【作者】 肖正直；

【导师】 李正良；

【作者基本信息】 重庆大学 ， 工程力学， 2009， 博士

【摘要】 输电塔线体系的抗灾害性研究尚处于初期,无论是灾害荷载作用机理,还是结构分析方法、设计理论、振动控制等方面均存在很多缺陷,致使输电塔的倒塔破坏时有发生,经济损失巨大,严重影响国民经济建设和生活秩序。风荷载又是其主要的动力荷载,动力风效应分析的正确性和精度将直接影响到结构的安全与合理。因此有必要对输电塔线体系的风荷载作用模型、风振响应、等效风荷载及风洞实验进行深入研究。本文围绕输电塔的风振响应和等效风荷载,主要开展了以下几个方面的工作:(1)初步解决了格构式输电塔气弹模型设计的难题。由于格构式输电塔结构质量轻、刚度大,采用传统的气动弹性模型设计方法无法实现输电塔结构的气弹模型设计,刚性节段加“V”型弹簧片法能很好地模拟输电塔结构的动力特性。(2)气动阻尼是输电塔结构风振响应分析的重要参数,通过HHT方法结合RDT法实现了输电塔线体系环境激励下的气动阻尼的识别,为输电塔线体系的风振响应分析提供了基础。(3)根据高频天平技术原理及基于准定常假设条件下,推导了输电塔风荷载空间分布的计算公式,为输电塔的风致振动研究提供了一条重要途径,也是对高频天平测力实验局限性的一种可靠方便的扩展。(4)通过自振特性分析确定了弯剪型层模型作为输电塔动力计算的简化模型;根据准定常假设认为来流在结构表面重分布可以忽略,结构上一点所受的顺风向脉动风荷载只与该点来流的风速有关,确定了输电塔顺风向风荷载作用模型。作用在结构上的横风向风荷载和扭转风荷载主要由紊流风、分离剪切流与结构侧面相互作用、尾流激励以及漩涡随机脱落等共同作用的结果,结构自身的形状对其影响较大,因此横风向风荷载及扭转风荷载不在适用于用横风向风速谱直接转化得到,根据高频天平测力实验得到的基底弯矩,通过分段估计法得到了横风向风荷载的分布。发展了用于输电塔耦合抖振分析的有限元CQC法、SRSS法和虚拟激励法。(5)谐波合成法是一种精度较高且无条件稳定的随机过程模拟方法,本文在单维多变量随机风场合成方法的基础上,引入了纵向与竖向脉动风速的交叉谱的影响;经过对模拟样本的谱密度函数、相关函数检验验证,该方法能准确有效地模拟出符合要求的多维多变量随机样本;在此基础上实现了输电塔线体系时域抖振分析。(6)发展了基于荷载响应相关法的输电塔顺风向的等效风荷载研究。考虑输电塔结构截面收缩的影响,推导了简单输电塔结构顺风向、横风向及扭转方向的一阶广义荷载谱的振型修正系数。基于分段估计法推导的三维风荷载互谱,研究了输电塔结构三个正交方向的等效风荷载。更多还原

【Abstract】 The study on the disaster tolerance of transmission tower-line system is still in the initial stage, hence a lot of defects in many aspects, such as mechanism of disaster load, structure analysis method, design theory and vibration control; consequently, the collapse and damage of transmission tower happen occasionally, resulting in huge economic losses and thus serious impacts on national economic construction and life orders. Wind load is the primary dynamic load of transmission tower-line system, so the correctness and accuracy of analysis on dynamic wind effect will directly affect the safety and rationality of structure. Therefore, it is necessary to further research transmission tower-line system in aspects of wind load action model, wind-induced response, equivalent wind load as well as wind tunnel experiment. Focusing on wind-induced response and equivalent wind load of transmission tower, this article mainly reaches achievements as following:(1) This article initially solves the problem about aeroelastic model design of lattice transmission tower. Owing to the light structure and big stiffness of lattice transmission tower, it is impossible to realize aeroelastic mode design for lattice transmission tower in traditional aeroelastic model design method, but the method of rigid section plus V-shape spring strip can simulate the dynamic characteristics of transmission power structure.(2) Aerodynamic damping is an important parameter for wind-induced response analysis on transmission tower structure. Through the combination of HHT method and RDT method, this article realizes aerodynamic damping identification of transmission tower-line system under ambient excitation, providing a basis for the wind-induced response analysis of transmission tower-line system.(3) According to the technical principles of high frequency balance and based on the quasi-steady assumption condition, this article derives a computing formula of space distribution of wind load on transmission tower, providing an important channel for the study on wind-induced vibration of transmission tower as well as a kind of convenient and reliable development of force measurement range of high frequency balance.(4) Through analysis on natural vibration characteristics, this article determines the simplified model of shear-bending storey model as used for dynamical computation; according to quasi-steady assumption, it is considered that the redistribution of incoming flow in structure surface can be ignored, the along-wind fluctuating wind load on one point of the structure is merely related to the wind speed at this very point, and thus the along-wind load action model of transmission tower is defined. Across-wind load and torsional wind load acting on the structure mainly result from the interaction of turbulent wind and separated shear flow with structure aspect and the combined action of wake excitation and random vortex shedding, and furthermore are significantly affected by the structural shape itself; therefore, across-wind load and torsional wind load are no longer applicable to the across-wind load distribution that is transformed directly from across-wind speed spectrum and derived through section estimation method according to the base bending moment from HFFB experiment. This article also develops finite-element CQC method, SRSS method and pseudo excitation method that can be used for transmission tower coupled buffeting analysis.(5) Harmonic synthesis is a simulation method of stochastic process, which is of high precision and unconditional stability. Based on the synthetic method of single-dimensional multivariable stochastic wind field, this article introduces the impact of cross spectrum of vertical and longitudinal turbulent wind velocity; after examination of spectrum density function and other related functions of simulation samples, it is verified that with this method, multi-dimensional multivariate stochastic samples meeting relevant requirements can be simulated accurately and effectively; on above basis, time domain buffering analysis of transmission tower-line system is realized.(6) This article develops the study on along-wind equivalent wind load of transmission tower based on LRC method. Considering the affect of cross-section contraction of transmission tower structure, this article derives a correction coefficient of mode shape for the generalized force spectrum of the first mode of simple transmission tower in along-wind, across-wind and torsional directions. In the three dimensional wind load cross-spectrum derived based on section estimation method, this article studies the equivalent wind load in three orthogonal directions of transmission tower structure.更多还原