【作者】 王锦文；

【导师】 瞿伟廉；

【作者基本信息】 武汉理工大学 ， 结构工程， 2008， 博士

【摘要】 高耸输电塔结构作为大型生命线工程的重要组成部分,风力是其主要的设计荷载。近年来输电线塔在强风作用下的倒塔破坏事件层出不穷,这不仅严重地影响着人们的生产建设,而且还会导致其它严重的次生灾害。因此,研究输电线塔结构在强风荷载作用下的倒塔破坏机理,确保风力作用下输电线路的正常工作,以及实时把握输电线塔结构的工作状态具有重要的工程意义。本文以汉江大跨越输电塔结构为研究背景,系统地研究了作用在输电线塔上的下击暴流强风荷载模型、输电线塔的非线性风振响应分析方法、输电塔杆件的塑性疲劳破坏模型、输电塔结构在强风荷载作用下的倒塔破坏过程以及长期风荷载作用下输电塔杆件的裂纹萌生疲劳寿命。本文研究了输电塔线耦联体系有限元模型的建立方法,并提出用带初应力空间四节点索单元来模拟输电线。分析了塔线耦合体系的动力特性,研究了输电线对输电塔结构动力特性的影响。编写了输电塔线体系有限元模型的建立、静力分析、动力分析的一系列程序,解决了应用一些有限元软件计算繁琐、收敛速度慢、不能考虑自定义索单元等缺陷,成功实现了快速、准确地计算输电塔线耦合体系的静动力响应。并比较了输电线对输电塔结构风振响应的影响。由于下击暴流强风荷载的作用是输电塔结构倒塔破坏的重要原因,在广泛研究下击暴流特征的基础上,本文提出了用确定性时变过程描述下击暴流平均风速、用调制非平稳随机过程描述下击暴流脉动风速的下击暴流力学模型,并提出了数值模拟下击暴流强风荷载时程的方法,为输电塔结构的分析和设计提供强风荷载模型。通过对一批钢结构试件进行塑性范围内的等位移幅循环加载,测得不同位移幅值作用下试件的滞回曲线,统计了不同位移幅值循环加载时的极限循环次数和极限耗能,并研究了低周疲劳循环过程中杆件刚度变化的规律。鉴于目前广泛应用的破坏准则的一些缺陷,在钢杆件低周疲劳试验的基础上,提出了输电塔结构杆件基于塑性疲劳(s-n)曲线的破坏模型,改进了目前应用的一些破坏准则的缺陷。本文研究了输电线塔结构在下击暴流强风荷载作用下的弹塑性动力分析方法,并结合本文提出的基于塑性疲劳(s-n)曲线的破坏模型,仿真了输电线塔结构在下击暴流强风作用下的倒塔破坏过程,为输电塔结构破坏机理和破坏过程的研究奠定了基础。本文建立了风力作用下输电塔结构安全预警中裂纹萌生疲劳寿命评估方法。通过“安全预警系统实时识别作用在输电塔结构上的实时风荷载…-实时求取风荷载作用下结构构件的应力响应时程——基于Miner疲劳累积损伤准则利用雨流计数法计算各构件的实际风致疲劳累积损伤”和“不在线确定结构所在地按其强度归类的风荷载等级——统计不同等级风荷载在每年内出现的概率特性及其样本——估算结构各构件在剩余时间中的疲劳累积损伤”的方法来估算结构杆件的裂纹萌生疲劳寿命。更多还原

【Abstract】 Wind load is a very important designing load of high-rise transmission tower, which is the important component of large scale lifeline system. The collapse accidents of transmission towers occur now and then by wind excited, and high-rise transmission towers’ safety is directly influenced national productivity and people’s life. For a severe wind would be prone to bring out easy to result in elasto-plasticity behavior of the element, then induce the accumulated low-cycle fatigue damage and the collapse of the tower, studying on the structure’s failure or collapse mechanism, realizing the structure’s working status and insuring the security of service transmission symtem are very significant questions for discussion. Taking the Hanjiang long span transmission tower as the engineering background, the simulation method of downburst wind loads, analysis method of nonlinear transmission system’s wind-induced response, spatial steel element’s low-cycle fatigue failure model, the failure process of transmission tower under the severe wind load and long-standing wind induced crack initiation fatigue life evaluation technology are studied in this paper.In this thesis, the finite element model establishment method of transmission line’s cable-structure mixed system is studied. In order to simulate transmission line, a prestressed four-node isoparametric curved element is proposed and a series of its finite element formulas are derivated. Then cable-structure mixed system’s dynamic characteristics are analyzed and cable’s influence on the dynamic characteristics of the tower is studied. Cable-structure mixed system’s nonlinear static and dynamic analysis method are studied, and calculating code is compile for the establishing the model of the system, static and dynamic analysis using Matlab. The method and its code conquered many problems such as complicated calculating, difficult to converge and unable to consider the user-defined cable element and make the calculating on the efficient and accurate way. Then, the influence of the cable on the wind-induced response of the structure is discussed.Based on multidimensional stochastic vibration theory, modified spectral representation method are studied to simulate multidimensional cross-correlation fluctuating wind loads acting on the transmission tower structure. After widely investigating the characteristic of the downburst, the mechanism model of downburst is studied, a deterministic-stochastic hybrid downburst model and the loads simulating method of this model are proposed to provide the practicable loads for elastic-plastic dynamic analysis of the transmission tower under the action of hurricane.A number of steel specimens were tested to get the hysteretic curve under different plastic strain amplitude in order to calculate respective amplitude’s ultimate cyclic number and ultimate plastic strain energy. The descending rule of specimen’ stiffness during cyclic process is also studied. For several drawbacks of the widely used damage models, steel component’s failure model based on low-cycle fatigue s-n curve is proposed and then verified by low-cycle fatigue tests of many specimens. The experimented results of cyclic tension-compression of steel shows that the proposed models can accurately describe the failure process of the member and several drawbacks of the widely used damage models are improved.Combining with the failure criterion based on low-cycle fatigue s-n curve, the elastic-plastic dynamic analysis method of the cable-structure mixed system under the action of downburst is studied, and the collapse process of tower is displayed under the action of downburst. All of this laid a solid foundation for the research of damage mechanism and failure process of transmission tower.Based on the fatigue cumulative damage theory, the real time crack initiation fatigue life evaluation method in wind-induced transmission tower’s safe warning is proposed. By "identifying real time wind loading acted on the transmission tower by structure’s safe warning system--obtaining the element’s stress response time history by analyzing the nonlinear model--calculating each element’s wind-induced real time cumulative damage" and "classifying the wind loading of the structure on site into many levels by its intensity--calculating probability characteristic of wind’s appearance--evaluating crack initiation fatigue life", the real time residual crack initiation fatigue life is evaluated.更多还原