椭圆形高耸结构风荷载及风致响应研究

发布时间：2018-04-19 23:07

本文选题：风洞试验 + 高耸结构　；参考：《湖南大学》2015年硕士论文

【摘要】：航空塔、电视塔等高耸结构构造型细长、柔度大,对随机的风荷载作用较为敏感,因此容易引起结构的疲劳和破坏,而椭圆形高耸结构以其特殊的流线型截面形式受到了人们的关注。本文首先通过对武汉天河国际机场一椭圆形航空塔的风压和风荷载特性分析,得到了一些有用的结论。为了获得更多普遍性的结论,又设计了6种不同高宽比和厚宽比的标准椭圆形高耸结构刚性模型,根据刚性模型同步测压风洞实验方法得到的实验数据,讨论了标准椭圆形高耸结构的风压分布、风压谱及相干性以及各层的三分力系数、风荷载功率谱等。研究的具体内容如下:结合武汉天河国际机场三期扩建空管工程塔台刚性模型同步测压风洞试验结果,对椭圆形高耸结构的风荷载特性进行了研究。讨论了典型风向角下不同测点层的平均风压系数和极值风压系数的分布规律;基于测点层的风荷载合力时程,采用快速傅里叶变换的方法,得到了椭圆形高耸结构在90°风向角(最大迎风面)下的三维层风荷载功率谱,并采用经验公式对其进行拟合,拟合效果较好;采用LRC法计算了平均风荷载、背景和共振等效静力风荷载,并将结果与荷载规范建议的惯性风荷载法计算结果对比,发现两种方法得到的等效静力风荷载吻合较好。对6种不同高宽比和厚宽比的椭圆形高耸结构模型进行了刚性模型同步测压风洞试验,选取了模型3(H/(?)=7.5,D/B=0.75)的风洞试验结果,研究了风向角、测点位置及测点高度对模型表面的风压系数、风压系数功率谱及相干性的影响,得到了模型在长轴迎风时的漩涡脱落频率,并定义了模型在长轴迎风时的迎风面、过渡区和背风面的分界点。利用经验公式拟合了典型测点的相干函数,计算结果表明椭圆形高耸结构在过渡区水平相干性最大,在曲率较大处竖向相干性最大,但水平和竖向相干性都比矩形结构低。探讨了风场类别、厚宽比和高宽比对椭圆形高耸结构层三分力系数和三维风荷载功率谱的影响。采用不同的荷载谱数学模型对三维风荷载功率谱进行拟合,并以湍流度和厚宽比为基本变量,对荷载谱数学模型中的参数进行二次拟合,建立了椭圆形高耸结构无量纲层三维风荷载功率谱关于湍流度和厚宽比的闭合公式,经验证拟合效果较好。并根据这些公式计算出了武汉航空塔各楼层的顺风向位移响应均方根。为了进一步了解椭圆形高耸结构顺风向和横风向风荷载与扭转向风荷载的关系,给出了模型3在不同厚宽比下的顺-扭和横-扭相干函数曲线。结果表明椭圆形高耸结构横-扭相干性一般大于顺-扭相干性,且较高的横-扭相干性维持在较宽的频率范围内或者具有多个峰值,而顺-扭相干性一般较小,但在厚宽比接近1时相干性较大,验证了厚宽比接近1时层扭矩系数最大的结论。
[Abstract]:The tall structures such as aerial towers and television towers are slender, flexible and sensitive to random wind loads, so they can easily cause fatigue and destruction of structures. The elliptical towering structure has attracted people's attention because of its special streamline section form. In this paper, the characteristics of wind pressure and wind load of an elliptical air tower in Wuhan Tianhe International Airport are analyzed, and some useful conclusions are obtained. In order to get more general conclusion, six standard elliptical tall structure rigid models with different aspect ratio and thick-width ratio are designed. According to the experimental data obtained from the wind tunnel experiment method of simultaneous pressure measurement of rigid model, The wind pressure distribution, wind pressure spectrum and coherence, the three-point force coefficient of each layer and the wind load power spectrum of the standard elliptical towering structure are discussed. The main contents are as follows: combined with the wind tunnel test results of tower rigid model of Wuhan Tianhe International Airport, the wind load characteristics of elliptical towering structures are studied. The distribution law of the average wind pressure coefficient and extreme wind pressure coefficient of different measuring points under typical wind direction angle are discussed, and the fast Fourier transform method is used based on the wind load resultant force time history of the measured point layer. The three-dimension wind load power spectrum of elliptical towering structure under 90 掳wind direction angle (maximum upwind surface) is obtained, and the empirical formula is used to fit it. The fitting effect is good. The average wind load is calculated by LRC method. The background and resonance equivalent static wind loads are compared with the results calculated by the inertial wind load method proposed in the load code. It is found that the equivalent static wind loads obtained by the two methods are in good agreement with each other. Six kinds of elliptical towering structure models with different aspect ratio and thickness ratio were tested in wind tunnel with rigid model synchronously. The wind tunnel test results of model 3 / H / D / B 0.75) were selected, and the wind direction angle was studied. The influence of measuring point position and height on the wind pressure coefficient, power spectrum and coherence of the model surface is obtained. The vortex shedding frequency of the model under the long axis upwind is obtained, and the upwind surface of the model during the long axis upwind is defined. The boundary point between the transition zone and the leeward surface. The coherence function of typical measured points is fitted by empirical formula. The calculation results show that the horizontal coherence of elliptical tall structures is the largest in the transition zone and the vertical coherence is the largest in the larger curvature, but the horizontal and vertical coherence is lower than that of the rectangular structures. The effects of wind field types, ratio of thickness to width and ratio of height to width on the three-point force coefficient and the three-dimensional wind load power spectrum of elliptical towering structures are discussed. Three dimensional wind load power spectrum is fitted with different load spectrum mathematical models, and the parameters of load spectrum mathematical model are fitted twice, taking turbulence degree and thickness width ratio as basic variables. The closure formula of three-dimensional wind load power spectrum of elliptical towering structures for turbulence and thickness to width ratio is established. The results show that the fitting effect is good. According to these formulas, the root mean square of the downwind displacement response of each floor of Wuhan aeronautical tower is calculated. In order to further understand the relationship between wind load and torsional wind load of elliptical towering structures, the coherence function curves of para-torsion and transverse torsion under different thick-width ratios are given in model 3. The results show that the transverse and torsional coherence of elliptical towering structures is generally greater than that of para-torsional coherence, and the higher transverse and torsional coherence is maintained in a wide frequency range or has multiple peaks, while the cis-torsional coherence is generally smaller. However, when the ratio of thickness to width is close to 1, the coherence is larger, which verifies the conclusion that the ratio of thickness to width is close to 1, and the maximum torque coefficient 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】：TU312.1

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