悬浮隧道管体-锚索耦合系统的自由振动研究

Study on Free Vibration of Coupled System of Submerged Floating Tunnel Tube and Cable Anchor System

通过建立悬浮隧道计算模型,采用Morison公式计算管体和锚索在水中振动时所受的水体阻力,推导出悬浮隧道管体-锚索耦合系统的自由振动方程组,并在数值算例中求解频率、阻尼比等模态参数;同时进行参数研究,探究了影响模态参数的相关因素。结果表明,悬浮隧道管体-锚索耦合系统自由振动方程组能够揭示悬浮隧道管体和锚索之间的耦合作用的实质,方程中的锚索动张力项既作为管体受力之一来影响管体的模态,又受到管体振动的影响进而改变了锚索的模态;水体对结构模态参数的影响主要表现在Morison公式中的惯性力项,也即附连水质量上。受到附连水质量的影响,管体一到三阶自振频率和阻尼比及锚索的自振频率和阻尼比相较于在空气中均有一定程度的减小。同时隧道各项设计参数的改变也会使得管体和锚索的模态参数发生改变。

By establishing the calculation model of submerged floating tunnel and using the Morison formula to calculate the water resistances of the tunnel tube and the anchor cable,the free vibration equations of coupled system of submerged floating tunnel tube and cable anchor system are derived.Modal parameters such as frequency and damping ratio are solved in the numerical example.Also,the parameter study is carried out to explore the factors which influence the modal parameters.The results show that the free vibration equations of coupled system can reveal the essence of the coupling between the tunnel tube and the anchor cable.The dynamic tension term of the anchor cable not only affects the mode of the tube body as a force of the tube,but also is affected by the vibration of the tube and then changes the mode of the anchor cable.The influence of water on structural modal parameters is mainly caused by the inertial force term of Morison formula,namely the added water mass.Under the influence of the added water mass,the natural vibration frequency and damping ratio of the first to third order of the tube as well as the natural vibration frequency and damping ratio of the anchor cable are reduced to a certain extent compared with that in the air.Moreover,the variation of design parameters of tunnel will change the modal parameters of the tube and anchor cable.