流线型箱梁断面非线性自激力与非线性颤振响应研究

发布时间：2018-07-03 08:53

  本文选题：大跨度桥梁 + 流线型箱梁　； 参考：《西南交通大学》2015年博士论文

【摘要】：本论文首先回顾了大跨度桥梁抗风研究的发展历程,介绍了自激气动力的研究现状和获取途径。随后基于CFD数值模拟,研究薄平板和流线型箱梁断面的自激力特性,并通过流场显示,考查自激力非线性成分与典型流场特征之间的关系。引入特定的假设条件,通过理论推导,建立了桥梁二维非线性颤振响应分析的一般方法,并在此基础上讨论结构阻尼比模型的数学形式对桥梁非线性颤振幅值响应的影响。本文的主要研究内容有：(1)提出了多变形子区域的动网格方法,结合刚性网格技术和标准弹簧光顺法,实现桥梁断面大振幅变形运动时网格质量的良好控制。(2)研究大振幅条件下薄平板和流线型箱梁断面的自激力。运动振幅越大,高次谐波成分在整个气动力中所占的比例也越大。同等振幅条件下,对纯扭转运动而言,高折算风速下的自激力非线性效应更显著,但对纯竖弯运动而言,则是低折算风速下的自激力非线性更显著。(3)研究薄平板大振幅条件下的流场。流动分离不是气动自激力出现高频分量的原因,平板前缘流动分离影响自激气动力的基频幅值,而气动力高次谐波分量所占比例与流场中二次涡的强度成正相关。(4)研究流线型箱梁断面大振幅条件下的流场。断面单侧流场出现漩涡反向的现象与气动力出现高次谐波分量具备同时性。(5)在假设桥梁颤振是同一频率简谐竖向和简谐扭转运动耦合的基础之上,将颤振导数表述为折算频率和运动振幅的二维函数即非线性颤振导数,以振动系统的总阻尼再次为零作为振动振幅稳定的判据,建立了一种非线性颤振分析的基本方法。(6)研究南京四桥断面的非线性颤振幅值响应。即使其颤振临界风速被超过后,颤振响应也可能维持在一定的振幅水平上,对颤振响应振幅起决定作用的是颤振导数A2*构成的气动正阻尼和与A1*、H3*有关的耦合气动负阻尼。(7)研究结构阻尼比模型的数学形式对非线性颤振响应的影响。当结构阻尼比为常数型时,结构阻尼无法抑制颤振发散。当结构阻尼比为线性比例型时,阻尼比随振幅变化的斜率构成了抑制颤振响应的重要因素。当结构阻尼比为渐近型时,其振幅响应曲线的形状介于常数型阻尼比和线性比例阻尼比的振幅响应曲线之间。
[Abstract]:In this paper, the development of wind resistance research of long span bridges is reviewed, and the research status and ways of obtaining self-excited gas dynamics are introduced. Then, based on CFD numerical simulation, the self-excited force characteristics of thin plate and streamlined box girder section are studied, and the relationship between the nonlinear components of self-excited force and the characteristics of typical flow field is investigated through the flow field. A general method for analyzing the nonlinear flutter response of a bridge is established by introducing specific assumptions and theoretical derivation. On the basis of this, the influence of the mathematical form of the damping ratio model on the amplitude response of the nonlinear vibration of the bridge is discussed. The main contents of this paper are as follows: (1) A dynamic mesh method for multi-deformed subregions is proposed, which combines rigid mesh technique and standard spring fairing method. The mesh quality can be controlled well under the condition of large amplitude deformation of bridge section. (2) the self-excited force of thin slab and streamlined box girder section is studied under the condition of large amplitude. The larger the amplitude of motion, the larger the proportion of higher harmonic components in the whole aerodynamic force. For pure torsional motion with the same amplitude, the nonlinear effect of self-excited force at high converted wind speed is more significant, but for pure vertical bending motion, It is more obvious that the self-excited force is nonlinear at low converted wind speed. (3) the flow field under the condition of large amplitude of thin plate is studied. Flow separation is not the cause of the high frequency component of aerodynamic self-excited force. The flow separation at the leading edge of the plate affects the fundamental frequency amplitude of the self-excited force. However, the proportion of aerodynamic high-order harmonic components is positively correlated with the intensity of secondary vortices in the flow field. (4) the flow field under the condition of large amplitude of streamlined box girder section is studied. The phenomenon of vortex reverse in the flow field on one side of the cross-section is simultaneous with the high harmonic component of aerodynamic force. (5) based on the assumption that the bridge flutter is coupled with the harmonic vertical and torsional motions of the same frequency, The flutter derivative is expressed as a two-dimensional function of the converted frequency and motion amplitude, that is, the nonlinear flutter derivative. The total damping of the vibration system is again zero as the criterion of vibration amplitude stability. A basic method of nonlinear flutter analysis is established. (6) the nonlinear vibration amplitude response of Nanjing fourth Bridge section is studied. Even if the critical flutter velocity is exceeded, the flutter response may be maintained at a certain amplitude level. The flutter response amplitude is determined by the aerodynamic positive damping formed by the flutter derivative A2 * and the coupled negative aerodynamic damping associated with A1H3 *. (7) the influence of the mathematical form of the structural damping ratio model on the nonlinear flutter response is studied. When the damping ratio of the structure is constant, the structure damping can not restrain the flutter divergence. When the damping ratio of the structure is linear proportional, the slope of the damping ratio with the amplitude is an important factor to suppress the flutter response. When the damping ratio of the structure is asymptotic, the shape of the amplitude response curve is between the constant damping ratio and the linear proportional damping ratio.
【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U441.3
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本文编号：2093085