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A downburst is one of the high-intensity winds that cause transmission tower failures. In recent years, downbursts have brought great disasters to the economies and lives of people all around the world. In this paper, the dynamic stability of the transmission tower-line system under a downburst is analyzed. The deterministic-random mixed model is used to generate the downburst wind field and ANSYS software is employed to establish the finite element model of the transmission tower-line system. The response characteristics of the transmission tower-line system in the downburst and the atmospheric boundary layer (ABL) wind fields are compared through time history analysis. The displacement response of the transmission tower is analyzed with different Zmax values and attack angles. Based on the Budiansky–Roth criterion and dynamic incremental method, the dynamic stability of the transmission tower system under the action of the downburst wind field is studied, and the corresponding wind speed conditions when the transmission tower-line system is unstable are obtained. The results show that the top displacement of the tower-line system under the action of a downburst is 1.83 times that under the ABL wind. The tower top acceleration under the downburst is 1.57 times that under ABL wind. The most unfavorable wind attack angle for a transmission tower-line system is 90°. When Zmax is within the height range of the transmission tower, the influence on the displacement of the transmission tower increases with the increase in Zmax. When Zmax exceeds the height range of the transmission tower, the influence on the displacement of the transmission tower decreases. Under the most unfavorable wind attack angle, the influence of the conductor on the stability of the transmission tower is obvious. [ABSTRACT FROM AUTHOR]

Рассмотрены аварийные ситуации и причины их возникновения на некоторых антаркти­чес­ких станциях. Показано, что в регионе Антарктики скорость ветра может достигать значений в 50–90 м/сек. Эта нагрузка может оказывать значительное влияние на резервуары с нефтепродуктами, кото­рые установлены вне помещений. Проведен анализ причин выхода подобных резервуаров из строя. Для примера рассмотрен резервуар с Украинской антарктической станции Академик Вернадский. Пока­зано, что рассмотренный резервуар находится в неблагоприятных климатических условиях, которые со временем могут привести к аварийным ситуациям. Предложено средство пассивной защиты от ветровой нагрузки. Проанализированы результаты имитационного моделирования в программном комплексе ANSYS. Рассмотрены поля скоростей и давлений. На примере резервуара с Украинской антарктической станции Академик Вернадский показана эффективность предложенного средства пассивной защиты резервуаров от ветровой нагрузки.

A downburst is one of the high-intensity winds that cause transmission tower failures. In recent years, downbursts have brought great disasters to the economies and lives of people all around the world. In this paper, the dynamic stability of the transmission tower-line system under a downburst is analyzed. The deterministic-random mixed model is used to generate the downburst wind field and ANSYS software is employed to establish the finite element model of the transmission tower-line system. The response characteristics of the transmission tower-line system in the downburst and the atmospheric boundary layer (ABL) wind fields are compared through time history analysis. The displacement response of the transmission tower is analyzed with different Zmax values and attack angles. Based on the Budiansky–Roth criterion and dynamic incremental method, the dynamic stability of the transmission tower system under the action of the downburst wind field is studied, and the corresponding wind speed conditions when the transmission tower-line system is unstable are obtained. The results show that the top displacement of the tower-line system under the action of a downburst is 1.83 times that under the ABL wind. The tower top acceleration under the downburst is 1.57 times that under ABL wind. The most unfavorable wind attack angle for a transmission tower-line system is 90°. When Zmax is within the height range of the transmission tower, the influence on the displacement of the transmission tower increases with the increase in Zmax. When Zmax exceeds the height range of the transmission tower, the influence on the displacement of the transmission tower decreases. Under the most unfavorable wind attack angle, the influence of the conductor on the stability of the transmission tower is obvious.

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When compared with horizontal-axis wind turbines, vertical-axis wind turbines (VAWTs) have the primary advantages of insensitivity to wind direction and turbulent wind, simple structural configuration, less fatigue loading, and easy maintenance. In recent years, large-scale VAWTs have attracted considerable attention. Wind loads on a VAWT must be determined prior to structural analyses. However, traditional blade element momentum theory cannot consider the effects of turbulence and other structural components. Moreover, a large VAWT cannot simply be regarded as a planar structure, and 3D computational fluid dynamics (CFD) simulation is computationally prohibitive. In this regard, a practical wind load simulation method for VAWTs based on the strip analysis method and 2D shear stress transport (SST) k-ω model is proposed. A comparison shows that the wind pressure and aerodynamic forces simulated by the 2D SST k-ω model match well with those obtained by 2.5D large eddy simulation (LES). The influences of mean wind speed profile, turbulence, and interaction of all structural components are considered. A large straight-bladed VAWT is taken as a case study. Wind loads obtained in this study will be applied to the fatigue and ultimate strength analyses of the VAWT in the companion paper.

ETFE (ethylene-tetrafluoroethylene) cushion structures have been widely used as building roofs and façades in recent years. However, mechanical behaviors and structural performance of ETFE cushions in cold regions have not been well-understood, which limits its applications in such regions. This paper is thus aimed to study the behaviors of ETFE cushion structures subjected to wind loads at low temperatures. To this end, a novel method of simulating static wind loads was proposed, by pumping out air from the load simulation chamber (LSC) and blowing air into the LSC, generating wind suction and pressure loads, respectively. These simulated wind loads were directly acted on the inner layers of the ETFE cushions in the normal direction. In this case, a corresponding experimental system, integrating ETFE cushion model, load simulation device, environment simulation subsystem, automatic pressure control subsystem and measurement subsystem, was designed and manufactured. Destructive tests of three ETFE cushion models were performed under progressive wind suction loads at 0 °C, −25 °C and −50 °C, respectively. Temperature, internal pressure, deformation, ultimate bearing capacity and failure mode were obtained and analyzed. Experimental results demonstrate that low temperature environment leads to smaller deformation, larger ultimate bearing capacity, larger failure stress and higher frangibility for the ETFE cushion structures. Such insights gained from experimental observations are useful for the analysis and optimal design of ETFE cushion structures in cold regions. [ABSTRACT FROM AUTHOR]

When compared with horizontal-axis wind turbines, vertical-axis wind turbines (VAWTs) have the primary advantages of insensitivity to wind direction and turbulent wind, simple structural configuration, less fatigue loading, and easy maintenance. In recent years, large-scale VAWTs have attracted considerable attention. Wind loads on a VAWT must be determined prior to structural analyses. However, traditional blade element momentum theory cannot consider the effects of turbulence and other structural components. Moreover, a large VAWT cannot simply be regarded as a planar structure, and 3D computational fluid dynamics (CFD) simulation is computationally prohibitive. In this regard, a practical wind load simulation method for VAWTs based on the strip analysis method and 2D shear stress transport (SST) k-ω model is proposed. A comparison shows that the wind pressure and aerodynamic forces simulated by the 2D SST k-ω model match well with those obtained by 2.5D large eddy simulation (LES). The influences of mean wind speed profile, turbulence, and interaction of all structural components are considered. A large straight-bladed VAWT is taken as a case study. Wind loads obtained in this study will be applied to the fatigue and ultimate strength analyses of the VAWT in the companion paper. [ABSTRACT FROM AUTHOR]