Coupling vibration response analysis of wind-train-bridge system considering the train-induced wind effect

Yujing Wang,Weiwei Guo,He Xia,Shanshan Wang,Man Xu 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.3

Considering the wind loads and track irregularity as external excitation, the wind-train-bridge dynamic analysis model considering the longitudinal freedom of train is established in the present study. In the model, the wind load of trainbridge system under the train-induced wind field and the combined wind field is obtained by employing Computational Fluid Dynamics (CFD) method. With the CRH2 high-speed train and a 10-span simply-supported box girder bridge as an example, the whole history of the train running on the bridge under the combined effect of train-induced wind and crosswind is simulated to analyze the dynamic response of the train-bridge system. In addition, the operational safety indicators of the train are evaluated. According to the obtained results, the dynamic response of vehicles and bridges increases with the train speed without the consideration of the crosswind. In the combined wind field, the train-induced wind exerts a greater impact on the dynamic response of the vehicle, but has a less influence on that of the bridge simultaneously. Moreover, the influence of wind velocity is greater than that of train speed. When the wind-train-bridge dynamic response analysis is carried out based on traditional methods, the calculated wind load of the train-bridge system is too high, making the calculated responses too large to be consistent with actual values.

Analysis of Dynamic Response Characteristics for 5 MW Jacket-type Fixed Offshore Wind Turbine

Jaewook Kim,Sanghwan Heo,WeonCheol Koo 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.5

This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.

Dynamic reliability analysis of offshore wind turbine support structure under earthquake

김동현,이기남,이용제,이일근 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.6

Seismic reliability analysis of a jacket-type support structure for an offshore wind turbine was performed. When defining the limit state function by using the dynamic response of the support structure, a number of dynamic calculations must be performed in a First-Order Reliability Method (FORM). That means analysis costs become too high. In this paper, a new reliability analysis approach using a static response is used. The dynamic effect of the response is considered by introducing a new parameter called the Peak Response Factor (PRF). The probability distribution of PRF can be estimated by using the peak value in the dynamic response. The probability distribution of the PRF was obtained by analyzing dynamic responses during a set of ground motions. A numerical example is presented to compare the proposed approach with the conventional static response-based approach.

Wind-induced dynamic response and its load estimation for structural frames of single-layer latticed domes with long spans

Uematsu, Yasushi,Sone, Takayuki,Yamada, Motohiko,Hongo, Takeshi Techno-Press 2002 Wind and Structures, An International Journal (WAS Vol.5 No.6

The main purpose of this study is to discuss the design wind loads for the structural frames of single-layer latticed domes with long spans. First, wind pressures are measured simultaneously at many points on dome models in a wind tunnel. Then, the dynamic response of several models is analyzed in the time domain, using the pressure data obtained from the wind tunnel experiment. The nodal displacements and the resultant member stresses are computed at each time step. The results indicate that the dome's dynamic response is generally dominated by such vibration modes that contribute to the static response significantly. Furthermore, the dynamic response is found to be almost quasi-static. Then, a series of quasi-static analyses, in which the inertia and damping terms are neglected, is made for a wide range of the dome's geometry. Based on the results, a discussion is made of the design wind load. It is found that a gust effect factor approach can be used for the load estimation. Finally, an empirical formula for the gust effect factor and a simple model of the pressure coefficient distribution are provided.

Probability density evolution analysis on dynamic response and reliability estimation of wind-excited transmission towers

Zhang, Lin-Lin,Li, Jie Techno-Press 2007 Wind and Structures, An International Journal (WAS Vol.10 No.1

Transmission tower is a vital component in electrical system. In order to accurately compute the dynamic response and reliability of transmission tower under the excitation of wind loading, a new method termed as probability density evolution method (PDEM) is introduced in the paper. The PDEM had been proved to be of high accuracy and efficiency in most kinds of stochastic structural analysis. Consequently, it is very hopeful for the above needs to apply the PDEM in dynamic response of wind-excited transmission towers. Meanwhile, this paper explores the wind stochastic field from stochastic Fourier spectrum. Based on this new viewpoint, the basic random parameters of the wind stochastic field, the roughness length $z_0$ and the mean wind velocity at 10 m heigh $U_{10}$, as well as their probability density functions, are investigated. A latticed steel transmission tower subject to wind loading is studied in detail. It is shown that not only the statistic quantities of the dynamic response, but also the instantaneous PDF of the response and the time varying reliability can be worked out by the proposed method. The results demonstrate that the PDEM is feasible and efficient in the dynamic response and reliability analysis of wind-excited transmission towers.

Numerical simulation on the typhoon-induced dynamic behavior of transmission tower-line system

Yunzhu Cai,Jiawei Wan,Qiang Xie,Songtao Xue 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.4

The spatiotemporal impact of typhoons moving across transmission networks is increasingly evident, which may result in the failure of the overhead transmission tower-line (TL) system. The structural design and safety assessment to transmission TL systems that subjected to extreme winds are necessary. This paper aims to provide fundamental insights on the wind field caused by typhoons as well as the typhoon-induced dynamic loads and responses of the transmission TL system, by means of the numerical simulation. This paper offers a numerical scheme to simulate the typhoon-induced wind field on a TL system, in which the movement of the typhoon center and the nonstationary fluctuation of the wind are concerned. In the scheme, the near-surface mean wind speed is calculated based on the radial profile and translation of storms; the nonstationary fluctuation component is generated by a time-varying modulation function. By applying the simulated wind field to the finite element model of TL system, we yield the dynamic responses of the TL system as well as the dynamic loads resulting from the interaction between the structure and wind. Utilizing the evolutionary power spectral density (EPSD) function, the fluctuating wind loads and structural responses are addressed both in the time and frequency domains. Further discussion is done on the typhoon-induced loads by constructing the dynamic equivalent factors. The time-varying equivalent factors show the stationary process, which demonstrates the fading out of the non-stationarity for simulated wind loads. The comparison result indicates that the gust response factor of tower recommended by design codes may not be safe enough when the typhoon impact is concerned.

Dynamic reliability analysis of offshore wind turbine support structure under earthquake

Kim, Dong-Hyawn,Lee, Gee-Nam,Lee, Yongjei,Lee, Il-Keun Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.6

Seismic reliability analysis of a jacket-type support structure for an offshore wind turbine was performed. When defining the limit state function by using the dynamic response of the support structure, a number of dynamic calculations must be performed in a First-Order Reliability Method (FORM). That means analysis costs become too high. In this paper, a new reliability analysis approach using a static response is used. The dynamic effect of the response is considered by introducing a new parameter called the Peak Response Factor (PRF). The probability distribution of PRF can be estimated by using the peak value in the dynamic response. The probability distribution of the PRF was obtained by analyzing dynamic responses during a set of ground motions. A numerical example is presented to compare the proposed approach with the conventional static response-based approach.

Response of double hinged articulated tower platforms to wind forces

Islam, Nazrul,Zaheer, Mohd Moonis,Ahmed, Suhail Techno-Press 2009 Wind and Structures, An International Journal (WAS Vol.12 No.2

Articulated tower platforms due to its compliant nature are more susceptible to the dynamic effects of wind than conventional fixed platforms. Dynamic response analysis of a double hinged articulated tower excited by low frequency wind forces with random waves is presented in this paper. The exposed super structure of the platform, housing the drilling and production facilities is subjected to mean and fluctuating wind loads, while the submerged portion is acted upon by wind driven waves. The fluctuating component of the wind velocity is modeled by Emil Simiu's spectrum, while the sea state is characterized by Pierson-Moskowitz spectrum. Nonlinearities in the system due to drag force, added mass, variable submergence and instantaneous tower orientation are considered in the analysis. To account for these nonlinearities, an implicit time integration scheme (Newmark's-${\beta}$) has been employed which solves the equation of motion in an iterative fashion and response time histories are obtained. The power spectra obtained from random response time histories show the significance of low frequency responses.

Dynamic Wind Response of Twin Tall Buildings Linked by a Skybridge

Lim Juntack 한국풍공학회 2019 한국풍공학회지 Vol.23 No.3

스카이브릿지로 연결된 쌍둥이 초고층건물은 두 가지 종류의 연동성-스카이브릿지로 인해 두 건물의 거동 동기화를 유발하는 구조적 연동성과 작용하는 풍하중의 높은 상관성으로 인한 공기역학적 연동성-이 나타난다. 단일 건물에 널리 적용되는 전통적인 풍력실험 방법으로는 이런 연동성과 영향들을 완벽히 파악할 수 없는 실정이다. 그런 이유로 보다 발전된 동적 풍응답 해석법이 요구된다. 이 논문은 스카이브릿지로 연결된 쌍둥이 건물에서 발생하는 구조적 및 공기역학적인 연동성을 다룰 수 있는 듀얼 풍력실험 방법을 자세히 다루었다. 제안된 방법을 적용하여 건물의 풍가속도에 대한 구조적 및 공기역학적 연동성의 영향을 평가하였다. 건물의 풍응답 산정에 스펙트럼 적분법과 백색 소음 근사법을 적용하였다. 실험 및 결과로 볼 때 동적 풍응답에 상당한 영향이 있음을 확인할 수 있었다. 여러 개의 풍력 측정센서를 활용한 풍력실험 기술은 구조적으로 연결된 초고층건물에 대한 풍동실험에 유용하게 사용될 것으로 판단된다. Twin tall buildings linked a skybridge involve two types of coupling: the structural coupling, developed by a skybridge, synchronizing the motions of vibration of the two building and the aerodynamic coupling resulting from high cross-correlations of the components of wind loading. From the wind engineering viewpoint, an understanding of these couplings and their impacts on the wind-induced response of the buildings can not be fully accounted for when using the traditional high-frequency force balance (HFFB) approach tailored for single tall buildings, and thus this requires utilization of advanced dynamic wind response analysis. This paper addresses the dual- HFFB approach accounting for correlated wind loading and structurally coupled response of twin buildings with a skybridge. The proposed method is subsequently used to investigate the effects of aerodynamic and structural couplings on the rooftop accelerations of the buildings. Spectral integration and white-noise approximation approaches are employed in calculations of the building responses. The presented results show significant effects of both the aerodynamic and structural couplings. The multi-HFFB technique would be useful for wind tunnel study of structurally connected tall buildings.

Response of double hinged articulated tower platforms to wind forces

Nazrul Islam,Mohd Moonis Zaheer,Suhail Ahmed 한국풍공학회 2009 Wind and Structures, An International Journal (WAS Vol.12 No.2

Articulated tower platforms due to its compliant nature are more susceptible to the dynamic effects of wind than conventional fixed platforms. Dynamic response analysis of a double hinged articulated tower excited by low frequency wind forces with random waves is presented in this paper. The exposed super structure of the platform, housing the drilling and production facilities is subjected to mean and fluctuating wind loads, while the ubmerged portion is acted upon by wind driven waves. The fluctuating component of the wind velocity is modeled by Emil Simiu’s spectrum, while the sea state is characterized by Pierson-Moskowitz spectrum. Nonlinearities in the system due to drag force, added mass, variable submergence and instantaneous tower orientation are considered in the analysis. To account for these nonlinearities, an implicit time integration scheme (Newmark’s-β) has been employed which solves the equation of motion in an iterative fashion and response time histories are obtained. The power spectra obtained from random response time histories show the significance of low frequency responses.