输电塔风致响应数值模拟研究进展

Progress in Numerical Simulation Study of Wind-Induced Response of Transmission Towers

输电塔是输电线路中重要的承重设施,其结构安全性直接关系到国家电网和输电线路的正常运行。目前针对输电塔风致响应主要通过现场实测、风洞试验和数值模拟等方法进行研究。随着计算机技术和数值方法的发展,对输电塔风致响应特征进行数值模拟分析开始被广泛应用并取得了大量研究成果。相关的数值模拟研究先通过建立对应的风荷载模型和结构模型,然后以有限元方法分析结构动力响应特征和研究对应的风振控制方法,因此从风荷载模型、结构模型、动力响应特征和风振控制研究等方面总结输电塔风致响应数值模拟研究进展。近地面风场的平均风和脉动风模型是构建结构风荷载的基础。针对平均风主要采用指数型和对数型风速剖面模型,而脉动风则主要根据相关的脉动风谱进行模拟。在不同极端气象条件下,风场表现出不同于良态风的风场特征,对应的平均风和脉动风模型需要进一步根据实际情况研究。构建输电塔风荷载还需要结合相关的结构参数,其中塔体结构整体挡风效应以及塔体构件之间的遮挡效应可通过流场模拟进行分析研究。对输电塔塔体结构建立有限元模型时,通常可将之视为刚架结构和桁梁混合结构,而利用桁架结构进行模拟的误差较大。输电塔所承受的荷载除了风荷载等外部环境荷载外,还应考虑输电线对塔体结构作用带来的影响,因此需建立塔线耦合体系对实际输电线路中塔体结构特征进行模拟。在构建塔线体系有限元模型过程中,可结合悬链线理论和导线水平张力对导线进行建模和找形。基于风荷载模型和结构模型可进行塔体风致响应分析,结构动力特征会对风致响应产生重要的影响,其中导线对塔体的作用使得整体体系的结构动力特征更加复杂。对于不同来流风向条件下输电塔的风荷载,我国相关规范有对应的计算系数和分配系数,而在塔线耦合体系中,风向对塔体结构风致响应的影响更显著。根据是否需要外界能量输入,结构风振控制分为主动控制、被动控制和混合控制。迄今为止,被动控制特别是调谐质量阻尼器仍然是对输电塔风振控制的主要方法,其中阻尼器的自振频率应与塔体自振频率保持一致,风振控制效果才能达到最佳,但是塔线耦合作用使得风振控制的优化更为复杂。此外,还对未来可能的研究方向进行了展望,进一步研究特殊天气风场特征、开发更可靠的有限元建模方法、深入研究塔体扭转向及沿线向响应特征、优化TMD设计参数和布置方案等都应是未来重要的研究方向。

Transmission tower is an important load-bearing facility of transmission line,and its safety is directly related to the normal operation of the national grid and transmission line.Wind-induced response of transmission towers is mainly studied by field measurement,wind tunnel test and numerical simulation.With the development of computer technology and numerical methods,numerical simulation analysis on wind-induced response of transmission towers begins to be widely adopted and significant achievements were gained.Wind load model and structure model are established,then the structure dynamic response characteristics and the corresponding wind vibration control method are studied in related numerical simulation research,so progress of wind-induced response numerical simulation research of transmission tower is summarized from wind load model,structure model and dynamic response characteristics and wind vibration control research in this article.The mean wind and fluctuating wind model of wind field in the ground layer is the basis of building structure wind load.The wind speed profile model used for the mean wind mainly includes exponential and logarithmic wind speed profile model,while the fluctuating wind is mainly simulated according to turbulent wind power spectrum.Under different extreme weather conditions,wind field shows different characteristics from normal wind.The corresponding mean and fluctuating wind models need to be further studied according to the actual situation.The wind load of transmission tower also needs relevant structural parameters,in which the wind resistance effect of tower structure and the shielding effect between tower components can be studied by flow field simulation.When building the transmission tower finite element model,the transmission tower can be regarded as the rigid frame structure and the truss-beam structure,while the error of simulation by using the truss model is large.In addition to wind load and other external environmental loads,the influence of transmission line on tower structure should also be considered,so the tower-line coupling system should be established to simulate the actual structure characteristics of transmission tower.In the process of building the finite element model of tower-line system,the catenary theory and the horizontal tension of conductor can be used to model and shape the conductor.Based on the wind load model and the structural model,the wind-induced response of transmission tower can be analyzed.The dynamic characteristics of the structure have important effects on the wind-induced response,and the effect of the conductor on the tower makes dynamic characteristics of tower-line system more complex.For the wind load of tower under different wind direction,the relevant codes have corresponding calculation coefficient and distribution coefficient.For the tower-line coupling system,the wind direction has more significant effects on the wind-induced response.According to whether external energy input is needed,wind-induced vibration control can be divided into active control,passive control and hybrid control.So far passive control,especially tuned mass damper,is still the main method for wind-induced vibration control of transmission tower.The natural frequency of damper should be consistent with the natural frequency of tower,then the windinduced vibration control works best.However,the optimization of wind-induced vibration control is more complicated due to tower-line coupling effect.Besides,future research direction was prospected.Further research on wind field characteristics of special weather,development of more reliable finite element modeling methods,further study of tower torsional and along-line response characteristics,and optimization of TMD design parameters and layout should be important research directions in the future.