【作者】 韩艳；

【导师】 陈政清；

【作者基本信息】 湖南大学 ， 桥梁与隧道工程， 2008， 博士

【摘要】 论文首先回顾了气动导纳研究现状以及目前存在的问题,明确了气动导纳是桥梁抖振分析中至关重要的气动参数,它的研究是今后桥梁抖振精细化分析中一个重要的研究方向。本文利用风洞试验、数值模拟和理论分析相结合的方法,对薄平板和三种典型桥梁断面的气动导纳进行了详细和深入的研究。利用实测的气动导纳函数对桥梁结构抖振响应进行了精细化分析,分别提出了考虑气动导纳修正和抖振力空间相关性影响的频域分析方法和时域分析方法。本文还对结构进行了全桥气弹模型风洞试验研究,验证本文提出的抖振分析理论的正确性。最后总结起来本文主要进行了以下几个方面的工作:(1)论文通过对气动导纳研究(包括气动导纳的来源、理论研究、试验研究、测量技术、经验公式)结果的回顾和总结,发现目前气动导纳研究的不足,明确论文研究内容;(2)对薄机翼基本理论进行了较深入研究,更深刻地理解了气动导纳的物理意义,为以后其它桥梁断面气动导纳的研究以及复气动导纳的提出奠定了理论基础。推导了薄机翼断面的静力三分力系数,给出了风攻角下理想平板的静力三分力系数,为接下来的薄平板模型静力三分力系数的试验、数值模拟研究提供理论参考;(3)提出了一种主动格栅技术,可以在风洞中同时产生单一频率的顺风向和竖风向的两个脉动分量。基于该技术推导提出了分离频率识别法下6个复气动导纳的定义式,并通过模拟数值信号检验了它的数值正确性;(4)根据提出的主动格栅技术开发了一套主动格栅装置,该装置可以产生顺风向和竖风向单一频率的谐波脉动风场,其紊流积分尺度可以达到几十米,克服了一直以来无法提高紊流积分尺度的困扰。开发了一套双天平水平测力装置,可以直接测定水平放置模型的抖振力。利用开发的主动格栅装置和双天平水平测力装置,实现6个复气动导纳的同时识别。对薄平板和三种典型桥梁断面的气动导纳进行了测量,并对测量结果进行了分析和讨论,得出重要的结论和结果;(5)基于分离频率识别方法,实现了气动导纳的CFD数值模拟研究。利用CFD数值模拟技术,对薄平板气动导纳进行研究,并与试验结果进行比较分析,得出一些有意义的结论;(6)提出了一种考虑抖振力空间相关性和气动导纳修正的适合于双肢薄壁高墩悬臂结构的抖振频域响应分析方法。以小关桥为例,给出了该桥施工阶段墩底内力的计算公式,分析了各脉动风荷载以及各部位上脉动风荷载对结构抖振响应的贡献,并且分析了抖振力空间相关性和气动导纳函数对结构抖振响应的影响;(7)提出了一种新的模拟随机风场的小波方法,该方法可以模拟脉动风的间歇性和局部相似性。目前只实现了一维单变量风场的模拟,有待进一步的拓展;(8)提出了一种基于抖振力空间相关性考虑气动导纳影响的抖振时域分析方法。运用该方法对双肢薄壁高墩悬臂结构进行了抖振分析,并将分析结果与频域分析结果进行比较,相互验证了两种方法的正确性;(9)开展了双肢薄壁高墩悬臂结构全桥气弹模型风洞试验研究,通过试验和频域、时域计算的结果比较,验证两种抖振分析理论的正确性;(10)利用第七章提出的抖振时域方法对东海大桥进行了抖振响应分析,将计算分析结果与相关参考文献结果进行比较,比较结果显示本文时域方法的计算结果与参考文献结果基本一致,验证了本文时域方法的正确性和适用性。更多还原

【Abstract】 The research status of aerodynamic admittance functions (AAFs) was first reviewed and problems in the research were issued in the thesis. Aerodynamic admittance functions (AAFs) are one of the important aerodynamic parameters affecting buffeting response of long-span bridges. The development of rational AAFs is an important research field towards the refined/improved buffeting theory. This thesis is concerned with modeling and identification of AAFs from wind tunnel testing data for thin plate section and several types of bridge cross sections, the proposal of refined buffeting theory formulated taking into account both the developed AAFs and measured coherence/correlation of buffeting forces in frequency domain and in time domain, and the experimental validation of refined buffeting theory with the use of testing results from the full-scale aeroelastic model of a bridge in wind tunnel. Wind tunnel testing, numerical simulation and theoretical formulation are used in this study. In Sum, the main contents are concluded as follows.(1) After a careful and detailed review of the current research status concerning aerodynamic admittance functions, including the origin, theoretical and experimental study, testing setup and empirical formula of AAFs, issues are pinpointed and the content and objectives of the present research are confirmed.(2) The forces acting on thin airfoil are re-examined in depth to provide the physical meanings and formulations of aerodynamic admittance functions and to lay down the theory foundation for developing the AAFs of other bridge sections. The aerostatic coefficients of thin airfoil are described. The theoretical aerostatic coefficients of ideal thin plate cross section at different wind attack angle are then derived. The derived coefficients provide the basis for wind tunnel testing and numerical simulation studies of thin plate section addressed in the third and fourth chapters.(3) An active turbulence generator technique is developed to generate the longitudinal and vertical components with a harmonic frequency at one time. A frequency-by-frequency method of identifying complex AAFs (CAAFs) is developed and formulas of CAAFs are derived. The method is validated the simulated‘experimental’data.(4) The active turbulence generator is devised following above philosophy and generating the oscillating longitudinal and vertical velocity components with a single frequency. The generator has the merit to provide deca-meters order of the turbulent integral scale of the generated harmonic oscillating wind field, which overcomes the difficulty to generate wind field with large turbulent integral scales. A horizontal setup of measuring force with double force balances is developed and used to measure the aerodynamic force acting on sectional models suspended in wind tunnel. Making use of experimental data, six CAAFs are successfully identified. CAAFs of the thin plate section and three kinds of other bridge section models are obtained. Many significant results and suggestions are obtained by comparing the experimental results.(5) Based on the frequency-by-frequency identifying method, the investigations of CAAFs using computational fluid dynamics (CFD) technique are carried out in the Chapter 5. CAAFs are investigated using the numerical simulation technique of CFD. The numerical results are compared with the experimental results and many significant results are obtained.(6) A frequency-domain method taking into account the modification of AAFs and coherence functions of buffeting forces is presented for analyzing the buffeting response of cantilever structures with twin-legged high piers. Taking Xiaoguan bridge as an example, the displacement responses and the internal forces at the bottom of the left pier of the bridge are obtained. The contributions of each component of the aerodynamic forces and of each part of the structure to buffeting response of the bridge are investigated. In addition, effects of AAFs and coherence of buffeting forces are studied on the buffeting response of the bridge.(7) A new wavelet method of simulating wind field is presented. The method can simulate the self-similarity and intermittency of turbulence. Up to now, the method can only simulate one-dimension and single-variant wind field and is worth of further research.(8) A time-domain method is formulated also considering the modification of CAAFs and coherence functions of buffeting forces. The buffeting response of cantilever structures with twin-legged high piers is now performed using time-domain method. It validates the consistency of the frequency- and time-domain methods by comparing results obtained from the two methods.(9) Aeroelastic model experiments of cantilever structures with twin-legged high piers are carried out in wind tunnel. The experimental results are compared with analytical results and validate the correctness of time-domain and frequency-domain methods presented in this thesis. (10) The time-domain method for buffeting analysis of bridges presented in Chapter 7 is extended to analyze buffeting response of Donghai Bridge. The results obtained from the present method of Chapter 7 are compared with the results obtained the results reported in the literature. The closeness of the two sets of results is observed.更多还原