Software to aid in the detailed design of tall post-tensioned concrete wind turbine towers

Van Schalkwyk, Derrick (2017-03)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: In engineering practice, the process associated with the detailed design of wind turbine towers is often an overwhelming task. This is particularly the case when using sophisticated Finite Element Method (FEM) software to model and analyse wind turbine towers, as these packages generally have significant computational modelling requirements. The aim of this study is to design custom software specific to tall post-tensioned concrete wind turbine towers, to aid in the detailed design process. Focus is placed on designing software to be computationally inexpensive and user friendly, while still being able to produce accurate analysis results. To do this, a simplified two-dimensional finite element model, only consisting of 4 Degree of Freedom (DOF) beam elements, is used to represent the wind turbine tower. Although the tower model is simplified significantly, the complexity of the tower is captured using a composite cross section model, which is able to consider nonlinear material properties. The cross section analysis methodology is also designed to consider the effects of internal post-tensioning applied to the tower. A FEM modal analysis is implemented to calculate the tower frequencies. The model is also analysed using the Stiffness Method and Moment Area Method to obtain tower deflections. Furthermore, iterative numerical approaches are presented in conjunction with these analysis techniques to consider second order effects. By integrating the cross section analysis methodology with the structural analysis techniques, accurate beam element properties, normal stresses and deflections are calculated. Various case studies are included in this study using the developed methodology and compared to results obtained from literature or existing software as verification. The tests are conducted using a graphical user interface (GUI). The GUI is designed to guide the user through the entire process of analysing a Wind Turbine Generator (WTG) tower, aiding in the model setup, generation of loads on the tower, performing analyses and providing relevant analysis output information. It has been found that the implemented analysis techniques yield accurate results while significantly less computational effort is expended when compared to sophisticated FEM software.

AFRIKAANSE OPSOMMING: In die ingenieurspraktyk is die gedetailleerde ontwerp van windturbine torings dikwels 'n oorweldigende taak. Dit is veral die geval wanneer gesofistikeerde Eindige Element sagteware gebruik word om windturbine torings te modelleer en analiseer, omdat hierdie pakette hoë numeriese modellering vereistes het. Die hoofdoel van hierdie projek is om sagteware te ontwerp om ondersteuning te bied tydens die gedetailleerde ontwerp proses van hoë nagespande beton windturbine torings. Fokus word geplaas op die ontwerp van gebruikersvriendelike sagteware met relatiewe lae numeriese modellering vereistes, terwyl dit steeds in staat is om akkurate resultate te lewer. Vir hierdie doel is 'n vereenvoudigde tweedimensionele eindige element model, wat slegs bestaan uit balk elementemet vier vryheidsgrade elk, ontwikkel om ‘n windturbine toring te modelleer. Hoewel die toring model aansienlik vereenvoudig is, is die kompleksiteit van die toring vasgevang met behulp van 'n saamgestelde dwarssnit model, wat in staat is om nie-lineêre materiaaleienskappe in ag te neem. Die dwarssnit analise metodiek is ook ontwerp om die effek wat interne voorspanning op ‘n toring het in ag te neem. ‘n Eindige Element Metode (EEM) modale analise is geïmplementeer om die toring frekwensies te bereken. Die model is ook geanaliseer met behulp van die Styfheidsmetode en Moment Area Metode om toring defleksies te bepaal. Verder word iteratiewe, numeriese benaderings beskryf wat geïntegreer word met bogenoemde analisetegnieke om tweede orde effekte in ag te neem. Deur die integrasie van die dwarssnit analise metode met die struktuuranalise tegnieke, kan akkurate balk element eienskappe, normaalspannings en defleksies bereken word. Verskeie gevallestudies is ingesluit in hierdie studie met die doel om die ontwikkelde metodiek se resultate te vergelyk met dié verkry vanuit die literatuur of bestaande sagteware. Die toetse word uitgevoer met behulp van 'n grafiese gebruikerskoppelvlak. Die koppelvlak is ontwerp om die gebruiker te lei deur die hele ontwerpproses van die windturbine toring, insluitende die opstelling van die model, die plasing van laste op die toring, die uitvoering van analieses en die verskaffing van relevante analiese resultate. Daar is gevind dat die geïmplementeerde analisetegnieke akkurate resultate lewer, terwyl die ontwikkelde sagteware aansienlik minder tyd en numeriese vereistes het in vergelyking met gesofistikeerde EEM sagteware.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100942
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