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Mutallimov, Turan. "Wind load effect on storage tanks in Azerbaijan." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23576/.
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Oil storage tanks play a significant role in social and economic development in Azerbaijan where is known as an oil producer country; however, there have been various cases of wind and earthquake destruction. The effect of wind disturbance on dynamic responses is analyzed, and the role of storage ratio and seismic waveform on dynamic responses under wind-earthquake activity is investigated further. The results show that the wind disruption effect has a significant impact on the dynamic responses of liquid storage tanks, especially in the empty state. When the liquid storage level is high, traditional oil storage tanks are easily destroyed by the action of a strong wind. Wind interference effect should be considered in the design and implementation of oil storage tanks, while shock absorption and strengthening steps for oil storage tanks under wind-strong earthquakes should be taken.
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Jones, Scott Alan. "Effect of pruning type, pruning dose, and wind speed on tree response to wind load." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013321.
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Martin, Mogamat Noer. "Optimal placement and effect of a wind farm on load flow and protection systems in a municipal distribution network." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31005.
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Much research has been done on the effects of distributed generation on network characteristics. However, little research has been done on the effects of this distributed generation on current network protection schemes. An IPP has approached a South African municipality regarding the connection of a wind farm that would be connected to the municipality’s existing grid. This presented a unique opportunity to simulate and study the impact and effect that this wind farm would have on a real-life network in terms of network operation and protection schemes. This also presents the possibility of connecting the wind farm in a different configuration, possibly resulting in better network operation at a lower cost. The network optimisation in this research was done using the probability-based incremental learning (PBIL) and differential evolution (DE) optimisation techniques. These algorithms were programmed and modelled according to the desired IPP wind farm requirements using the MATLAB and MATPOWER simulation packages. The networks used in these algorithms were modelled in the text-based MATPOWER format. This research goes on to study a modified 14-bus IEEE test network in terms of network characteristics and protection performance so that an idea of the performance of the optimisation algorithms can be obtained. Protection data for the IEEE network was not available. The network was thus graded for use in this study. The research then continues to model the existing and proposed network configuration, and proposes various other points of connection to the municipal network using the PBIL and DE algorithms. These studies were conducted using the DIgSILENT PowerFactory simulation package, with the networks and protection data being modelled in this package. Network and protection performance results were recorded for each case in both networks under study. The results show that in the case of the modified IEEE network, the DE algorithm provides a better solution in terms of improving power losses while the PBIL algorithm provides a better solution in terms of improving the voltage profile. In the case of the municipality network, the DE algorithm provides the best performance, with the DE result managing to reduce power losses by 83.89% compared to the current and proposed network configurations. The overall voltage profile was also seen to improve by over 23%. The research also found that the change in fault level for the various cases are minimal. This is due to the limitation in fault current contribution imposed by the use of an inverter system connecting the wind farm to the grid. This means that, as the results shows, network grading is not very much affected by the addition of the wind farm connections. However, it is seen that the municipal network is not optimally graded in the base case. Finally, it is also seen that, though not often used in research, the MATPOWER package works well as a network simulation tool. A costing analysis was also conducted and shows that the DE solution is the most cost-effective solution, in addition to being the best-performing solution. The study recommends that the results produced by the DE algorithm be implemented instead of the proposed implementation. The municipal network should also be regraded and new protection settings should be implemented.
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AYME, CARRIE NATHALIE. "Analyse des effets du vent sur les structures baties : constructions basses et structures elancees." Nantes, 1987. http://www.theses.fr/1987NANT2051.
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Methode de calcul d'une force statique equivalente pour representer l'action du vent sur une structure basse type (halle industrielle), avec determination de coefficients de pression dans une approche reglementaire. Pour les structures elevees, ou l'aspect dynamique est preponderant, developpement d'un logiciel a partir du modele vickery-basu (structure elancee a section circulaire); determination des parametres aerodynamiques a partir de donnees experimentales
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Lemoult, Bernard. "Contribution a la connaissance des actions du vent sur les batiments a structure metallique." Poitiers, 1988. http://www.theses.fr/1988POIT2201.
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Etude experimentale a echelle reduite dans une soufflerie a couche limite (cstb, nantes), pour determiner le champ de pression; le role de la turbulence du vent amont sur les sollicitations extremes sur un batiment a ossature metallique est souligne
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Woldemikael, Biruk Worku. "Effects of cracking of coupling beams onhigh rise towers subjected to wind load." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290589.
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In high rise towers, reinforced concrete elevator shafts with coupling beams are extensively used as a principal structural element to resist lateral loads. The lateral load resistance of the tower is dominantly dependent on the stiffness of the load-bearing walls, and coupling beams connecting them. In an interest to study the reduction in the stiffness of high rise tower due to cracking in the coupling beams, variability in the reinforcement content, concrete grade and the effect of joint flexibility at the beam-wall intersection, this master thesis presents the analytical and finite element approaches to determine the equivalent height of the concrete coupling beams and the overall global stability of the high-rise tower. A comprehensive parametric study on 240 combinations of reinforced concrete coupling beams and 48 models of the global tower has been carried out to backtrack the effective stiffness of the RC coupling beams from the load-deflection curve. As a result, the stiffness and the equivalent height of coupling beams are computed and plotted as a function of the concretegrade, reinforcement content and aspect ratio. Additionally, the tip deflections of the towers for both the cracked & reinforced and un-reinforced & un-cracked models are also plotted as functions of the concrete grade, reinforcement content and aspect ratio.The obtained results show that the stiffness ratio and the ratio of the equivalent height to the normal height increase with the increase in the longitudinal reinforcement ratio and aspectratio but decrease with an increase in the concrete grade for both analytical and finite element methods. The tip deflection of tower is not significantly affected by an increase in the reinforcement content of slender coupling beams and vice versa for both the analytical and the finite element method. Independently of the slenderness of the composing coupling beams, the stiffness increases significantly with an increase in the concrete grade. These results show a good picture on how to choose the equivalent height in the model with no reinforcement. So, the developed diagram will be a more practical method for the designer of awhole building at the early stage design. Thick coupling beams need to be reinforced to reach the gross section’s stiffness while slender sections will have a higher stiffness with reinforcement. This would help the designer to find a more rational model without reinforcement. Using Hans Petersson’s analytical method, regarding the joint flexibility at the beam wall intersection, to exploit the full capacity of a concrete coupling beam section, the stiffness should be reduced. For global models, independently of the slenderness of the composing coupling beams, the stiffness increases significantly with an increase in the concrete grade.I höghus används hisschakt av armerad betong tillsammans med kopplingsbalkar i stor utsträckning som främsta konstruktionselement för att motstå horisontella laster. Tornets horisontella bärförmåga är beroende av analytiska studier och studier med finita element metoden styvheten hos de bärande väggarna, och kopplingsbalkarna som förbinder dem. För att studera minskningen av styvheten i höghustorn på grund av sprickbildning i kopplingsbalkar, variationen i armeringsmängden, betongkvaliteten och effekten av ledflexibilitet vid balk-vägg-knutpunkten, presenterar detta examensarbete kopplingsbalkarnas effektiva styvhet och höghusets globala stabilitet. En omfattande parametrisk studie på 240 olika kombinationer av armerade kopplingsbalkar och 32 modeller av ett höghus har genomförts för att härleda den effektiva styvheten i de armerade kopplingsbalkarna från last-deformationskurvan. Som ett resultat beräknas styvheten och den ekvivalenta höjden av kopplingsbalkarna och plottas som funktion av betongkvaliteten och armeringsmängden. Dessutom modelleras höghuset för både spruckna & armerade kopplingsbalkar samt oarmerade & ospruckna kopplingsbalkar för att erhålla utböjningen av höghusets topp. Resultatet plottas som funktion av betongkvaliteten och armeringsmängden. De erhållna resultaten visar att styvhetsförhållandet och förhållandet mellan ekvivalent höjd till normal höjd ökar med mer längsgående armering och tvärsnittsförhållandet men minskar med en ökning av betongkvaliteten för både den analytiska och finita elementmetoden. Utböjningen av höghusets topp påverkas inte nämnbart av en ökning av armeringsmängden i de slanka kopplingsbalkarna och vice versa för både den analytiska och finita elementmetoden. Oberoende av slankheten av kopplingsbalkarna ökar styvheten betydligt med en ökning av betongkvaliteten. Dessa resultat visar en bra bild på hur man väljer ekvivalent höjd i modellen utan armering. Därmed kommer det framtagna diagrammet vara en mer praktisk metod för att i ett tidigt skede konstruera en hel byggnad. Tjocka kopplingsbalkar måste armeras för att nå tvärsnittets styvhet medan smala tvärsnitt kommer att ha en högre styvhet med armering. Detta skulle hjälpa konstruktören att hitta en mer rationell modell utan armering. Med hjälp av Hans Peterssons analytiska metod, angående ledflexibiliteten vid balk-väggknutpunkten, bör styvheten minskas för att utnyttja den fulla kapaciteten hos en betongkopplingsbalk. För globala modeller, oberoende av de slanka kopplingsbalkarna, ökar styvheten betydligt med en ökning av betongkvaliteten.
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Kayisoglu, Bengi. "Investigation Of Wind Effects On Tall Buildings Through Wind Tunnel Testing." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613324/index.pdf.
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In recent years, especially in the crowded city-centers where land prizes have become extremely high, tall buildings with more than 30 floors have started to be designed and constructed in Turkey. On the other hand, the technical improvements have provided the opportunity of design and construction of more slender structures which are influenced by the wind actions more. If the building is flexible, wind can interact with it so the wind induced oscillations can be significantly magnified. In order to analyze the response of such buildings under wind effects, wind tunnel tests are accepted to be the most powerful tool all over the world. In this study, a series of tests were performed in Ankara Wind Tunnel on a model building in the shape of a rectangular prism. For the similitude of flow conditions, passive devices were designed. The response of the model building was measured through a high frequency base balance which was designed specifically for this case study. Through the tests, the effects of turbulence intensity, vortex shedding and wind angle of attack on the response of the building were questioned. Finally, the results were compared with the results of various technical specifications about wind.
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Al, Tubi Issa. "Effects of variable load and rotational speed conditions on gear micropitting in wind turbine gearboxes." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7173/.
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Micropitting damage is one of the failure modes commonly observed on gears and bearings in wind turbine (WT) gearboxes. It can lead to destructive failures which, in turn, lead to unplanned WT shutdown and expensive replacement. This research provides an insight into effects of variable load and rotational speed condition on micropitting in WT gearboxes. It also investigates in detail the occurrence of micropitting in WT gearboxes under various operational conditions using an experimental study and an analytical study, employing two methods: an analytical method based on selected SCADA (Supervisory Control and Data Acquisition) data and a probabilistic modelling of SCADA data method. This study focuses predominantly on the micropitting of the high speed shaft (HSS) gear of a WT gearbox operating under nominal and varying load and speed conditions. The SCADA datasets recorded from WT gearboxes in operation are used. Based on the SCADA data, the recorded WT generator power output and generator rotational speed are used to obtain the shaft torque of the HSS driven gear. Based on ISO Technical Report ISO/TR 15144-1 (2010) and various ISO gear standards, an analytical study is carried out to assess the risk of gear micropitting by determining the contact stress, sliding parameter, local contact temperature, lubricant film thickness and specific lubricant film thickness along the line of action of the gear tooth contact by considering the WT operating load and speed conditions. The experimental study investigates the initiation and progression of gear micropitting when gear tooth flanks are subjected to varying torque levels at a constant rotational speed. The study is conducted by carrying out gear micropitting testing and surface inspection, as well as validating implementing analytical evaluations by comparing the obtained results with that obtained by using various commercial software packages based on ISO Technical Report ISO/TR 15144-1 and AGMA 925-A03 standard. The surface inspection of tested gears is carried out using procedures of surface roughness measurement, replica of surface micropits and profile deviation measurement. The analytical results are compared to the experimental results to predict the occurrence of gear micropitting through evaluating tooth contact stress, sliding parameter, local contact temperature and specific lubricant film thickness at different points along the gear tooth flank. The surface roughness measurements, obtained from the tested gears after each cycle run under specific torque levels, are considered in the analytical investigation. The gear testing results show that micropitting initiates at the pinion dedendum, but escalates at the addendum because of the greater severity of progressive micropitting at the mating wheel dedendum. The micropitting initiates at the beginning of the tip relief area of the pinion and at the root of the pinion with which the wheel tip relief area first starts to mesh. The analytical results confirm that maximum contact stresses and minimum lubricant film thickness occur at these areas. The lubricant film thickness varies considerably because of changes in surface roughness after the gears undergo various running cycles under varying torque levels. The validation process reveals that the ISO/TR 15144-1 results provide a better correlation with experimental results, as compared to AGMA 925-A03 results. The analysis of WT operational condition using selected one month SCADA data identifies three regions of relationships between the generator power and wind speed, the generator speed and wind speed variations. Non-uniform distributions of contact stress, contact temperature and lubricant film thickness over the tooth flank are observed. This is due to the conditions of torque and rotational speed variations and sliding contact along the gear tooth flanks. The lubricant film thickness varies along the tooth flank and is at its lowest when the tip of the HSS wheel gear engages with the root of the HSS driven gear. The lubricant film thickness increases with the increase of the rotational speed and decreases as the torque and sliding increase. It can be concluded that micropitting is most likely to initiate at the dedendum of pinion gear. The lowest film thickness occurs when the torque is high and the rotational speed is at its lowest, which may cause direct tooth surface contact. In low torque condition, the varying rotational speed condition may cause a considerable variation in lubricant film thickness, thus interrupting the lubrication, which may result in micropitting. Finally, a probabilistic analysis is carried out to investigate the probabilistic risk of tooth flank micropitting failure using the entire SCADA datasets. A random number of datasets of smaller sizes of gear shaft torque and rotational speed are generated to substitute for the large amounts of data in the original SCADA datasets. Based on the selected random number datasets, the effect of variations in gear shaft torque and rotational speed on the probabilistic characteristics of gear tooth flank micropitting is investigated. The study shows that the HSS driven pinion gear is subject to overloading conditions, resulting in maximum contact stresses higher than the allowable contact stress of the material. Thus, the high torque value, which occurs at low rotational speed according to the data analysis, is the main cause of micropitting in WTs as it leads to high contact stress. In addition, the results of the analysis of specific lubricant film thickness show that there is a considerable risk of micropitting at the dedendum region of gear teeth under variable operational condition.
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Young, Michael A. "Effect of open fields on low building wind loads in a suburban environment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq28694.pdf.
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RIOS, MARINA POLONIA. "EFFECT OF DAMPERS ON THE DYNAMIC BEHAVIOUR OF TALL BUILDINGS UNDER WIND LOADS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25761@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROO aumento da altura dos edifícios, aliado ao surgimento de materiais mais resistentes, faz com que as estruturas sejam cada vez mais esbeltas. Com isso, a ação do vento se torna um importante fator a ser considerado nesses projetos. A sua característica dinâmica provoca efeitos de vibração nas estruturas que devem ser analisados, em especial em relação ao conforto do usuário, afetado por deslocamentos e acelerações elevadas. Este estudo aborda a utilização de amortecedores fluidos como forma de reduzir a resposta dinâmica das estruturas submetidas a cargas de vento. A carga de vento consiste em um evento aleatório, devendo ser analisada estatisticamente. Desta forma, foi adotado o Método dos Ventos Sintéticos para definir o carregamento de vento aplicado à estrutura. Os amortecedores empregados na estrutura são fluidos, altamente viscosos, portanto seu comportamento pode ser considerado linear. A avaliação do comportamento da estrutura foi realizada pelo programa computacional Robot Structural Analysis. Foi feita uma análise estática afim de realizar o pré-dimensionamento da estrutura. Em seguida, fez-se uma análise dinâmica para a estrutura submetida ao carregamento de vento, com o objetivo de se analisar a influência dos amortecedores. Foram definidos cinco modelos estruturais, com diferentes configurações de amortecedores, de forma a encontrar a sua melhor distribuição na estrutura para reduzir a resposta a níveis aceitáveis de conforto para os usuários.
With the increase in building height and the development of more resistant materials, structures are becoming more flexible. This has made the consideration of wind loads an important factor to be considered in their projects. The dynamic characteristic of these loads causes important vibration effects in these structures due to their low vibration frequencies, which must be considered in design, especially regarding the users comfort, affected by high displacements and acceleration. This study analyses the use of fluid dampers in order to reduce the dynamic response of the structure under wind loading. The wind load is a random phenomenon, and must be studied statistically. In the present work the Synthetic Wind Method has been adopted in order to generate the variation of the wind load in time. The dampers applied to the structure are fluid dampers, highly viscous, so its behavior can be considered linear. The computer software Robot Structural Analysis is used to study the structural behavior. An analysis considering the wind as an equivalent static load is adopted for the preliminary design. Then, a dynamic analysis is conducted, considering the structure under a time varying wind loading, to investigate the effect of the fluid dampers on the response. Five models are investigated, with different configurations for the dampers, in order to define the best configuration and obtain acceptable levels of displacements and acceleration.
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Galsworthy, Jon K. "Aspects of across-wind loads and effects on large reinforced concrete chimneys." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/NQ58132.pdf.
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Kathekeyan, Myuran. "Fatigue performance and design of cold-formed steel roof battens under cyclic wind uplift loads." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/122471/1/Myuran_Kathekeyan_Thesis.pdf.
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This thesis investigates the fatigue pull-through failures of steel roof batten to rafter connections and proposes suitable design equations to enhance the safety of thin steel roof battens in cyclones. Suitable design equations were developed based on both linear and nonlinear damage theories by carefully investigating the factors affecting the failure via small and full-scale experimental studies and associated numerical studies. The proposed design equations have the potential to replace the current Australian design method based on complex and time-consuming prototype cyclic tests, and also those used in many other countries.
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Wells, Eric M. "An Assessment of Surface Ice Sheet Loads and Their Effects on an Offshore Wind Turbine Structure." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1345214125.
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Moravej, Mohammadtaghi. "Investigating Scale Effects on Analytical Methods of Predicting Peak Wind Loads on Buildings." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3799.
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Large-scale testing of low-rise buildings or components of tall buildings is essential as it provides more representative information about the realistic wind effects than the typical small scale studies, but as the model size increases, relatively less large-scale turbulence in the upcoming flow can be generated. This results in a turbulence power spectrum lacking low-frequency turbulence content. This deficiency is known to have significant effects on the estimated peak wind loads.
To overcome these limitations, the method of Partial Turbulence Simulation (PTS) has been developed recently in the FIU Wall of Wind lab to analytically compensate for the effects of the missing low-frequency content of the spectrum. This method requires post-test analysis procedures and is based on the quasi-steady assumptions. The current study was an effort to enhance that technique by investigating the effect of scaling and the range of applicability of the method by considering the limitations risen from the underlying theory, and to simplify the 2DPTS (includes both in-plane components of the turbulence) by proposing a weighted average method. Investigating the effect of Reynolds number on peak aerodynamic pressures was another objective of the study.
The results from five tested building models show as the model size was increased, PTS results showed a better agreement with the available field data from TTU building. Although for the smaller models (i.e., 1:100,1:50) almost a full range of turbulence spectrum was present, the highest peaks observed at full-scale were not reproduced, which apparently was because of the Reynolds number effect. The most accurate results were obtained when the PTS was used in the case with highest Reynolds number, which was the1:6 scale model with a less than 5% blockage and a xLum/bm ratio of 0.78. Besides that, the results showed that the weighted average PTS method can be used in lieu of the 2DPTS approach. So to achieve the most accurate results, a large-scale test followed by a PTS peak estimation method deemed to be the desirable approach which also allows the xLum/bm values much smaller than the ASCE recommended numbers.
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Bennett, Jeffrey. "The Effect of Mass and Web Spacing on the Loads and Structural Response of Increasing Wind Turbine Blade Size." Thesis, KTH, Kraft- och värmeteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103434.
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The research presented considers the effect of varying shear web spacing and mass for two blades; a61.5m 5MW blade (based on the NREL5MW reference turbine) and a 100m 13.2MW blade (based onthe SNL100 blade). The variations are analyzed using HAWC2 aeroelastic simulations and Abaqus/CAE finite element simulations;and the effect of the variations is measured by comparing natural frequencies, loads, tip deflection,equivalent fatigue loads, material strength and buckling. Additionally, a tool was developed to facilitatethe modeling of blade variations. Varying the web spacing showed that the web placement is able to reduce loads, tip deflection, and equivalentfatigue loads. Mass variations demonstrated that reducing the mass will decrease edge-wise loadingand equivalent fatigue loads. The increase in blade size has shown that edge-wise fatigue loads becomelarger than the flap-wise fatigue loads for the larger blade.
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Nesterova, Mariia. "Reliability of structures exposed to traffic and environmental loads." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2056.
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Cette thèse est consacrée à l’analyse de la fiabilité du tablier du viaduc de Millau, un pont à haubans situé dans le sud de la France. Le but principal est d’extrapoler dans le temps les charges et les effets de charges sur le pont afin d’observer la fiabilité de différentes parties de la structure pendant sa durée de vie. Le viaduc de Millau est une infrastructure routière française, complexe et unique, qui est en début de vie. Il est important de pouvoir prévoir les charges extrêmes possibles sur le tablier du pont en raison de l’augmentation du volume ou du poids des véhicules. De telles prévisions nécessitent des données mesurées sur l’ouvrage, soit les charges ou actions, soit les effets de celles-ci. Les structures à grande échelle ont besoin d’une grande quantité de données, qu’il est difficile d’obtenir, de stocker et d’analyser. Cela pose un autre défi : les prévisions basées sur un temps limité et des données de surveillance accessibles. Les prévisions de charges de trafic dans ce travail sont effectuées à l’aide des données fournies par la surveillance du trafic du système BWIM pour le cas d’état limite ultime. Pour l’extrapolation de charge dans le temps, plusieurs méthodes de la théorie des valeurs extrêmes (EVT) sont comparées, une attention particulière étant accordée à l’approche POT. De plus, une contribution aux méthodes existantes pour le choix du seuil, en tant que principal défi de l’approche de POT, est apportée. Dans les grands ponts à haubans, le trafic n’est pas nécessairement l’action principale, mais les charges climatiques peuvent avoir un effet similaire ou supérieur. Le centre de ce travail est le tablier du viaduc de Millau. Par conséquent, la charge de vent statique obtenue à partir du système de surveillance de la santé structurelle du viaduc est considérée en combinaison avec les files de camions de circulation. Un modèle probabiliste est créé pour observer les probabilités de cas extrêmes pour les actions et leur combinaison. De même, l’influence de la durée de surveillance sur les intervalles de confiance pour les niveaux de retour de charges est étudiée. Dans le détail du tablier orthotrope en acier, les effets locaux causés par le passage de véhicules et les effets globaux contribuent à la valeur des contraintes. Les effets globaux proviennent des files des véhicules sur les deux voies de tablier et du vent statique dans une direction perpendiculaire. Dans cette thèse, un modèle d’éléments finis du pont est créé afin d’évaluer les contraintes dans le pont. Cela offre également la possibilité de prévoir l’état limite de fatigue. Habituellement, les dommages de fatigue accumulées dans un détail pendant la période de surveillance sont extrapolées linéairement. Le travail actuel propose une méthodologie pour extrapoler le nombre de cycles de fatigue dans le temps avec l’approche POT, qui prend en compte une variation du trafic en volume et en poids avec le temps. Une comparaison de l’approche proposée avec la méthode classique est effectuée et utilisée dans l’analyse de fiabilité en raison de fatigue. Une analyse de fiabilité est également effectuée pour l’état limite ultime afin de comparer les résultats obtenus avec plusieurs approches de EVT, d’observer l’importance des actions du vent sur la fiabilité du tablier et de comparer les prévisions basées sur EVT avec les modèles de charge de calcul des normes Européennes pour le trafic et le ventThe Thesis is dedicated to reliability analysis of the deck of Millau viaduct, a cable-stayed bridge located in Southern France. The main interest is the extrapolation in time of loads and load effects affecting the bridge in order to observe the reliability of chosen elements during the operational life of the structure. Millau viaduct is a complex unique bridge of French road infrastructure in the early stage of its life. It is important to be able to predict possible extreme loads on the deck of the bridge due to traffic growing in volume or weight. Such predictions require data from monitored actions or load effects in elements of the bridge. Large-scale structures need an enormous amount of data, that is not easy to obtain, to store and to analyze. It leads to another challenge - predictions based on limited time and accessible monitoring data.In the current work, predictions for traffic loads are done using provided data from bridge Weigh-in-Motion (BWIM) traffic monitoring for the case of the the ultimate limit state (ULS). For load extrapolation in time, several methods of Extreme Value Theory (EVT) are compared, with the most attention to the Peaks Over Threshold (POT) approach. Moreover, a contribution to existing methods for threshold choice, as the main challenge of POT approach, is made.In large cable-stayed bridges, not necessarily traffic is the leading action, but environment loads can have similar or superior effect. The focus of this work is on the deck of Millau viaduct, therefore, static wind loads obtained from structural health monitoring (SHM) of the viaduct are considered in combination with queues of traffic lorries. A probabilistic model is made to observe probabilities of extreme cases for both actions and their combination. As well, the influence of monitoring duration on confidence intervals for return levels of loads is studied.For the steel orthotropic deck of the bridge, both, local effects caused by passing vehicles and global effects, contribute to values of stresses. Global effects are coming from traffic queues on both lanes and static wind in a perpendicular direction. In this Thesis, finite element model (FEM) of the deck is performed in order to assess stresses in the deck. That brings a possibility to make predictions for the fatigue limit state too. Usually, fatigue damage accumulated in a chosen part of the deck during a monitoring period is extrapolated in time linearly. The current work proposes a methodology to extrapolate numbers of fatigue cycles in time with the POT approach, which accounts for a change in traffic in volume and weight with time. Comparison of the proposed approach with the classical method is made and used in the fatigue reliability analysis. Reliability analysis is made as well for the ULS in order to compare the results obtained from several EVT approaches, to observe the importance of wind actions on the reliability of the deck, and to compare EVT-based predictions with design load models of European Norms (EN) for traffic and wind
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Lim, keng gein. "P-delta Effects on a Steel Moment Frame Subjected to Sidesway Forces Caused by Unsymmetrical Live Load Patterns." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1622.
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Symmetrical steel moment frames that are subjected to sidesway forces due to unsymmetrical live loads will undergo sidesway. The P-delta effects on a moment frame under the influence of sidesway forces is studied. The effective length method is used for the second-order analysis specified in the American Institute Steel Construction - Load and Resistance Factor Design (AISC-LRFD). This study investigates the P-delta effects on a multi-story, multi-bay steel moment frame subjected to sidesway forces caused by various unsymmetrical live load patterns. The study focuses on the interaction of axial and bending moment in the columns. The actual response of a moment frame is estimated by amplifying the results of a first-order elastic analysis using moment magnification factors. The moment magnification factors for each story of the steel moment frame are summarized.
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Ford, Rebecca Jane. "The effect of shading and crop load on flavour and aroma compounds in Sauvignon blanc grapes and wine." Master's thesis, Lincoln University. Agriculture and Life Sciences Division, 2007. http://theses.lincoln.ac.nz/public/adt-NZLIU20080523.100013/.
Full textAbstract:
The effects of crop load and berry exposure on the composition of Marlborough Sauvignon blanc grapes and wine from the Brancott vineyard, Blenheim, were explored.
Commercially grown, 2-cane and 4-cane Sauvignon blanc vines were used with a row orientation of north-south. Two exposure treatments were imposed in the following manner: complete leaf removal was undertaken in the fruit zone and 50% shade cloth was erected to give a uniform shading treatment to half the trial vines. Weekly thirty-berry and whole bunch samples were taken from each of the 32 plots with the exception of the veraison period when two samples per week were taken. Vine vigour was assessed using pruning and leaf area per vine data. Harvest occurred on different dates for 2-cane and 4-cane pruned vines so that fruit attained from both treatments had similar °Brix. Fruit was processed at the Lincoln University winery. Must analysis and wine analysis were
undertaken. As expected, 4-cane vines had almost double the yield of 2-cane vines. Higher crop load
significantly reduced leaf area per shoot and shoot thickness. Lower leaf area to fruit ratio
for 4-cane berries resulted in delayed onset of veraison and slowed the rate of sugar accumulation. Crop load, which limited leaf area to fruit ratio, appeared to be the dominant
factor in determining timing of grape physiological ripeness as expressed by °Brix over
other factors such as fruit exposure. Malic acid, tartaric acid, IPMP (iso-propylmethoxypyrazine)
and IBMP (iso-butyl-methoxypyrazine) were lower at equivalent °Brix in 4-cane compared with 2-cane berries. Significantly higher concentrations of quercetin were found in exposed compared to shaded berries. Must analysis showed a significant influence of crop load on berry titratable acidity and pH, reflecting berry ripening results. Exposure significantly increased the concentrations of nitrogenous compounds in 4-cane must yet showed no influence on 2-cane must.
After wine processing lower malic acid concentrations in wines made from 100% exposed
fruit became evident in lower wine titratable acidity but showed no influence on wine pH.
Bentonite addition to wines had a small but statistically significant influence on wine by
reducing pH, titratable acidity and alcohol. Bound sulphur concentrations were significantly
higher in 4-cane versus 2-cane wines. At harvest, methoxypyrazine levels in grapes and wines were very low; IBMP concentrations where significantly lower than those normally found in Sauvignon blanc wines from Marlborough. This was attributed to the absence of basal leaves from the shoots of ripening berries.
The results suggest that leaf area to fruit ratio is a powerful determinant of grape and wine
quality.
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Ford, R. J. "The effect of shading and crop load on flavour and aroma compounds in Sauvignon blanc grapes and wine." Lincoln University, 2007. http://hdl.handle.net/10182/498.
Full textAbstract:
The effects of crop load and berry exposure on the composition of Marlborough Sauvignon blanc grapes and wine from the Brancott vineyard, Blenheim, were explored. Commercially grown, 2-cane and 4-cane Sauvignon blanc vines were used with a row orientation of north-south. Two exposure treatments were imposed in the following manner: complete leaf removal was undertaken in the fruit zone and 50% shade cloth was erected to give a uniform shading treatment to half the trial vines. Weekly thirty-berry and whole bunch samples were taken from each of the 32 plots with the exception of the veraison period when two samples per week were taken. Vine vigour was assessed using pruning and leaf area per vine data. Harvest occurred on different dates for 2-cane and 4-cane pruned vines so that fruit attained from both treatments had similar °Brix. Fruit was processed at the Lincoln University winery. Must analysis and wine analysis were undertaken. As expected, 4-cane vines had almost double the yield of 2-cane vines. Higher crop load significantly reduced leaf area per shoot and shoot thickness. Lower leaf area to fruit ratio for 4-cane berries resulted in delayed onset of veraison and slowed the rate of sugar accumulation. Crop load, which limited leaf area to fruit ratio, appeared to be the dominant factor in determining timing of grape physiological ripeness as expressed by °Brix over other factors such as fruit exposure. Malic acid, tartaric acid, IPMP (iso-propylmethoxypyrazine) and IBMP (iso-butyl-methoxypyrazine) were lower at equivalent °Brix in 4-cane compared with 2-cane berries. Significantly higher concentrations of quercetin were found in exposed compared to shaded berries. Must analysis showed a significant influence of crop load on berry titratable acidity and pH, reflecting berry ripening results. Exposure significantly increased the concentrations of nitrogenous compounds in 4-cane must yet showed no influence on 2-cane must. After wine processing lower malic acid concentrations in wines made from 100% exposed fruit became evident in lower wine titratable acidity but showed no influence on wine pH. Bentonite addition to wines had a small but statistically significant influence on wine by reducing pH, titratable acidity and alcohol. Bound sulphur concentrations were significantly higher in 4-cane versus 2-cane wines. At harvest, methoxypyrazine levels in grapes and wines were very low; IBMP concentrations where significantly lower than those normally found in Sauvignon blanc wines from Marlborough. This was attributed to the absence of basal leaves from the shoots of ripening berries. The results suggest that leaf area to fruit ratio is a powerful determinant of grape and wine quality.
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Alberti, Franco Augusto. "Determinação experimental em túnel de vento dos efeitos estáticos de proteção causados por edificações vizinhas : contribuição para a revisão dos fatores de vizinhança da NBR-6123." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/127909.
Full textAbstract:
Efeitos de interferência aerodinâmica por vizinhança ocorrem inevitavelmente em edificações imersas em contexto urbano. Com base nas características da vizinhança que envolve o entorno de uma edificação, estes efeitos consequentemente podem reduzir ou majorar as ações do vento sobre a mesma. Tendo em vista a complexidade do problema em estimar o real ambiente em que um edifício estará situado e sua influência no comportamento do vento, torna-se muito difícil a codificação destes efeitos em documentos normativos, específicos para cada situação de projeto. No entanto, fatores de redução e majoração das ações do vento sobre as edificações podem ser determinados de acordo com as características da vizinhança presente no ambiente em que estão inseridas. Neste trabalho são analisados quatro modelos reduzidos de edifícios altos e suas vizinhanças adjacentes. Os modelos foram testados em túnel de vento, no Laboratório de Aerodinâmica das Construções da Universidade Federal do Rio Grande do Sul, sob duas configurações de ensaios, uma com a edificação isolada e outra com a edificação na presença da vizinhança na qual estará imerso. A partir dos resultados obtidos no túnel, foram calculados coeficientes de força para cada modelo, em relação a dois eixos ortogonais com origem próxima ao centro de torção da secção transversal correspondente ao pavimento tipo. Dos quatro casos estudados, todos apresentaram variações significativas dos coeficientes de força quando na presença de edificações vizinhas. Para estes edifícios, foram calculados fatores de vizinhança respectivos aos ângulos de vento mais influentes ao dimensionamento estrutural dos mesmos. A respeito das análises, notou-se que sob vizinhança densa, houve uma grande redução das ações do vento, enquanto que brechas entre as estruturas de interferência, traduziram em aumentos das ações do vento sobre as edificações estudadas.Neighborhood interference effects due to nearby strucutres, inevitably occur on buildings immersed in urban context. Based on the characteristics of the neighborhood surrounding the vicinity of a building, these effects therefore can reduce or increase wind actions. Given the complexity of the problem in estimating the real environment where a building is located and its influence on wind behavior, it is extreme hard to encode these effects in regulation codes by specifying situations for each proposed project. However, reduction and increase factors on the wind actions over buildings can be determined according to the caracteristics of its neighborhood at the environment in which they locate. This paper analyzes four scale models of tall buildings and its surrounding structures. The models were tested in the wind tunnel at the Laboratório de Aerodinâmica das Construções of the Universidade Federal do Rio Grande do Sul, in two configurations tests, one with the building in isolated situation and the other with the building in the corresponding vicinity. The results obtained in the wind tunnel tests were used to determine strength coefficients for each model in relation to the both orthogonal axes with its origin near the torsional center of the transversal section correspondent to the standard floor of the buildings. For the four cases studied, all the test results showed significant variations at force coefficients in the presence of neighboring structures. For each case studied, interference factors were calculated due to sorrounding structures for the most influential wind angles for the structural design. Regarding the analysis it was noticed that under dense neighborhood, there was a large reduction of the wind loads, while gaps between interference structures resulted in increases of wind actions over the studied buildings.
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Merlier, Lucie. "On the interactions between urban structures and air flows : A numerical study of the effects of urban morphology on the building wind environment and the related building energy loads." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0070/document.
Full textAbstract:
Cette thèse exploratoire pose les bases scientifiques et méthodologiques d’une approche transversale visant à étudier l’énergétique urbaine et le bio-climatisme. Elle fait appel à des concepts et des outils de l’architecture et l’urbanisme, et à la physique du bâtiment et de la ville. Cette thèse étudie les relations entre la morphologie urbaine et les processus aérodynamiques qui se développent dans la canopée urbaine et leurs effets sur la demande énergétique des bâtiments induite par les infiltrations d’air et les échanges thermiques convectifs. Les spécificités de l’aérodynamique et de la physique urbaines sont d’abord synthétisées et la morphologie de tissus urbains réels est analysée. Une typologie générique de bâtiments isolés et une autre d’îlots urbains en sont déduites. Le modèle CFD est ensuite validé par comparaison des prédictions du modèle avec des résultats expérimentaux et numériques, et des expérimentations numériques sont réalisées sur les différents types morphologiques. Les écoulements moyens sont analysés dans leurs rapports avec la morphologie bâtie, et la distribution des coefficients de pression sur les façades des bâtiments est analysée. Ensuite, les échanges thermiques sont couplés aux processus aérodynamiques. L’amélioration des estimations des échanges convectifs des bâtiments grâce à la CFD est vérifiée par comparaison des résultats de simulation avec des données expérimentales et numériques, ainsi qu’avec les valeurs standard. Une adaptation des fonctions de paroi relatives au transfert thermique est proposée sur la base d’études existantes, et la distribution des échanges convectifs sur les façades de bâtiments est analysée. Enfin, la demande énergétique des bâtiments due aux infiltrations d’air et à la transmission de chaleur au travers de leur envelope est estimée pour différents types morphologiques, et comparée avec les valeurs estimées suivant une approche réglementaire. Les résultats de cette thèse mettent en évidence les effets des propriétés topologiques et métriques des bâtiments et ensembles bâtis sur le développement de recirculations d’air dans la canopée urbaine. Celles-ci induisent une distribution et intensité hétérogènes des coefficients de pression et d’échange convectif sur les façades des bâtiments, qui influent sur le comportement thermique des bâtiments non isolés et perméables à l’air. Par ailleurs, l’estimation de leur demande énergétique diffère suivant si celle-ci est basée sur les valeurs simulées ou standard des coefficients de pression et d’échange convectif. Cependant, l’influence relative de la structure bâtie sur la demande énergétique des bâtiments apparaît plus importante pour les bâtiments isolés thermiquement. La différence entre la demande énergétique par unité de surface de plancher, due aux infiltrations d’air et pertes thermiques au travers de l’enveloppe peut varier de 18% à 47% suivant si le bâtiment est isolé ou situé dans un environnement bâtiThis thesis is an exploratory study that lays the scientific and methodological foundations of a transverse approach for studying urban energy and bio-climatic issues. This approach involves concepts and tools of building and urban physics as well as urban planning and architecture. It addresses the relations between urban morphology and aerodynamic processes, and studies their effects on the building energy loads due to infiltration and convective heat losses. This thesis is divided into three main parts. The first part synthesizes the specificities of urban aerodynamics and urban physics, and analyzes existing urban fabrics from a morphological point of view. Generic typologies of isolated buildings and urban blocks for small scale aerodynamic studies are deduced. The second part validates the computational fluid dynamics (CFD) model (steady RANS RSM) against detailed experimental and numerical data, and presents the numerical experiments performed on the different morphological types. Mean flow structures that develop according to the construction shape and built environment, as well as pressure distribution on the building outer walls are examined. The last part couples heat and air fluxes to evaluate the contribution of urban air flows on the building energy loads. The improvement brought by CFD to the assessment of building convective heat transfers is verified by comparing numerical results to experimental data, detailed numerical studies and standard correlations. An enhanced temperature wall-function adapted for forced convection problems is adjusted to the model based on existing studies, and the convective heat transfers distribution on building facades is analyzed. Finally, the building energy loads due to air infiltration and heat transmission are estimated for typical constructions and compared to standard values. The results of this thesis show strong effects of the topology and dimensionality of constructions and urban structures on the development of recirculation phenomena within the urban canopy layer. The related aerodynamic conditions yield heterogeneous pressure and convective heat transfer intensities and distributions on building facades, which depend upon the considered built morphology. Their effects on building energy loads are logically particularly important in absolute value for buildings that are neither insulated nor air tight. Nonetheless, the estimates of the building energy needs based on standard or simulated pressure and convective heat transfer coefficients often show substantial deviation. Focusing on the relative contribution of the built structure, the effects of the aerodynamic context appear more influential for insulated buildings. Essentially, switching from an exposed to a sheltered building may decrease the energy needs per surface unit of floor due to air infiltration and heat transmission through outer walls by 18% up to 47% according to simulation
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Kaabia, Bassem. "Méthodes avancées d'évaluation des charges de vent sur les structures de concentrateurs solaires." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11315.
Full textAbstract:
L’énergie solaire photovoltaïque concentré (CPV) est une solution de remplacement prometteuse aux structures solaires conventionnelles. Ce type de structure modulable doit être optimisé afin d’être compétitif par rapport aux autres types de production d’énergie. Les forces de vent demeurent la première préoccupation dans la conception de la structure porteuse en acier d’un tel système. L’objectif principal de cette recherche est d’assembler des outils numériques et analytiques afin de prédire les caractéristiques de sa réponse dynamique sous charges de vent turbulent. La maîtrise de cette étape est essentielle afin d’étudier d’une façon plus générique des solutions d’optimisation de la structure support par rapport à sa réponse dynamique sous charges de vent. Pour ce faire, la méthodologie principale de cette étude est composée en trois parties : (i) étude expérimentale à grandeur nature de la réponse globale sous les conditions réelles du vent ; (ii) développement des modèles d’analyse numérique dans lesquels les caractéristiques de structures réelles et des
modèles de forces aérodynamiques adéquates sont prises en compte ; (iii) application des outils développés dans une étude paramétrique pour évaluer plusieurs solutions à partir de cas d’étude dans le contexte d’une conception préliminaire.
Cette thèse est présentée sous forme de deux articles qui ont été soumis dans des revues évaluées par des comités de lecture ainsi que d’un article soumis et présenté dans un congrès international qui démontrent les contributions de cette recherche pour améliorer les pratiques de calcul des charges de vent sur des structures de concentration solaire non conventionnelles. Ces articles sont présentés comme suit (a) Étude expérimentale à échelle réelle de la réponse d’un prototype de concentrateur solaire sous charges de vent. Ce premier article a permis la validation de calcul des coefficients de forces aérodynamiques statiques et la révision des hypothèses de l’application du code ASCE 7-10 pour prédire les forces maximales agissant sur la structure dans la direction du vent ; (b) l’analyse temporelle
de la réponse dynamique d’une structure de concentrateur solaire sous charges de
vent. Cette étude a montré que le modèle et la méthode d’analyse développés selon des hypothèses simplifiées permettaient de prédire correctement les caractéristiques statistiques de la réponse dynamique mesurée en cohérence avec la méthode spectrale stochastique ; (c) Étude des effets des configurations structurales et des paramètres de vent sur l’optimisation de structure solaires sous charges de vent. Cette étude paramétrique a mis en évidence l’importance de l’effet des paramètres structuraux et ceux définissant le vent sur l’optimisation de la conception structural pour ce type de structure. Des recommandations pour optimiser l’action dynamique dans une phase de conception préliminaire ont été proposées. Ce projet de recherche a démontré finalement l’importance d’étudier d’une façon juste et pratique la réponse dynamique sous charges de vent qui mène à résoudre des préoccupations d’optimisation liées à différents types de structures d’énergie solaire en adoptant des hypothèses pratiques pour les ingénieurs.Abstract : Concentrated Solar Photovoltaic (CPV) is a promising alternative to conventional solar structures. These solar traking structures need to be optimized to be competitive against other types of energy production. Wind action is the main concern in the design of the steel support structure of such movable system. The main purpose of this research is to assemble advanced numerical and analytical tools that allows realistic dynamic study of structures under wind loading. This help to study accurately optimized alternative in term of selecting structural and wind site conditions parameters. The methodology of the present study involves three main steps : (i) experimental full-scale study of the global response under real life wind conditions ; (ii) numerical modeling that captures the characteristics of the real structures and include the aerodynamic force models to conduct time-domain dynamic analyses ; (iii) preliminary design application that include the study of the effect of stuctural and wind parameters in optimizing the dynamic wind action and consequently the steel support structure. The thesis is presented as an ensemble of three articles written for refereed journals and a conference that showcase the contributions of the present study to thoroughly understand the wind load effect on these nonconventionnel structures. The articles presented are as follow (a) full-scale measurement of the response of a CPV tracker structure prototype under wind load. The results presented in this first article help design engineers to evaluate the use of the aerodynamic force coefficients for calculating wind load on similar structures and to apply properly the ASCE7-10 in evaluating the maximum design wind force using the equivalent static approach ; (b) time-domain analysis of solar concentrator structure under gust wind. This study showed that the developed time-domain model using simplified hypothesis could successfully predict the statistical parameters of the measured dynamic response in coherence with the stochastic spectral approach ; (c) effect of structure configurations and wind characteristics on the design of solar concentrator support structure under dynamic wind action. This parametric study highlighted the importance of selecting structural and wind parameters in order to minimize the dynamic action and the steel support structure. Recommendations for optimizing dynamic wind action in a preliminary design phase were proposed. The present research project has shown the need to study accurately wind response to solve optimization concerns related to different type of solar system structures. In addition, this study proposes simplified methods that are useful for practical engineers when there is the need to solve similar problems.
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Aflatooni, Mehran. "Synthetic rating system for railway bridge management." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/81784/1/Mehran_Aflatooni_Thesis.pdf.
Full textAbstract:
This thesis developed a condition assessment and rating method to identify those bridges in a network which are in most need of repair for an effective life cycle management. The method estimates the contribution of critical factors towards bridge deterioration and uses structural analysis to overcome the subjectivity of traditional current condition assessment methods. This research was a part of the CRC project titled 'Life Cycle Management of Railway Bridges'. Efficient usage of resources and enhancing the safety and serviceability of railway bridges are the significant outcomes of using the proposed method.
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NEMADE, MAYUR MADHUKAR. "EFFECT OF VARIOUS DESIGN PARAMETERS OF CHIMNEY UNDER WIND LOAD." Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/20006.
Full textAbstract:
This thesis investigates the impact of wind on high-rise chimneys, focusing on predicting
wind loads and analysing the effects of varying chimney dimensions. Using
computational fluid dynamics (CFD) simulations, the study considers variables such as
wind speed, direction, turbulence, chimney shape, size, and parameter variations.
Simulations were conducted using ANSYS CFX 2022 R2 and AutoCAD, covering wind
incidence angles from 0 to 180 degrees. Pressure contours and coefficient of pressure
(Cp) values were analysed to understand pressure distribution and wind-induced forces.
Results showed that pressure values varied with wind angle, predominantly exhibiting
suction forces. Cp values were consistently negative, indicating the presence of suction
forces.
The findings highlight the influence of wind angle on chimney pressures, with a decrease
in suction forces as the wind deviates from perpendicular. Wind velocity affects pressure
variations, with higher velocities leading to intensified positive and negative pressures.
Different wind zones result in varying pressure distributions, from laminar flow in low velocity regions to turbulent flow in higher wind zones.
The study also explores the impact of chimney dimensions. Larger top diameters promote
smoother flow transitions, reduced pressure drop, and improved flow efficiency. Smaller
top diameters may cause increased turbulence and pressure fluctuations. Base diameter
variations affect flow separation, windward flow deflection, and wind pressure
distribution. Chimney height influences flow dynamics, with taller chimneys exhibiting
more pronounced upward airflow. Chimney wall thickness affects streamlines' coherence,
with thicker walls promoting laminar flow and thinner walls causing turbulence.
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VIPLAV, VIKRANT. "COMPARATIVE RESPONSE ANALYSIS OF BUILDINGS WITH AND WITHOUT BRACING UNDER WIND LOAD EFFECT." Thesis, 2019. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16811.
Full textAbstract:
In the present era, the trend in construction industries is more inclined towards tall building i.e. vertical expansion of the building, due to the scarcity of land available and increasing population. The cost of the building increases as the height of the building increases due to the increase in the weight of the building and forces. As the height of the building increases, lateral movement of the building also increases (sway).To reduce the sway one of the techniques used is ‘bracing’. There are many types of bracings normally used in the practice such as x-bracing, v-bracing, inverted v-bracing, eccentric bracing, k-bracing etc. Also these bracing can be provided at different positions in the buildings. In the present study, 20 storey steel structure of height 60m (3 m each storey) was considered. The structure was designed as per IS 800:2007 code with dead load, live load and wind load combinations. Static analysis was performed using E-tabs software assuming, importance factor as 1.15, Terrain category IV and Topography to be flat. The analysis was performed according to IS 875:2015. The analysis was performed for buildings of two plan shapes, square and plus shape, with x-bracing, v-bracing, inverted vbracing, diagonal bracing, k-bracing and without bracing. The results were compared and studied. It was found that the lateral response of the structure was more in the structure without bracing than other models. It was also observed that lateral loads were more in the case of Xbracing. Finally, it can be concluded that Inverted V-bracing is better for wind loading.
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NAGAR, SURESH KUMAR. "EFFECT OF UNCONVENTIONAL SHAPES ON RESPONSE OF TALL BUILDINGS UNDER WIND LOAD." Thesis, 2022. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18978.
Full textAbstract:
With the advances in construction methods, materials, and technologies, more high rise buildings with unconventional shapes have been continuously built. A large number
of tall buildings with irregular shapes have been built in past years in urban areas due to a
shortage of land and demand for good architectural design. As the wind velocity increase
with height, the top of the building may experience a higher wind. Tall buildings are the
structures that are more sensitive to wind loads, and thus the response to the wind load is
the main concern of designers while designing tall buildings. Most of the tall buildings are
bluff bodies. As flow separates and reattaches around bluff bodies, the external shape of
tall buildings plays an influential role in the generation of wind load on high-rise buildings.
High-rise residential buildings are commonly built as twin towers. Twin tall buildings
are subjected to the proximity effects due to small gaps between them. Under the influence
of proximity, the wind load on tall buildings may differ from that on the isolated buildings.
The codes and standards related to the wind loads are generally do not consider these
proximity effects. Further, no analytical formula is available to evaluate the wind effect on
irregular shape tall buildings and proximity effects between twin towers, which
necessitates more experimental or analytical study for irregular shape tall buildings.
In the present study, four different plan shapes, namely square, plus-1, plus-2, and H plan, are considered. The floor area and height of all four models are kept the same. The
plus-1 and plus-2 plan shapes are prepared by providing the large-sized recessed corners
in the rectangular plans of different sizes, whereas the H-plan shape is prepared by
providing recessed cavities on the two opposite faces of a rectangular plan shape. The study
has been conducted in three phases, namely (i) pressure measurements through wind tunnel
study in isolated and interference conditions, (ii) force evaluation through pressure
integration technique, and (iii) study of the response of prototype buildings to wind loads
calculated on scaled models.
In the first phase, to investigate the wind-induced pressure at the surfaces of the building,
four rigid models scaled at 1:300 as described earlier are tested in an open circuit layer
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wind tunnel having a working section of 2 m x 2 m cross-section and 15m length. The wind
flow characteristics inside the tunnel are simulated similar to the Indian sub-urban terrain
with well-scattered objects with a height between 1.5 to 10 m according to the Indian
standard IS 875 (part 3): 2015. The mean wind speed and turbulence intensity profile with
a power-law index of 0.22 is simulated in the tunnel. The turbulence intensity near the floor
of the wind tunnel and wind velocity at building height is 12% and 9.87 m/sec,
respectively. The pressure models are prepared with a 4 mm thick transparent Perspex sheet
with stiff faces to ensure sufficient rigidity and strength of the model. The pressure
measurement study is conducted in two parts. In the first part, the pressure models are
tested in isolated conditions for wind directions of 0, 300
, 600
, and 900 angles at an interval
of 300
to assess the effects of wind direction on the surface wind pressure. In the second
part, the pressure models are tested with an interfering building model present upstream of
the pressure model at different locations. The interfering building models are made of
wooden material with dimensions similar to the pressure models. Interference effects are
assessed for three different positions of interfering building, such as full blockage, half
blockage, and no blockage. From the time history of fluctuating pressure data, the mean,
maximum, minimum and r.m.s pressure coefficients are evaluated at each pressure point
on the surface of the model in isolated and interference conditions.
In the second phase of the study, local wind force coefficients at various levels of the
models and the overall base forces have been evaluated through the pressure integration
technique. The local forces at each level of the model are calculated by integrating the local
forces of each pressure tap at that particular level. The overall base forces and moments
are calculated by integrating the force and moment of all levels. The forces in along-wind
and across wind directions are presented as mean and r.m.s coefficients.
In the third phase of the study, the responses of prototype buildings of the four models
to the wind load calculated through wind tunnel study on the scaled models are studied
through analytical study. The effects of various wind directions and various interference
conditions have been assessed on the response of four buildings through stress parameters,
including axial forces, the moment in X and Y directions, and twisting moments. At last,
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the effects of the various plan shapes on the response of tall buildings under wind loads
have been investigated.
The results show that wind flow direction has significant effects on the pressure
distribution on the surfaces of the models. For the square model, the wind directions normal
to the surfaces are critical direction. The wind direction of 600
generates the most critical
positive and negative mean pressure on the plus-1 model. The effects of wind direction on
the pressure on the plus-2 model are not as much severe as the plus-1 model. Pressure
distribution on the front faces of all models is completely different in interference
conditions from those in isolated conditions. The influence of interference on the square
and H-plan model are beneficial, while it has negative effects on some face of the plus-1
model. The along-wind mean local wind forces at normal wind incidence are higher than
those at oblique wind incidence. The along-wind forces in all interference conditions
decreased significantly from those in isolated condition. The values of along-wind forces:
drag and moment at normal wind incidence of 00
and 900
angles are larger than those at
oblique wind incidence in isolated condition. The CFD and CMD values are likely to be
reduced significantly in interference conditions. The effects of change in cross-sectional
shape are significant on the across-wind forces. The effects of cross-sectional shape are
dominant for wind flow at oblique angles in isolated condition while more at half blockage
condition of interference. The axial force is independent of the building cross-section. All
the buildings have the same axial force in central columns. The maximum twisting moment
is observed in PL-2 Building in isolated as well as in interference conditions. The H building show the best performance in isolated condition.
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Liu, Chung-Tai, and 劉中泰. "The Effect of High-Rise Building Cross-Section On The Design Wind Load." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/59268497804651857986.
Full textAbstract:
碩士淡江大學
土木工程學系
89
Title of Thesis： Total pages：156 The Effect of High-Rise Building Cross-Section On The Design Wind Load Name of Institute：Graduate Institute of Civil Engineering , Tamkang University Graduate Date： July, 2001 Degree Conferred：Master of Science Name of Student：Chung-Tai Liu Advisor：Dr. Chii-Ming Cheng 劉 中 泰 鄭 啟 明 博士 Abstract： In a modern city where land is expansive, high-rise building plays a important role in city development. For high-rise buildings, wind force is an important lateral design load besides earthquake force. At present, design wind load is treated as a static force in the official building code. It can’t describe the random nature of the wind force. So, high-rise buildings’ wind tunnel experiment is a better procedure to estimate the wind load. For pleasing to the eye, building tends to have various shapes. Therefore, it becomes important to apprehend the effect of building cross-section on the design wind load. This paper is to measure the wind forces acting on the four different series of building cross-section in both urban flow and city flow field. The four series of cross-section are (1)pure polygon cross-section, (2)rectangular with different width/depth ratio, (3)different form of L cross-section, (4) irregular cross-section. The volume, cross-section area and height of all models are identical to a square prism with aspect ratio of 7. Based on the selection procedure developed by the wind tunnel laboratory of Colorado State University, several critical load cases were selected for the design purpose. After analyzing, the design wind load at each floor of the target building can be calculated. The experimental results indicate that, if peak load is greater that can cause greater design wind load. Most models have greater design wind load in city flow field. Pure polygon cross-section model has less wind force. And circular shape can decrease design wind load effectively. Comparing the experiment of the rectangular shape models, increasing the width/depth ration can decrease lateral design wind load but raise torsional design wind load. In different form of L cross-section series, these models have unsymmetrical cross-section. Hence, they have greater torsional design wind load than the symmetrical cross-section models. Irregular cross-section also has high design wind load. Key word：high-rise building, wind tunnel experiment, force balance, cross-section, design wind load
28
Shieh, Yeu-Lih, and 謝雨利. "The Effect of Geometric Shape on The Design Wind Load of High-rise Buildings." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/61184060260540425896.
Full textAbstract:
碩士淡江大學
土木工程學系
88
For tall and slender structures such as high-rise buildings and long span bridges, wind force is an important lateral design loading besides earthquake force. At present, design wind load is treated as a quasi force, which is primarily based upon alongwind force in the official building code. It can't describe the complex nature of the wind force and its effects on buildings. So, high-rise buildings' wind tunnel experiment is a better procedure on studying the wind load. It becomes more important today that the effect of geometric shape on high-rise buildings' wind load. Because of high-rise buildings' volume and height to the surrounding architectures, we will have more challenge on the design of structures' appearance. This paper is to measure the wind forces acting on the models of four different geometric shapes, in both urban flow field and city flow field. The four geometric shapes are square shape models with (1)different height-to-width ratio, (2)different chamfered corner ratio (3)different height to beginning shrinkage ratio, (4)different shrinkage width at each level. The volumes of all prisms are the same as the one with height-to-width ratio of 5. Force balance technique was used to measure the wind force. Combining with the techniques of random vibration analysis, the design wind load at each floor of the target building can be calculated. Based on the selection procedure developed by the wind tunnel laboratory of Colorado State University, several critical load cases were selected for the design purpose. The experimental results indicate that, high-rise building with higher height-to-width ratio, will increase the lateral and torsional wind load. Chamfering the corner of square cross section of the prism will mainly decrease the torsion force of models. The same effect is showed in the rms acrosswind response. Comparing the experiments of the models with different starting shrinkage ratio, model with lower starting shrinkage ratio will have greater base moment. According to the experiments of the models with different each level's shrinkage width, in both x and y directions, more shrinkage on each level will decrease the wind load.
29
Chen, Cheng-Hao, and 陳政豪. "Applications oF Neural Network on the Predictions of Interference Effect on Design Wind Load of Different Geometry Building." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35837009457215739083.
Full textAbstract:
碩士淡江大學
土木工程學系碩士班
97
Tall building plays an important role in the city development due to the limited land, and the interference effects from the adjacent buildings cannot be ignored. Due to the complexity of the interference phenomenon, the building interference phenomenon is too complicated a problem for traditional engineering approaches. A more sensible way to deal with this problem would be using good quality aerodynamic database with IT techniques such as neural network. The aim of this thesis is to construct an aerodynamic database on building interference that can be used together with the wind code or/and single building’s aerodynamic database for wind resistant design of tall buildings. Through the comparison of the weighted interference index, the results of wind tunnel experiments indicate, that the interference effects increase with buildings aspect ratio. In this study the Artificial Neural Network technique was applied on an existing limited aerodynamic database to predict tall buildings’ interference factor (IF), and use the result to calculate design wind load. The ANN model is radial basis function (RBF) neural network, and the framework includes input layer, a single hidden layer and output layer. By centers and radial basis function in the hidden layer to create a neural network. The results indicate that, in the training phase, the error almost can smaller than 3%, in the predicting phase, except acrosswind background part in terrain C ,the static part and background part in all terrain are less than 7%. The resonant part in terrain A&B are within 7% to 12%. However, in terrain C the error of resonant part can be as large as 15% to 22%. In other words the resonant part need to be further improved.
30
KHATRI, ANIRUDH. "NUMERICAL SIMULATION OF WIND LOAD EFFECTS ON LOW RISE BUILDINGS." Thesis, 2022. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19401.
Full textAbstract:
Wind load plays a governing role in the designing of the roof in the coastal and hilly
regions. The shape and angle of roof slope are key parameters while designing the
structure for such loads. The present study demonstrates the variation of pressure due
to wind loads on the pitched roof of a low rising building with different roof angles.
The main parameters determining the pressure distribution over the building due to
wind loads are length, height, span and roof angle.
Most research work have already been performed for the wind load calculations for
different type of roofs in respect to different standards and conditions only for standard
building shapes. However, this study solely focuses on pitched type roof with complete
opening. The interference effect on low-rise structures is not given proper attention
despite different
The study constitutes of interference effect of different structures due to corresponding
building’s location in a controlled system performed in ANSYS CFD simulations.
Many studies on roofed structures have been performed in the past. However,
interference effect with respect to different roof angles for different rotational
arrangements of the structure were not observed in these studies. A k–ε model is used
for the pressure distribution on the roof of the building model.
The simulation was performed in ANSYS CFD with different roof slopes (α) i.e,
10°,20°,30° and for different angles of rotations(Ө) i.e, 0°,30°,45°,60°,90° and for
different spacing between the adjacent structures being different ratios of width of the
building (B) i.e, 0B, B/2, 3B/2, 2B. Pressure Coefficient (Cp) have been calculated and
different contour profiles are represented as results on the roof surfaces.
31
Jafari, Azadeh. "Effects of Turbulence on Heliostat Wind Loads." Thesis, 2020. https://hdl.handle.net/2440/135328.
Full textAbstract:
Concentrated solar thermal systems are being increasingly deployed for industrial process heating and large-scale electricity production. A major constituent of a concentrating solar plant is the field of heliostat mirrors, which reflect the sunlight onto a receiver. Heliostats are subjected to fluctuating wind loads arising from atmospheric wind. These forces are important for design of heliostats, which must survive maximum wind loads under extreme conditions. Furthermore, dynamic wind loads which lead to vibrations of the mirror panel can affect the tracking accuracy of a heliostat field. Therefore, knowledge of wind loads is necessary for design and development of a heliostat field. The main source of unsteady loads on heliostats is the fluctuating wind velocity, which results from the turbulence within the atmospheric boundary layer. Furthermore, heliostats during their operation create a blockage in the flow and unstable vortex structures in their wake. The interaction between the wakes of several heliostats in a field with each other and with the incoming atmospheric boundary layer flow affects turbulence and consequently wind loads in a heliostat field.
The research presented in this thesis focuses on the development of an in-depth understanding of the effects of turbulence within the atmospheric boundary layer on the wind loads on heliostats. Extensive wind tunnel experiments have been conducted to simulate the atmospheric boundary layer turbulence and establish its effect on unsteady wind loads. Similarities and differences of the turbulence properties with respect to the atmospheric boundary layer are discussed and the requirements for achieving similarity in measurement of wind loads in a wind tunnel are established. A correlation is developed between the intensity and integral length scale of the turbulence and the peak lift and drag forces on a heliostat at stow and vertical positions, which is employed to predict the wind loads on full-scale heliostats in a range of terrains where the turbulence characteristics of the flow vary.
In order to develop an understanding of wind loads in a heliostat field, turbulence in the wake of a heliostat in the atmospheric boundary layer is characterised. Based on the findings, variations of flow and turbulence properties in a heliostat field are discussed. Moreover, through analysis of wind loads on a second tandem heliostat placed in the wake of an upstream one, it is demonstrated that wind loads on the second heliostat are correlated with the turbulence properties in the wake. It is concluded that wind loads on a heliostat within a field can be predicted from the approaching wake flow properties. Estimations for variations of wind loads in different regions of a field are thereby made based on the findings.
After demonstrating the strong relationship between turbulence and wind loads, the effect of perimeter fences around a heliostat field on the turbulence within the atmospheric boundary layer is investigated. It is demonstrated that the intensity and integral length scale of the turbulence reduce downstream of wire mesh fences. It is found that the reduction in turbulence properties behind a wire mesh fence is mainly correlated with the mesh porosity. Based on the variations of turbulence properties behind a wire mesh fence, the feasibility of reducing the wind loads on heliostats with application of the fences is analysed.
The research presented in this thesis provides an improved understanding of the effect of turbulence within the atmospheric boundary layer on the unsteady wind loads on heliostats. The findings of this research can be used to determine the design wind loads based on the turbulence characteristics specific to a given terrain. Recommendations for improvement of heliostat design and reduction of wind loads on heliostats are made based on the results, and potentials for reducing the cost of heliostats through reduction of structural costs related to the wind loads are identified. For instance, it is demonstrated that the peak wind loads on a stowed heliostat can be reduced by 80% by decreasing the height of the heliostat panel at stow. Furthermore, it is shown that there is a potential to reduce the peak drag force on an operating heliostat and the peak lift force on a stowed heliostat by application of wire mesh fences by 48% and 53%, respectively. Moreover, the presented study provides an insight into variations of wind loads within a heliostat field which are necessary to be considered in the design of heliostats. For example, up to 80% increase in the unsteady drag force coefficient on a vertical heliostat and up to 70% increase in the peak hinge moment coefficient on an operating heliostat are predicted for high-density regions of a field. Hence, the findings highlight the need to develop the arrangement of heliostats in a field such that the dynamic wind loads on the in-field heliostats can be reduced. The results of this research provide an opportunity for production of cheaper heliostats by reducing the design wind loads.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2020
32
Yam, Jing-Wei, and 顏靖偉. "Combination of Scalar Wind Load Effects for Square Section Buildings." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/52623477038504828032.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
102
A building suffers along-wind load, across-wind load and torsional wind load simultaneously. However, their maximum values usually do not occur at the same time. In this study, wind load spectra and cross spectra are computed based on the wind pressures on building surfaces from wind tunnel tests and computational fluid dynamics (CFD) analyses. Scalar wind load effects are combined by Complete Quadratic Combination (CQC) method and AIJ(2004) method. The correlations among along-wind, cross-wind and torsional responses are considered. The respective correlation coefficient depends on the normalized wind spectra/cross spectra, the fundamental natural frequency and damping ratio. It is especially sensitive to the wind spectra. Finally, the results of AIJ (2004) method and those by CQC method are compared.
33
Liu, Shang-Hao, and 劉尚豪. "Study on Vectorial Wind Load Effects for Rectangular Section Buildings." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/20150513751659440771.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
103
Buildings under wind loads result in along-wind, across-wind and torsional wind load effects; vectorial wind load effects are their nonlinear combinations. This study concerns the building top floor corner maximum acceleration and derives new formula considering the correlation between the wind load effects. First, wind load spectra are obtained by numerical simulations, and the results are compared with those from wind tunnel tests. The correlation coefficients between accelerations depend on the normalized wind load spectra, the fundamental natural frequencies and damping ratios. In this study, two formula have been derived; the difference is that formula 1 adopts an octagonal approximation while formula 2 adopts a CQC rule. Finally, the results of the above two formula are compared with those from design code. It is found that formula 2 provides the most accurate results; the results based on design code are slightly conservative; formula 1 generally yields the most conservative results.
34
Lin, Chun-Kai, and 林群凱. "Aerodynamic Damping Effects on Structural Responses under Wind Loads." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/57180826760865084965.
Full textAbstract:
碩士淡江大學
土木工程研究所
82
The interaction between vibration of high-rise buildings and wind will result in aerodynamic damping phenomenon. This phenom- enon changes the total damping of buildings and amplitudes of vibration. In order to study this particular behaviors, aeroela- stic model experiment of square section cylinders were conducted to simulate the behaviors of high- rise buildings under the action of wind. Mass , damping and aspect ratio were chosen as the experimental parameters. The experimental results show peak value on across-wind resp- onse in open terrain flow field(BL1),but not in urban flow field (BL2). Due to a small aliment variation, about 0.3 , between the model axises and flow field axises , Certain characteristics of across-wind response can be found in the along-wind responses in open terrain flow field, but no in urban flow field . The along- wind responses of urban flow field are larger then those in open terrain flow field . In both two types of flow field , the tip displacements, decay as the danping ratio increasing. The struc- tural responses show resonant when wind speed is equal to the critical wind speed for large aspect ratio. The aerodynamic dam- ping is positive when the reduced wind speed is under 8,negative when the reduced wind speed is beyond 8 . The larger negative aerodynamic damping occur in open terrain flow field. The across wind response prediction including aerodynamic damping agrees better withmeasurement than those based only on structural damp- ing.
35
Chen, Hsien-Fu, and 陳信甫. "The effects of Turbulent Boundary Layer on high-rise building’s design wind load." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/98914086204457156999.
Full textAbstract:
碩士淡江大學
土木工程學系
91
High-rise building plays a important role in development city under the finite land. Wind force is an important lateral design load other than earthquake force for high-rise buildings. At present, building code tends to adopt quasi-static approach, and can not represent the complex random nature of wind load. So, high-rise buildings’ wind tunnel experiment is a better method to estimate the wind load. This paper is to study the effect fo flow field on design wind load. Four types of turbulent boundary layers were generated in wind tunnel to represent flow fields developed over different terrains, namely, coastal area, open land, suburban area and large city. Two goupes of building models were tested in these flow fields: (1) sqaure shaped model with different aspect ratio, (2) different geometric cross-section. Force balance technique was used to aquire the wind loads and then the design wind load at each floor were calculate through dynamic anaylsis. Based on the wind tunnel measurements, empirical models to consider the influence of terrain on design wind load were derived. The experimental results indicate that, coastal terrain has higher mean wind velocity and city has greater turbulent intensity. Most models have less design wind load in city flow field. The predicted design wind load based on the empirical model agrees reasonably with the experimental data.
36
Chung, Shen Wen, and 鍾勝文. "Aerodynamic Damping Effects of A Elastic Wall under Wind Loads." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/09291627580431771028.
Full text
37
Lin, Zheng Xun, and 林政勳. "Effects of Frequency Ratio on Building Behavior and Wind Loads." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/15524530784220182417.
Full textAbstract:
碩士淡江大學
土木工程學系
90
In recent years, high-rise building becomes a common trend in city development. Due to the slender nature of high-rise buildings, the structural natural frequency is more likely to coincide with vortex shedding frequency and result in vortex induced resonance. The excessive building vibration will introduce extra aeroelastic force in the form of aerodynamic stiffness and aerodynamic damping. Quite a few research works were conducted on either wind load characteristics of stationary pressure models or aeroelastic features of vibrating models. Limited works were done on the wind load characteristics of controlled vibrating models. In this research project, a rigid pressure model mounted on a tri-axial mode, aeroelastic base system was used to investigate the wind load of an aeroelastically simulated building model under wind induced vibration. The frequency ratio of the torsional-to-lateral mode was selected as an experimental parameter. The models’ wind pressure, response and wind velocity near wake were measured simultaneously. Therefore, besides the structural response, wind load and wake velocity, the cross-analysis can be performed to extract more information on how the motion affecting wind load characteristics of the building. The experimental results indicate that, the mean alongwind response, the R.M.S. acrosswind and torsional response increase as the wind speed grows. The oscillating model tends to exhibit lower wind load coefficients than the stationary model at wind speed other than the vicinity critical range. In the case of structural frequency ratio greater than 1.0, the acrosswind response decreases as the frequency ratio is decreasing toward 1.0. However, once the frequency ratio becoming less than 1.0, the responses of all three axes increase significantly as the frequency ratio decreases further away from 1.0.
38
GAUR, NIKHIL. "RESPONCE VINDICATION OF EFFECTS OF CORNER CONFIGURATION AND INTERFERENCE ON TALL BUILDINGS UNDER WIND LOADS USING CFD MODELLING." Thesis, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18365.
Full textAbstract:
This study explores a recent application of the computational fluid
dynamics technique “CFD” for wind analysis and its comparisons with the
conventional wind tunnel experimentations. This study is centered on the wind
response of square and corner cut-shaped building models and its optimization
caused by the variation of the wind incidence angle. Extensive rigid model
experiments of two building models of length scale 1:100 have been performed in the
boundary layer wind tunnel. The numerical analysis has been carried out with the
standard k-ε turbulence model to evaluate the force coefficients, base moments,
power spectra, external surface pressure coefficients, and flow field characteristics of
the models with variable wind angles of incidence. The comparisons between
experimental results and CFD analysis suggest the computational approach’s
viability in wind analysis of tall structures efficiently and accurately. A case study of
aerodynamic mitigation by corner cut suggests minor modification techniques
performance, efficiency, and limitations. Wind induced interference plays a vital role
in the design of tall structures. However, the complex features of structure design and
shape require a detailed wind tunnel/CFD (Computational Fluid Dynamics) study as
codal provisions don’t suffice for such scattered parameters. iv
The current study focuses on the effects of height ratio, orientation, and
blockage configuration of interfering structure on interference effects. Interference
factor (IF), transient pressure, and force spectra are used to account for the
interference effects at major probe points to understand the dynamic wind response.
To study these effects among complex arrangements, a numerical simulation for a
CFD analysis on a corner configured principal building model and a single upstream
interfering building model having identical geometry has been performed. The
configuration included six kinds of heights ratio (Hr=Hprincipal/Hinterfering).
Furthermore, force coefficients, base moments, and external surface pressure
coefficients both in the along and across wind direction are determined and listed for
wind incidence angle of attack of 0° to 90° at an interval of 15°. Interference effects
among full, half, and no blockage conditions were investigated. The data is presented
in terms of the interference factor relating wind load responses of the isolated
principal building to interference configuration. The results indicate that in close
proximity of structure, the shielding effect suppresses the interference effects on the
principal building, but across wind responses have been investigated in close vicinity
configurations too. This study also suggests the interfering model’s orientation
contributes to great measures to the wind response under interference.
39
Chen, Pei-Chun, and 陳姵君. "Application of neural network on the predications of interference effects on buildings design wind load." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/95281716597060215909.
Full textAbstract:
碩士淡江大學
土木工程學系碩士班
95
High-rise building is sensitive to wind. In Taiwan, typhoon is a problem, it can bring large wind load on buildings. Wind force is an important lateral design load for high-rise buildings, especially in interference effects of tall buildings. The interference phenomenon between two adjacent tall buildings involves many parameters, such as distance of the two adjacent buildings, buildings’ geometry shape and the upstream terrain conditions. In this study the Artificial Neural Network technique was applied on an existing limited aerodynamic database to predict tall buildings’ interference effects. The ANN framework includes input layer, output layer and a single hidden layer. The optimal number of neuron was selected through detailed parameter studies. The results indicate that the back-propagation ANN model can predict interference effects of tall buildings up to a reasonable margin of error in terrain A (α=0.32), at least for the initial building design stage. In terrain C (α=0.15), however, there exist significant deviations between ANN predictions and wind tunnel measurements especially in the acrosswind background part. This deviation is likely due to some unidentified errors during wind tunnel measurements.
40
Lin, Yi-Jong, and 林倚仲. "The Interference Effects on the design wind loads of high-rise buildings." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/61395309048341818493.
Full textAbstract:
碩士淡江大學
土木工程學系碩士班
93
High-rise building plays an important role in the city development due to the limited land. In addition to the earthquake force, wind force becomes an important lateral design load for high-rise buildings. The increasing number of high-rise buildings in a large city makes the interference effects between the adjacent buildings becomes an important wind engineering problem. This paper investigates the interference effect on the design wind load of high-rise buildings. The wind tunnel experiments were conducted for different model geometry shapes and various model spacing in a grid system. The wind tunnel experiments can be categorized into two groups: (1) interference effects of inferring buildings with identical volumes but different cross-sectional shapes, (2) interference effects of inferring buildings have the same height but different building width. Design wind load were calculated for comparison. High frequency force balance was used to measure both the mean and dynamic wind loads. The interference factors for mean and dynamic wind loads on both along-wind and across-wind directions were evaluated. The experimental results indicate that the adjacent building casts significant interference effect on the design wind load in general. When the target building was located 3~4 width from the influence of building has the biggest design wind load. The presence of the adjacent building could have noticeable effect on the vortex shedding characteristics and consequently the vortex related wind loads. A design wind load modification procedure in consideration of the interference effects is derived based on the present study. The predicted wind load agrees well with the direct measurement when the geometry of the interfering building has only minor deviation from the model used in the current wind tunnel study.
41
Wang, Chia-Kuo, and 王嘉國. "The Interference Effects on the design wind loads of tall buildings（Ⅱ）." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/80873921611762935556.
Full textAbstract:
碩士淡江大學
土木工程學系碩士班
94
Tall building plays an important role in the city development due to the limited land. In addition to the earthquake force, wind force becomes an important lateral design load for tall buildings. The increasing number of tall buildings in a large city makes the interference effects between the adjacent buildings becomes an important wind engineering problem. This paper investigates the interference effect on the design wind load of tall buildings. The wind tunnel experiments were conducted for different model geometry shapes and various model spacing in a grid system. The wind tunnel experiments can be categorized into two groups: (1) interference effects of inferring buildings with identical volumes but different cross-sectional shapes, (2) interference effects of inferring buildings have the same height but different building width. Design wind load were calculated for comparison. High frequency force balance was used to measure both the mean and dynamic wind loads. The interference factors for mean and dynamic wind loads on both along-wind and across-wind directions were evaluated. The experimental results indicate that the variation of the adjacent building width would cast more influences on the average wind-force than the building height especially when the interfering building locates at X/B =3, Y/B =0. Variation of the width and height of the upstream interfering building would cause significant change in the wind loads of the target building. When the interfering building locates in the region of X/B = 3~13, Y/B =0~4, the dynamic wind loads of the target building would be enhanced except when the interfering building locates very close to the target building. Incorporating the interference factors obtained from this research into the design wind loads for an isolated building, a more realistic and accurate design wind loads can be obtained.
42
Chen, Huang-Chih, and 陳煌志. "The Shielding Effects on the Design Wind Loads of High-rise Buildings." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/18695771343128329480.
Full textAbstract:
碩士淡江大學
土木工程學系
92
High-rise building plays an important role in the city development due to the finite land. Wind force is an important lateral design load other than earthquake force for those high-rise buildings. The increasing number of high-rise buildings in a large city makes the interference effects between the adjacent buildings becoming an important wind engineering problem. This paper studies the shielding effects on the design wind loads of high-rise buildings. The wind tunnel experiments were conducted for different model geometry shapes and the model spacing in a grid system. Two groups of shielding building models were tested: (1) two adjacent buildings have the same height with different width, (2) buildings with the same width, but with different heights. Force balance technique was used to measure both the mean and dynamic wind loads. The shielding factors for mean and dynamic wind loads on both along-wind and across-wind directions were evaluated. The design wind loads at each floor were also calculated for comparison. The experimental results indicate that the adjacent building casts significant shielding effect on the design wind load in general. In the case of different width series, when the target building under the influence of building with width of 1.0b has the biggest design wind load in along-wind and across-wind directions. In the case of different height series, when the adjacent building has height of 1.0H has the biggest design wind load in along-wind directions. When the adjacent building has height of 1.25H has the biggest design wind load in across-wind directions. When both the mean and dynamic shielding effects were taken into consideration, the predicted design wind load based on the empirical prediction model agrees reasonably well with the experimental data.
43
Chen, Cheng-Wei, and 陳正瑋. "Applications of Neural Networks on the Predictions of Interference Effects on Buildings Design Wind Load(Ⅱ)." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/91129659171647637369.
Full textAbstract:
碩士淡江大學
土木工程學系碩士班
96
In large city, tall buildings are usually built in a cluster within the crowded commercial zone, and the interference effects from the adjacent buildings cannot be ignored. Due to the complexity of the interference phenomenon, the building interference phenomenon is too complicated a problem for traditional engineering approaches. A more sensible way to deal with this problem would be using good quality aerodynamic database with IT techniques such as neural network. The aim of this thesis is to construct an aerodynamic database on building interference that can be used together with the wind code or/and single building’s aerodynamic database for wind resistant design of tall buildings. In this study the Artificial Neural Network technique was applied on an existing limited aerodynamic database to predict tall buildings’ interference factor (IF), and use the result to calculate design wind load. The ANN model is radial basis function (RBF) neural network, and the framework includes input layer, a single hidden layer and output layer. By centers and radial basis function in the hidden layer to create a neural network. The results indicate that, in the training phase, the error almost can smaller than 3%, in the predicting phase, except acrosswind background part in terrain C ,the static part and background part in all terrain are less than 10%. The resonant part in terrain A&B are within 10% to 20%. However, in terrain C the error of resonant part can be as large as 20% to 35%. In other words the resonant part need to be further improved.
44
Cheng-ChengTsai and 蔡政晟. "Effects of Composite Layup on Structural Strength under Extreme Wind Load and Optimal Design for Composite Material Blade of a 5MW Wind Turbine." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/93742997119944977853.
Full textAbstract:
碩士國立成功大學
機械工程學系
102
Effects of Composite Layup on Structural Strength under Extreme Wind Load and Optimal Design for Composite Material Blade of a 5MW Wind Turbine Cheng-Cheng Tsai Jen-Fin Lin Department of Mechanical Engineering, College of Industry SUMMARY The structural optimal design of a 61.3 meter long blade in NREL 5MW wind turbine was developed in this thesis for use under extreme wind condition. The blade model was created by Solid Works and simulated in ANSYS using finite element methods. The static extreme wind condition based on IEC-61400 regulation was used for calculating the aerodynamic loads by Blade Element Momentum(BEM) theory in NREL WT-Perf software. In this thesis, single factor analysis, Taguchi method and buckling analysis were used for finding out the effect of layup thickness to the blade structure and optimal layup design. The numerical results will be confirmed to have acceptable performance with regard to weight, tip displacement, maximum strain failure criterion and Tsai-Wu failure criterion, all of above except weight should as well meet the requirements introduced from international regulation such as DNV-OS-J101 from Det Norske Verita(DNV) organization and IEC-61400 from International Standard organization. Key words: Wind turbine blade, Composite material, Sandwich structure, Extreme wind condition, Taguchi method. INTRODUCTION The blades in a wind turbine are key components for capturing wind power, they are very expensive and would affect the safety and efficiency of the wind turbine. According to statistical data from Caithness Windfarm Information Forum[3] Caithness Wind farm Information Forum, Summary of wind turbine accident data to 30 June 2013. Available from: 〈http://www.caithnesswindfarms.co.uk〉.[3], fierce wind cause the most blade failure cases, which would lead to blade damages or blade hittingthe tower due to large tip displacement. Therefore, we would like to discuss the effect of layup thickness to blade weight, tip displacement and failure criteria, and confirm whether the layup design conform to requirements of international regulations or not. In this thesis, a NREL 5MW wind turbine blade[21] was used as a numerical analysis model. This wind turbine was establish by National Renewable Energy Laboratory(NREL) and has taken DOWEC, WindPACT and REpower 6MW wind turbines into consideration. Total weight, blade specification, airfoil, pitch angle distribution and wind turbine specification were revealed in their report. Other related literatures includes: Bazilevset. al.[36] had used finite element method for blade pre-bending analysis, the result showed that multilayer composite material blade was suitable to establish by thin-shell model. Young and Wu[47] had a 3.5 meters blade subjected to ANSYS simulation and pointed out that blade element momentum theory has good efficiency and accuracy on calculating aerodynamic loads. BASIC THEORIES The composite material used in this thesis is EGlass/Epoxy laminate layer composed of EGlassfiber and Epoxy matrix, which is an orthotropic material and has different young’s and shear modulus and Poisson’s ratios in each principal coordinate direction. Sandwich structures, combined EGlass/Epoxy laminates with isotropic foam core, can provide better anti-bending and anti-buckling ability. Maximum strain criterion and Tsai-Wu criterion[56] are used in this thesis. Maximum strain criterion is calculated in terms of strain while Tsai-Wu criterion in terms of stress. Both criteria can be used in orthotropic materials while Tsai-Wu criterion has taken interactions in each principal coordinate stresses into consideration. Tip displacement was regulated in DNV[25] international regulation. The blade tip displacement should meet the requirement of certain percentage of blade-tip-to-tower clearance as blade is not deformed. With regard to NREL 5MW wind turbine specifications, the maximum tip displacement would be 8.572 m in static condition and 6.316 m in operating condition. A Taguchi method[59] and L27 orthogonal array of 5 parameter and 3 levels would be used to find out the contribution of each layup thickness to blade structural strength after single factor analysis. The smaller-the-better quality characteristic was analyzed according to maximum strain criterion and Tsai-Wu failure criterion. NUMERICAL SETTINGS The NREL 5MW composite blade would be subjected to finite element method using ANSYS software, including 65,635 element and 60,109 nodes after mesh generation. The main materials used in this thesis are EGlass/Epoxy laminates and foam core, combining the above two materials would create so-called sandwich structure. The NREL 5MW blade was separated to 17 sections along the blade span and each section composed of 5 parts with different thickness, which are skin thickness, skin core thickness, sparcap thickness, web thickness and web core thickness. All the principal coordinate direction 1 of the composite material would point from the blade root to blade tip. The static extreme wind condition, wind velocity 70m/s and rotor speed 0 rpm based on IEC-61400 regulation, is used as aerodynamic loads, which are evaluated by NREL WT-Perf software, would applied at the 17 sections on the blade as boundary conditions and blade root be set as fixed support for representing the phenomena of connection with the hub. RESULTS AND DISCUSSION The baseline layup thickness can be decide by the result of simulations with regard to weight, tip displacement, and failure criteria. To meet the requirements of international regulation regard to tip displacement and safety factors and weight be less NREL report, the proper baseline layup thickness would be 5mm for each part. Increasing skin thickness, sparcap thickness and web thickness would increase blade weight due to greater cover area and larger density of composite material than foam core. Failure criteria can be lower down by increasing skin core thickness, sparcap thickness and web core thickness, but the decreasing slope would slow down as skin core thickness and web core thickness greater than 25 mm and sparcap thickness greater than 5 mm. The failure criteria of optimal parameter sets obtained from Taguchi method are smaller than corresponding values in the L27 orthogonal array, which means that Taguchi method can be used for optimal design in a given parameters and level range. CONCLUSION From the result of single factor analysis, failure criteria could be decreased by increasing skin core thickness, sparcap thickness and web core thickness. And Taguchi method results showed that the skin thickness and web thickness are the least significant to failure criteria decrease, but increasing the above two thickness could help reducing the tip displacement. From the result of buckling analysis, the structural unstable location happens at sparcap location, 13.5 meters from blade root, down side of the blade, and minimum load factor of the blade can be increased by increasing sparcap thickness.
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Hsin, Li Cheng, and 李正信. "The Energy Dissipation Effects of TMD Installed at Tall Steel Communication Towers under Wind Loads." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/88215825452742981185.
Full textAbstract:
碩士中原大學
土木工程學系
88
The main purpose of the paper is focusing on the tall steel tower with the TMD device researching the dynamic response of under the effect of along-wind and comparing the change and reduction of displacement, acceleration and base reaction to prove that TMD surely works well for the wind vibration control. Tall steel tower with Micro-Wave Antennas is an uncovered softness structure, along-wind is the biggest effect to cause the over react of the tower. Therefore, it’s necessary to reduce the over react of the structure by using the concept of structure control. Within the paper, we mentioned about the best design of the parameter and how we get the along-wind dynamic load by using the formula to transfer the turbulent spectra to continuous time series. To calculate the react of the tower, we simulate the force to the tower with the wind, and analysis the time domain with the Newmark method from direct integration. Through the results of wind vibration control to the tall steel tower. We know that TMD has a good performance of controlling effect under the random wind load. To reduce the response of displacement and acceleration we enhance more safety and comfortability to the people inside the building.
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Karabina, Anastasia Smaro. "Effects of regulatory light chain phosphorylation on mutant and wild-type cardiac muscle myosin mechanochemistry." Thesis, 2015. https://hdl.handle.net/2144/13939.
Full textAbstract:
Cardiac muscle contraction is responsible for pumping blood throughout the body. The cyclical, ATP-hydrolysis dependent interaction of the myosin motor protein with filamentous actin drives muscle contraction. During this process the α-helical neck region of myosin acts as a lever arm, transmitting contractile force between thick and thin filaments by amplifying small conformational changes in the myosin motor domain. The resulting relative displacement of thick and thin filaments causes muscle shortening. The regulatory light chain (RLC) of myosin mechanically supports the lever arm by binding to the myosin heavy chain neck region; this is a crucial interaction in maintaining myosin's ability to produce force and motion. We investigated the role of N-terminal modifications of the RLC in modulating actomyosin contractility at the molecular level. Phosphorylation of the RLC is a naturally occurring post-translational modification of the RLC N-terminus that is important for cardiac function and has been shown to enhance contractility at the cellular level. In contrast, genetic mutations of the RLC that lead to familial hypertrophic cardiomyopathy (FHC) disrupt cardiac function and trigger remodeling of the cardiac muscle structure. We studied two FHC-linked mutations, N47K and R58Q, located in the N-terminus of the RLC in close proximity to the phosphorylation site. Using in vitro motility assays we examined how RLC modifications affect the mechanochemical properties of cardiac β-myosin. We found that the FHC mutations reduced myosin force and power generation, in contrast to RLC phosphorylation which increased myosin force and power for WT and mutant myosins. Phosphorylation of mutant RLC resulted in a restoration of the mutation-induced decreases in contractility to WT dephosphorylated levels. These results point to RLC phosphorylation as a general mechanism to increase force production of the individual myosin motor and as a potential target to ameliorate the fundamental contractile FHC-induced phenotype.
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Dlamini, Mkhonzeni Mazambane, and 杜默仁. "The Effects of Dynamic Load on the LVRT Performance for DFIG Wind Farms and Optimal Sizing and Location of STATCOM for LVRT Enhancement." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/48hzmf.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
106
Wind power is the fastest growing renewable energy source in the world. The global quest for a cleaner environment, improvement in wind turbine technology and government pledges to support renewable energy generation has resulted in significantly high renewable energy penetration in power systems. The high penetration coupled with its intermittency, fluctuation and non dispatchability of renewable power has resulted in shortage of power reserves and system inertia as conventional machines are shrinking in the system. Grid codes specially formulated for renewable energy sources have been enacted by power system operators (PSO) to give grid connection, steady state and dynamic operational guidelines. In this study, the low voltage ride through (LVRT) grid code for wind turbines is considered. The LVRT requirement stipulates that if voltage recovery to 90% of nominal voltage following a fault is slower than the set-times at different sag levels, wind farm could disconnect from the grid. Disconnection of wind power in a heavily constrained system can be catastrophic and need to be avoided as the system has less power reserves. Voltage recovery is greatly affected by dynamic loads. Power systems loads are estimated to be roughly 60% dynamic loads which are mostly induction motors. In this study, a PSS/E CLOD composite load model with motor sub-models are used. Undesired disconnection of wind farms (WF) could be mitigated through LVRT enhancement by static synchronous compensator (STATCOM) device at strategic locations. The optimal STATCOM capacity depends on the actual or anticipated dynamic load proportion in the system and the required voltage recovery time. STATCOM locations are determined through the use of Average Integral Absolute Error (AIAE) of voltage deviation as indices and the capacity is determined to comply with German LVRT grid code voltage recovery requirement. In the study it is shown that dynamic var planning can improve wind turbine uptime, overall system integrity and that a single strategically located dynamic var source could serve several adjacent WFs to reduce costs of LVRT enhancement.
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Lyu-RanWang and 王律然. "Effects of Gust and Turbulence on Transient Loads and Performance of 5MW Wind Turbine Using the IEC Model and Constrained Stochastic Simulation." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/24052806698152175472.
Full textAbstract:
碩士國立成功大學
機械工程學系
102
SUMMARY The effects of gust and turbulence on wind turbines are discussed using IEC model and constrained stochastic simulation. The transient effects of gust are characterized as two parameters, tendency and turbulence intensity. Choosing some sets of tendency and turbulence intensity, generate four different transient velocity series, called NewGust. Including IEC gust, there are five transient velocity series as inlet boundary conditions of wind tunnel in CFD simulation. From results of simulations, the thrust, torque, and mechanical power of rotor are similar to transient inlet velocity series. By observing pressure coefficients on blade surface, as wind velocity comes to maximum, there is no change in boundary layer state on the blade surfaces of location 30%,60%,90%. Compared with different NewGust, the higher Ten, the higher time-averaged lift coefficients. And time-averaged drag coefficients increase when TI increases in all kinds of transient inlet velocity series. According to transient loadings of the wind turbine parts, the effects of gust and turbulence on nacelle and tower are more dominant than those on blades. It is showed that the velocity deficit is higher at downstream distance 0.5DR and 1DR behind wind turbine. And the velocity deficit decrease dramatically at downstream distance 2DR. The largest difference in averaged TI occurs at downstream distance 1DR ~1.5DR , it is showed that the vortex structure breakdown at this region. INTRODUCTION In order to design more efficient and high stability wind turbines, the Aerodynamics simulation of wind turbine is the important topic. Currently, the large -scale wind turbines is the main tendency of wind energy development. From some articles, CFD simulation of wind turbines is almost for the small-scale wind turbines. However, there are few research of CFD simulation for the large-scale wind turbines. And there no research about gust effects on large-scale wind turbines. In view of this, the effects of gust and turbulence on large-scale wind turbines are discussed using CFD simulation. MATERIALS AND METHODS The transient effects of gust are characterized as two parameters, tendency and turbulence intensity. Choosing some sets of tendency and turbulence intensity, generate four different transient velocity series, called NewGust. Including IEC gust, there are five transient velocity series as inlet boundary conditions of wind tunnel in CFD simulation. From pressure and velocity field, the loading and performance of wind turbines in transient velocity series can be calculated. Next, the flow character and transient loading series can do more analysis. RESULTS AND DISCUSSION From results of simulations, the thrust, torque, and mechanical power of rotor are similar to transient inlet velocity series. As wind velocity comes to maximum, the thrust and torque of rotor in IEC gust are higher than those in NewGust. As Ten is 17%, TI increasing, the thrust and torque of rotor increase. However, As Ten is 65%, TI increasing, the thrust and torque of rotor decrease. By observing pressure coefficients on blade surface, as wind velocity comes to maximum, there is no change in boundary layer state on the blade surfaces of location 30%,60%,90%. Because of transient effect of wind velocity rapidly increasing, the negative pressure coefficients of blade surface decrease suddenly. Compared with different NewGust, the higher Ten, the higher time-averaged lift coefficients. And time-averaged drag coefficients increase when TI increases in all kinds of transient inlet velocity series. According to transient loadings of the wind turbine parts, the effects of gust and turbulence on nacelle and tower are more dominant than those on blades. The direction of loading frequently changes with time, which cause more fatigue damages on structure compared with steady wind condition. It is showed that the velocity deficit is higher at downstream distance 0.5DR and 1DR behind wind turbine. And the velocity deficit decrease dramatically at downstream distance 2DR. The largest difference in averaged TI occurs at downstream distance 1DR ~1.5DR , it is showed that the vortex structure breakdown at this region. Consequently, the wake of the region from wind turbine to downstream distance 1DR is classify as near wake. And the wake of the region behind downstream distance 1.5DR is classify as far wake. CONCLUSION As Ten is 17%, TI increasing, the thrust and torque of rotor increase. However, As Ten is 65%, TI increasing, the thrust and torque of rotor decrease. Because of transient effect of wind velocity rapidly increasing, the negative pressure coefficients of blade surface decrease suddenly. Compared with different NewGust, the higher Ten, the higher time-averaged lift coefficients. And time-averaged drag coefficients increase when TI increases in all kinds of transient inlet velocity series. According to transient loadings of the wind turbine parts, the effects of gust and turbulence on nacelle and tower are more dominant than those on blades. The direction of loading frequently changes with time, which cause more fatigue damages on structure compared with steady wind condition. Consequently, the wake of the region from wind turbine to downstream distance 1DR is classify as near wake. And the wake of the region behind downstream distance 1.5DR is classify as far wake.