【作者】 何文飞；

【导师】 陈政清； 华旭刚；

【作者基本信息】 湖南大学 ， 桥梁与隧道工程， 2009， 硕士

【摘要】 高耸格构式塔架一类结构是一种特殊的结构形式,其塔身镂空、高度高、外形细长,不仅在电力、通讯、广播电视等领域较为常见,在大跨度桥梁施工中也有广泛应用。高耸格构式塔架的外形特征决定了风荷载是其控制荷载,随着需求的提高和技术的进步,结构日益向着更高、更轻、更柔和低阻尼的方向发展,使得结构对风荷载的动力敏感性进一步增强。因此,对高耸格构式塔架进行风振响应研究显得尤为必要。本文以拟建设中的国家电网1000kV特高压输电网络中的一座典型自立式输电塔为例,从时域分析、频域分析及风洞试验三方面开展了高耸格构式塔架一类结构的风振响应及风振系数研究,主要内容包括:(1)建立了输电塔的空间有限元模型,通过分析确定模型的真实性。采用谐波合成法模拟了输电塔结构的脉动风速时程。在此基础上,将模拟得到的风荷载以结点力的方式加到有限元模型上,在时域内用Newmark法计算了输电塔的顺风向风振响应。频谱分析表明风振响应主要由第一阶模态响应控制。进一步分析了风振响应随风速、阻尼比等参数的变化关系。(2)根据相似原理设计制作了气弹模型,在风洞中模拟了大气边界层紊流。在紊流风场中对气弹模型进行了风洞试验,测得了模型加速度响应,将试验结果换算到原型,计算原型各测点的加速度响应均方差值,分析了加速度响应均方差随风速和风向角的变化规律。(3)按单模态随机振动理论方法,对高耸格构式塔架顺风向风振系数进行了频域理论分析,并与风洞试验结果、时域分析结果及建筑结构荷载规范结果进行了分析比较。由频域分析、时域分析及试验得到的风振系数基本一致。而由建筑规范得到的输电塔风振系数显著大于理论分析及风洞试验结果,高估输电塔的风振响应,不宜直接用于输电塔抗风设计。提出了用于风振系数计算的等效宽度的概念,比直接应用规范更加合理。(4)研究了紊流积分尺度对高耸格构式塔架顺风向风振系数的影响,结果表明紊流积分尺度对结构共振响分量应有显著影响,对结构的总响应影响也较大。这一影响随着结构阻尼、结构频率与风谱卓越频率的比值的增加而减弱。考虑到风洞试验技术无法满足紊流积分尺度的模拟,提出了一套较为通用的紊流积分尺度修正系数,可对风洞试验结果修正。更多还原

【Abstract】 High-rise lattice towers are a special kind of flexible structures because of being hollow-out and high flexibility. It has been widely applied in civil engineering infrastructures such as power transmission, communication, broadcasting television systems and construction phase of large-span bridges. Due to its characteristic of geometrical shape, the dominating load of high-rise lattice towers is wind load. With the growth of demand and progress of technique, it has been developed to be much higher, lighter and softer, intensifying its sensitivity to wind load. Therefore, it is of paramount significance to study the wind-induced dynamic response of high-rise lattice towers.By taking a typical transmission tower in State Grid’s 1000kV UHV transmission line as example, the wind-induced dynamic response of high-rise lattice towers is investigated in the present study, and the main contents are as follows:(1) The finite element model of the target tower is established, and the fidelity of this model is validated by analysis. The wind loads acting on transmission tower are digitally simulated by wave superposition method and applied to the finite elemnt model to obtain the structural response in time domain. It is shown that the first mode contributes predominatly the overall response. The variation of structural response of wind velocity and damping ratio is also investigated.(2) The aeroelastic model of the attendant tower is designed and manufactured following similarity criteria. The boundary layer wind is simulated in wind tunnel with passive method. The dynamic response in turbulence flow is measured for a wide range of wind velocity and wind attack (yaw) angle. The experimental results are converted to the real structure according to the required similarity criteria. The RMS of acceleration response are calculated, the rules by which the RMS responses varies with the wind velocity and wind directional angels are analyzed.(3) According to random vibration theory considering a single mode, along-wind gust loading factors for the lattice tower are determined in the frequency domain, the results are compared with those obtained from the time-domain method, wind tunnel testing as well as from the Wind Load Specification for building structures, China. A rough consistency in the results obtained from the time-domain and frequency-domain methods and wind tunnel testing is observed. However, the gust loading factors obtained with Wind Load Specificaiton is considerably larger than the above theoretical and experimental results, and is unsuitable for wind resistant design for transmission line towers. Thus, a parameter of equivalent width of the tower is suggested and is used to determine the gust loading factor, more reasonable results than the original specification is obtained.(4) The effect of turbulence length scale on dynamic response is investigated by using the formula derived from random vibration theory considering the first mode. It is shown that the turbulence length scale has a significant effect on the resonance response and has a noticeable effect on the overall response. Such an effect decreases with the increase of structural damping and the ratio of structural modal frequency to predominant frequency in the wind velocity spectrum. In recognizing that the present wind tunnel testing technique cannot simulate the turbulence length adequately, a set of correction coefficients are developed and may be used when the turbulence length scale is not appropriately scaled in wind tunnel testing.更多还原