三维空间有限元模型,在全桥动力特性分析的基础上,利用混合自回归模型模拟桥梁脉动风荷载,并进行了自激力的时域化处理,重点分析了桥面侧向抖振响应;通过对粘滞阻尼器力学特性的分析,提出了在桥塔和主梁之间安装与桥面成45°的粘滞阻尼器来控制桥面侧向抖振响应的方案,并分析了不同阻尼系数时的控制效率。研究结果表明:在侧向风力的强迫作用下,桥面侧向抖振响应不可忽视;粘滞阻尼器控制下,桥面抖振响应显著减小,各主要构件内力均无明显增加,且随着阻尼系数的增大,减振效率显著增大,阻尼器的出力也增大,但当阻尼系数达到一定值后,减振效率的增大趋于平缓,存在一个经济合理的最优值。

In recent years, the wind effects on bridges become more prominent as the structures are with longer span, more flexibility and less damping. The excessive amplitude of buffeting vibration may also make the passing cars and pedestrians uncomfortable or unsafe. In this paper, the finite element model of Binzhou Yellow River Highway Bridge based on ANSYS8.0 is built. Mixed-auto regressive model is applied to a wind field simulation for the whole bridge, and the time-domain expression of the self-excited forces is established. The lateral buffeting response of the bridge is analyzed by using step-by-step numerical integration techniques. Furthermore, this paper puts forward the measure of setting a viscous damper between the pylon and the beam which have an angle of 45° to the bridge lognitudinal axis to reduce the buffeting response, for which five different conditions are considered. The results display that： the lateral buffeting of the bridge deck is rather serious, so it is necessary to control the windinduced responses. By such kind of damper, the displacement and the acceleration of the bridge deck are both reduced greatly, but the internal force of the components of the structure has no increasing. The vibration reduction effects become more prominent by increasing the viseousity factor, but there is an optimum value.