格栅矩形水箱TLD振动特性及在结构减振中的应用

发布时间：2018-04-19 01:37

本文选题：桥梁结构 + 振动控制　；参考：《湖南大学》2015年硕士论文

【摘要】：随着轻质高强材料的大量应用及设计方法的进步,桥梁结构向大跨、轻柔及低阻尼方向发展,加剧了结构在风、地震及行人等动力荷载作用下响应。过大的结构振动影响舒适性,造成结构疲劳,严重时威胁结构安全。开发和应用阻尼器抑制结构的振动一直是桥梁抗风抗震等领域的前沿研究课题。调谐液体阻尼器(Tuned Liquid Dampers,简称TLD)由于具有造价低、易于安装、多方向控制、在小振幅下启动等优点,已在很多高层建筑上应用。刚性水箱中液体晃动具有很强的非线性特性,与激励幅值、激励频率等参数有关,造成TLD的力学模型相当复杂。本文主要研究纯水及格栅TLD的动力学特性及应用TLD进行人行桥的侧向减振问题。论文主要内容包括以下几个方面:(1)本文首先回顾了用于模拟纯水TLD的等效non-linear stiffness and damping(简称NSD)模型及模型参数(非线性刚度和非线性阻尼)的影响因素。基于等效NSD模型建立结构—TLD的运动方程,导出两自由度系统在简谐激励下主结构的位移动力放大因子,得到动力放大因子最大值最小化的TLD的参数优化,并进行了参数分析。最后以一倒立式框架为例,设计制作了TLD水箱,进行了控制结构一阶侧向振动响应的TLD—结构振动台试验,测定结构在不同激振频率作用下的稳态位移响应,并与数值优化的结果进行对比,验证了参数优化的有效性。(2)为解决纯水TLD中阻尼过低引起的液面晃动强非线性问题,研究了格栅TLD的振动特性。采用振动台试验及无接触视频位移测试系统测定了不同激振幅值、格栅个数、格栅放置位置、格栅阻塞比等参数下水箱侧壁无量纲波高随激振频率的变化,结果表明增设格栅后TLD的非线性特性显著降低,基本避免了纯水TLD中存在的“跳频”、“频率偏移”等非线性特征。基于波动理论推导了增加格栅的TLD的等效线性调谐质量阻尼器(tuned mass dampers简称TMD)模型,得到了模拟TLD的等效质量、等效刚度及依激励幅值而变化的等效阻尼比。最后对格栅TLD—主结构的响应进行参数优化得到格栅TLD的最优参数数值解。(3)建立某景区人行悬索桥有限元模型,分析得到结构的各阶振型、模态频率和模态质量等动力特性参数,并基于等效简谐力荷载及随机步行力荷载两种模型分析了人行桥的侧向动力响应。以控制该桥横向振动为目标,进行TLD的参数优化以及TLD在人行桥上的分布位置,最后通过分析得到人行桥在两类荷载模型作用下在安装TLD前后的侧向加速度响应,得出TLD控制人行桥振动的有效性。
[Abstract]:With the extensive application of lightweight and high-strength materials and the development of design methods, the bridge structure develops towards the direction of long span, soft and low damping, which intensifies the response of the structure to the dynamic loads such as wind, earthquake and pedestrian.Excessive structural vibration affects comfort and fatigue of structure, and threatens the safety of structure seriously.The development and application of dampers to suppress the vibration of structures has always been a frontier research topic in the field of bridge wind resistance and earthquake resistance.Tuned Liquid dampers (TLDs) have been applied in many high-rise buildings due to their advantages of low cost, easy installation, multi-direction control and small amplitude start-up.The liquid sloshing in the rigid tank has strong nonlinear characteristics, which is related to the excitation amplitude and the excitation frequency. The mechanical model of TLD is quite complex.In this paper, the dynamic characteristics of pure water and grid TLD and the lateral vibration reduction of footbridge with TLD are studied.The main contents of this paper are as follows: (1) this paper first reviews the equivalent non-linear stiffness and damping model used to simulate pure water TLD and the influence factors of model parameters (nonlinear stiffness and nonlinear damping).Based on the equivalent NSD model, the motion equation of the structure is established, and the displacement dynamic amplification factor of the main structure under harmonic excitation is derived, and the parameter optimization of the TLD with the minimization of the maximum dynamic amplification factor is obtained, and the parameter analysis is carried out.Finally, taking an inverted frame as an example, the TLD water tank is designed and manufactured, and the TLD-structure vibration table test is carried out to control the first order lateral vibration response of the structure. The steady-state displacement response of the structure under different excitation frequencies is measured.In order to solve the strongly nonlinear problem of liquid level sloshing caused by too low damping in pure water TLD, the vibration characteristics of grid TLD are studied.The vibration table test and contactless video displacement measurement system were used to measure the variation of the dimensionless wave height of the side wall of the water tank with the exciting frequency under the parameters of different exciting amplitude, the number of grid, the location of grid, the ratio of grid blocking and so on.The results show that the nonlinear characteristics of TLD are significantly reduced with the addition of grille, and the nonlinear characteristics such as "frequency hopping" and "frequency offset" in pure water TLD are basically avoided.Based on the wave theory, the equivalent linear tuned mass dampers (tuned mass dampers) model of TLD with additional grille is derived, and the equivalent mass, equivalent stiffness and equivalent damping ratio of simulated TLD are obtained.Finally, a finite element model of the pedestrian suspension bridge in a scenic spot is established by optimizing the parameters of the grille TLD- main structure and getting the numerical solution of the optimal parameters of the grid TLD.Dynamic parameters such as modal frequency and modal mass are used to analyze the lateral dynamic response of footbridge based on equivalent harmonic load and random walking force.In order to control the lateral vibration of the bridge, the parameter optimization of TLD and the distribution of TLD on the footbridge are carried out. Finally, the lateral acceleration response of the footbridge under the action of two kinds of load models before and after the installation of TLD is obtained.The effectiveness of TLD in controlling the vibration of footbridge is obtained.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441.3

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