Seismic response of a full-scale wind turbine tower using experimental and numerical modal analysis (original) (raw)
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Dynamic Behavior of A Full-Scale Wind Turbine Tower Under Seismic Loading
—This paper presents the dynamic investigation of an existing wind turbine tower. Both experimental and numerical analyses were performed to assess the structural response of the tower under seismic load. Field ambient vibration test was applied to identify the actual dynamic properties experimentally. A vibration based finite element model was built in ANSYS to conduct the seismic response analysis. The tower shown to survive moderate earthquakes as it is located in Zafarana wind farm in Egypt, a zone lies by the red sea known for its historical seismic activity.
Structure and Infrastructure Engineering, 2016
The response of wind turbines is induced by dynamic loads such as wind, transient and cyclic loads, and also extreme loads such as earthquakes. Thus, the structural design requires an accurate evaluation of the modal parameters of the system because it is strongly required that no resonances are excited. Moreover, it has been concluded from previous research works that soil-structure interaction (SSI) should be accounted for the analysis. In the present paper, the structural dynamic response of wind turbine towers is investigated considering different soil conditions using a numerical model. This research is focused on SSI effects. Firstly, changes in the modal parameters of three different wind turbines considering the effect of three soils are evaluated. The results show that the evaluation of the natural frequency and the resulting classification of the wind turbine design type can be affected by SSI. The obtained results could be used to evaluate the decrement of the natural frequency of the wind turbine account for the soil and the foundation in relation to the frequency computed without soil interaction. Next, the seismic response of the wind tower is analysed considering two seismic events: a horizontally polarized shear (SH) incident wave and El Centro earthquake.
A numerical study of wind-induced tower vibrations
Computers & Structures, 1987
The application of the finite element method for the analysis of wind-induced tower vibrations is presented and discussed. In this study simulated wind forcing functions were applied to a 3-D model of an existing illumination tower, and its response was studied under various loading conditions. The obtained numerical results are compared with experimental data for evaluating the accuracy of this approach. NOTATION area on which wind forces act parameter for relating wind velocity with height shape factor, or force factor damping matrix drag coefhcient lift coefficient dimension of body normal to wind flow tower diameter elastic modulus force structural response frequency vortex shedding frequency stitTness matrix mass matrix forcing function vector dynamic head of wind Reynolds number Strouhal number time wind speed kinematic viscosity of air acceleration, velocity and displacement vectors, respectively elevation of points at which wind speed is measured, or computed mass density of air vortex shedding circular frequency
Static, seismic and stability analyses of a prototype wind turbine steel tower
Engineering Structures, 2002
Selected results of a study concerning the load bearing capacity and the seismic behavior of a prototype steel tower for a 450 kW wind turbine with a horizontal power transmission axle are presented. The main load bearing structure of the steel tower rises to almost 38 m high and consists of thin-wall cylindrical and conical parts, of varying diameters and wall thicknesses, which are linked together by bolted circular rings. The behavior and the load capacity of the structure have been studied with the aid of a refined finite element and other simplified models recommended by appropriate building codes. The structure is analyzed for static and seismic loads representing the effects of gravity, the operational and survival aerodynamic conditions, and possible site-dependent seismic motions. Comparative studies have been performed on the results of the above analyses and some useful conclusions are drawn pertaining to the effectiveness and accuracy of the various models used in this work.
Seismic Analysis of Wind Turbines
Earthquake Spectra, 2013
An analytical model of an operating wind turbine to obtain the seismic response due to three base accelerations is presented. The model considers the flexibility of the blades in the flapping direction and the flexibility of the tower in bending and twisting. Blade aerodynamics and gyroscopic moments are included. A Vestas-V82 turbine is selected to demonstrate the methodology. The results show that only the first two tower modes in each direction (fore-aft and lateral) are mostly excited. It is found that the lateral motion of the wind turbine is more susceptible to experiencing large displacements since the aerodynamic effects are negligible in this direction. The stresses due to combined operational and seismic loads and due to extreme wind loads are less than the allowable stresses. The stresses calculated at the tower top section due to combined operational and seismic loads are larger than those due to extreme wind loads.
Structural performance of a parked wind turbine tower subjected to strong ground motions
Engineering Structures, 2016
The objective of this paper is to evaluate the structural performance of a typical wind turbine tower subjected to strong ground motions. A detailed finite element model of an 80 m wind turbine tower was developed and subjected to strong ground motions. Two sets of input ground motions were used: one with pulse-type near-fault motions and the other one with far-fault motions. The structural performance of the wind turbine tower was investigated through seismic fragility analysis. The potential limit states were defined as global buckling of the tower, first occurrence of yielding, overturning of the foundation and permanent deformation of the tower. It was found that the wind turbine tower investigated in this study is most vulnerable to the overturning in the event of an earthquake. Yielding of the tower is the second most probable failure mechanism, which is followed by development of permanent deformation and global buckling of the tower. Similar trends in the failure mechanism were observed for both near-fault and far-fault ground motions.
Considerations for the structural analysis and design of wind turbine towers: A review
Renewable and Sustainable Energy Reviews, 2021
The use of wind generators has grown exponentially in recent decades to meet the increasing demand for electricity. With both generator design and generation capability growing, the resulting increases in the size of generators require them to withstand multiple and intense dynamic loads. These loads cause greater stresses, fatigue, torsions, deflections, and vibrations, among others, leading to greater failures during a generator's life cycle. These issues are of great significance to the research and technological development involved in improving the design, manufacturing process, and installation of wind turbine towers. This work presents a detailed review of the most notable aspects involved in the analysis and design of towers. These aspects include loads and actuating forces, types of structural analysis, used software, and types of experiments used for validating the aspects themselves. In addition, different perspectives regarding the types of supports for onshore and offshore wind turbines are discussed. Likewise, the proposals for new designs and construction materials are also analyzed. The present review integrates the most relevant aspects and recent developments in the design, manufacture, and installation of wind turbine towers. This has been carried out with the objective of providing a contemporary frame of reference that will facilitate the future research and project development related to wind turbine towers.
Nigerian Journal of Technology (NIJOTECH), 2017
Renewable energy sources have gained much attention due to the recent energy crisis and the urge to get clean energy. Among the main options being studied, wind energy is a strong contender because of its reliability due to the maturity of the technology, good infrastructure and relative cost competitiveness. It is also interesting to note that there are physical limits to the potential height of a wind turbine tower since the mechanical structure of wind turbines are thus very flexible and tend to oscillate. This makes the design of wind turbines a demanding task. In this paper, the oscillation of a wind turbine tower due to imbalance in the masses of the blades is modeled in maplesim and the effect of the tower height on its oscillation was simulated. For a wind turbine with three rotor blades, two of which have masses of 10 kg, a mass moment of inertia of approximately 20 kg/m 2 and one of the blades has a moment of inertia which is 1% less than the other blades. The simulation showed the most stable system for the most energy capture for this case study to be a rotor speed of 5.5rad/s at a height of 10m. At this angular frequency the deflection of the top of the wind turbine was approximately 1mm.
Numerical modal analysis of a 850 KW wind turbine steel tower
International Review of Applied Sciences and Engineering
The study deals with the numerical analysis aspects that are necessary for identifying of modal parameters of the tower structure as the most important part of the horizontal axis wind turbine, which are basic for the dynamic response analysis. In the present study, the modal behavior of an actual 55-m-high steel tower of 850 KW wind turbine (GAMESA G52/850 model) is investigated by using three-dimensional (3D) Finite Element (FE) method. The model was used to identify natural frequencies, their corresponding mode shapes and mass participation ratios, and the suggestions to avoid resonance for tower structure under the action wind. The results indicate that there is a very good agreement with the fundamental vibration theory of Euler-Bernoulli beam with lamped masse in bending vibration modes. When the rotor of the wind turbine runs at the speed of less than or equal to 25.9 rpm it will not have resonant problems (stiff–stiff tower design). Furthermore, in case the rotor runs at the...