抗风缆对大跨度悬索桥风致静力失稳及抖振的控制研究

发布时间：2018-03-05 08:42

本文选题：大跨度悬索桥　切入点：动力特性　出处：《内蒙古科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着缆索结构桥梁的跨度不断增大，其刚度和阻尼不断下降，对风荷载更加敏感。在很多情况下，，此类型桥梁的抗风问题成为桥梁设计时要考虑的首要问题。本文以矮寨大桥为工程背景，研究施加抗风缆对桥梁静力失稳临界风速、跨中节点位移随风速的变化过程和在自然风作用下抖振响应有何变化，为相似桥梁的抗风设计提供参考。首先，本文建立了矮寨大桥原桥有限元模型和施加抗风缆后的有限元模型，通过改变抗风缆拉杆与桥面的角度、拉杆长度、抗风缆和拉杆的横截面积、抗风缆和拉杆的初应变，研究这四种抗风缆参数对桥梁动力特性的影响规律，主要通过比较桥梁关键频率来确定抗风缆的最优参数。计算结果表明：抗风缆的施加使桥梁的各阶频率增大，表明刚度增大。抗风缆拉杆与桥面的角度为90度的效果最好，拉杆长度对桥梁的动力特性影响不明显，抗风缆和拉杆的横截面积越大,桥梁的频率增大越显著，抗风缆和拉杆的初应变增大，桥梁频率显著增大。其次，本文用线性方法计算了施加抗风缆前后桥梁的失稳临界风速，用三维非线性方法计算了施加抗风缆前后桥梁跨中节点的位移和主缆跨中的轴力随风速的变化，得出桥梁在施加抗风缆后横向倾侧失稳风速和静力扭转失稳风速分别提高10.1%和8.9%，跨中位移显著减小。通过主缆跨中轴力变化发现：施加抗风缆前桥梁失稳风速在120m/s左右,而施加抗风缆后桥梁的主缆跨中轴力变化很稳定，直到风速180m/s时轴力还没出现突变的分布，表明施加抗风缆后结构刚度和稳定性都有所增强。最后，根据随机振动理论，基于线性滤波法用MATLAB软件模拟了桥梁跨中节点处的水平脉动风和竖向脉动风时程曲线，并根据达文波特力学模型把随机风转化为随机抖振力。计算结构时程响应表明：施加抗风缆后桥梁的振幅减小，抗风效果明显。通过计算静力失稳临界风速、跨中节点随风速变化和随机抖振响应表明：施加抗风缆后静力失稳临界风速有所提高，抗风缆对桥梁的竖向平均振幅有稍稍增大，对桥梁横向和扭转角的振幅有很强的抑制作用，而且横向和扭转角的振幅更加平稳，表明抗风缆起到了良好的抗风效果。
[Abstract]:As the span of cable-structure bridges increases, their stiffness and damping decrease, and they are more sensitive to wind load. In many cases, The wind-resistant problem of this type of bridge becomes the most important problem to be considered in the design of the bridge. In this paper, the critical wind speed of static instability caused by wind resistant cables on the bridge is studied, taking the Aizhai Bridge as the engineering background. The variation of node displacement with wind speed and buffeting response under natural wind will provide reference for wind-resistant design of similar bridges. First of all, the finite element model of the original bridge and the wind resistant cable is established in this paper. By changing the angle between the wind resistant cable and the bridge deck, the length of the pull rod, the cross-sectional area of the wind resistant cable and the tie rod, The influence of the four kinds of wind-resistant cable parameters on the dynamic characteristics of the bridge is studied by the initial strain of the wind-resistant cable and the pull rod. The optimum parameters of wind-resistant cable are determined by comparing the key frequencies of the bridge. The calculation results show that the application of the wind-resistant cable increases the frequency of each order of the bridge, indicating that the stiffness is increased, and the angle between the wind-resistant cable rod and the bridge deck is 90 degrees. The more the cross-sectional area of wind cables and strands is, the more significant the frequency of bridges is, and the initial strain of wind cables and strands increases, and the frequency of bridges increases significantly. Secondly, the linear method is used to calculate the instability critical wind speed of the bridge before and after the application of the wind resistant cable, and the displacement of the mid-span node of the bridge and the axial force of the main cable span with the wind speed are calculated by the three-dimensional nonlinear method before and after the application of the anti-wind cable. The results show that the lateral wind speed and static torsional wind speed of the bridge are increased by 10.1% and 8.9 respectively after the application of the wind resistant cable, and the mid-span displacement is significantly reduced. It is found that the unsteady wind speed of the bridge is about 120m / s before the application of the wind resistant cable through the variation of the mid-span axial force of the main cable. The axial force of the main cable is stable until the wind speed is 180m / s, which indicates that the stiffness and stability of the structure are enhanced after the application of the wind-resistant cable. Finally, according to the random vibration theory, the horizontal and vertical pulsating wind history curves at the middle node of the bridge are simulated with MATLAB software based on the linear filtering method. According to the Davenport mechanics model, the random wind is transformed into the random buffeting force, and the time-history response of the structure shows that the amplitude of the bridge decreases with the application of the wind-resistant cable, and the wind-resistant effect is obvious. By calculating the critical wind speed of static instability, the variation of span node with the wind speed and the random buffeting response show that the critical wind speed of static instability increases after applying the wind resistant cable, and the vertical mean amplitude of the bridge is slightly increased by the wind resistant cable. The amplitude of the transverse and torsional angle of the bridge is strongly inhibited, and the amplitude of the transverse and torsional angle is more stable, which indicates that the wind-resistant cable has a good wind-resistant effect.
【学位授予单位】：内蒙古科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441.3

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