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1
Reeves, P. "Wind loads on semi-submersible platforms." Thesis, University of Strathclyde, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382429.
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Zhang, Yu Ph D. Massachusetts Institute of Technology Department of Mechanical Engineering. "Wave loads on offshore wind turbines." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100344.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 65).
Ocean energy is one of the most important sources of alternative energy and offshore floating wind turbines are considered viable and economical means of harnessing ocean energy. The accurate prediction of nonlinear hydrodynamic wave loads and the resulting nonlinear motion and tether tension is of crucial importance in the design of floating wind turbines. A new theoretical framework is presented for analyzing hydrodynamic forces on floating bodies which is potentially applicable in a wide range of problems in ocean engineering. The total fluid force acting on a floating body is obtained by the time rate of change of the impulse of the velocity potential flow around the body. This new model called Fluid Impulse Theory is used to address the nonlinear hydrodynamic wave loads and the resulting nonlinear responses of floating wind turbine for various wave conditions in a highly efficient and robust manner in time domain. A three-dimensional time domain hydrodynamic wave-body interaction computational solver is developed in the frame work of a boundary element method based on the transient free-surface Green-function. By applying a numerical treatment that takes the free-surface boundary conditions linearized at the incident wave surface and takes the body boundary condition satisfied on the instantaneous underwater surface of the moving body, it simulates a potential flow in conjunction with the Fluid Impulse Theory for nonlinear wave-body interaction problems of large amplitude waves and motions in time domain. Several results are presented from the application of the Fluid Impulse Theory to the extreme and fatigue wave load model: the time domain analysis of nonlinear dynamic response of floating wind turbine for extreme wave events and the time domain analysis of nonlinear wave load for an irregular sea state followed by a power spectral density analysis.
by Yu Zhang.
S.M.
3
Garber, Jason. "Wind loads on and wind-induced overturning of container cranes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/MQ42064.pdf.
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Barata, Johann. "Evaluation of Wind Loads on Solar Panels." FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/567.
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The current impetus for alternative energy sources is increasing the demand for solar energy technologies in Florida – the Sunshine State. Florida’s energy production from solar, thermal or photovoltaic sources accounts for only 0.005% of the state total energy generation. The existing types of technologies, methods of installation, and mounting locations for solar panels vary significantly, and are consequently affected by wind loads in different ways. The fact that Florida is frequently under hurricane risk and the lack of information related with design wind loads on solar panels result in a limited use of solar panels for generating energy in the “Sunshine State” Florida. By using Boundary Layer Wind Tunnel testing techniques, the present study evaluates the effects of wind on solar panels, and provides explicit and reliable information on design wind loads in the form of pressure coefficient value. The study considered two different types of solar panel arrangements, (1) isolated solar panel and (2) arrays, and two different mounting locations, (1) ground mounted and (2) roof mounted. Detailed wind load information was produced as part of this study for isolated and arrayed solar panels. Two main conclusions from this study are the following:(1) for isolated solar panel with high slopes the wind load for wind angle of attack (AoA) perpendicular to the main axis exhibited the largest wind loads; (2) for arrays, while the outer rows and column were subjected to high wind loads for AoA perpendicular to the main axis, the interior solar panels were subjected to higher loads for oblique AoA.
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Browning, Stephen E. "Computer Program for the Analysis of Loads on Buildings Using the ASCE 7-93 Standard Minimum Design Loads on Buildings and Other Structures." Master's thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/37170.
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A computer program for the analysis of loads on buildings is developed. The program determines wind loads, earthquake loads, and snow loads according to the ASCE 7-93 Standard Minimum Design Loads for Buildings and Other Structures (ASCE 7-93). The program is developed using the object-oriented programming methodology and runs on the Microsoft Windows 95 graphical environment. It is a valuable and useful tool for determining loads on buildings.Master of Engineering
6
Hao, Nguyen Anh. "Parallel lamella dome under wind and snow loads." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/101117.
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A well structured computer program has been developed to perform geometrically nonlinear finite element analysis of space trusses and to study the sensitivity of parallel lamella dome under wind and snow loads. The modified Riks/Wempner method is used to perform the prebuckling and postbuckling analysis. The European Convention for Constructional Steelwork (ECCS code) is used as the code of practice for design wind pressures on domes.
Failures of domes have occurred during snow storms and have attributed to heavy local snow concentrations. Most codes of practice do not provide design wind and snow loads for domes, and a few international codes do show significant differences in the distributions of design wind pressure for domes. Moreover, current design practices for domes do not reflect the possibility of heavy local snow concentrations. Since wind load data is widely varied among the codes, and specific information on local snow concentrations is not available, the study of the behavior of a full-size lamella dome under different wind pressures and various snow distributions will be carried out with the finite element analysis, and critical load combinations will be obtained with the aid of stability boundary. The proposed study is expected to provide guidelines for the determination of critical wind and snow load conditions.M.S.
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Naeiji, Amir. "Wind Loads on Residential Rooftop Solar Photovoltaic Panels." FIU Digital Commons, 2017. https://digitalcommons.fiu.edu/etd/3659.
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Solar energy harvesting using photovoltaic (PV) systems has gained popularity in recent years due to its relative ease of use and its cost efficiency compared to the rest of the clean energy sources. However, to further expand the application of PV systems requires making them more desirable than the other competitive energy sources. The improvement of safety and cost efficiency are requisites for further popularization of PV system application. To satisfy these requisites it is necessary to optimally design the system against the environmental conditions. Wind action is one of the main ambient loads affecting the performance of PV systems. This dissertation aims to investigate the effects of wind load on residential scale roof mounted PV panels and their supporting structures as well as evaluating the structural response of the system to the wind-induced vibration. To achieve these goals, several full- and large-scale experimental tests were performed at the Wall of Wind Experimental Facility at Florida International University (FIU). The wind effects on different PV system and roof configurations were investigated in these tests. The results shed light on the most influential parameters affecting the wind pressures acting on the PV panel surface. In addition, the findings are presented in the form of design pressure coefficients for adoption to future building codes and wind standards. The second phase of the physical testing included the investigation of the actual response of the PV system to the wind action. Because of the dynamic properties of the PV panel, it was expected that the wind induced vibration can affect the dynamic response of the system including the acceleration at the panel surface and support reactions at the racking system to roof interface. To test this theory, two different models of the system were developed, one with the real PV panels and the other one with wooden rigid panels. Comparing the results, it was concluded that the dynamic response of the system was not considerably affected by wind-induced fluctuations. Finally, and to better understand the dynamic response of the system, an analytical model was developed using ANSYS and dynamic analysis was carried out using as input the wind induced pressure data acquired from the physical testing. At the first step, the analytical model was verified by comparing the analytical modal frequencies to the experimental natural frequencies obtained from the hammer test. It was shown that the analytical model can well represent the dynamic properties of the actual model. However, once the reaction output was compared to the loadcell data recorded during the wind tunnel test, there was a considerable discrepancy between the results. It was assumed that the deflection of the supporting structure caused this discrepancy. This assumption was verified and it was concluded that the supporting structure can significantly influence the dynamic response of the system.
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Awad, Ahmed Shawky. "Behavior of FRP chimneys under thermal and wind loads." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39801.pdf.
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Balaramudu, Vasanth Kumar. "Tornado-induced wind loads on a low-rise building." [Ames, Iowa : Iowa State University], 2007.
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Zhang, Yu Ph D. Massachusetts Institute of Technology Department of Mechanical Engineering. "Offshore wind turbine nonlinear wave loads and their statistics." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122220.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 83-86).
Due to the large influence of lateral flexible vibrations on offshore wind turbine foundations and the higher natural frequencies of the offshore wind turbine foundation relative to the dominant frequencies of the linear wave load model, the modeling of the dynamic behavior of the foundation under nonlinear wave loads and analysis of their statistical characteristics have become an important issue for offshore wind turbine design. This thesis derives an approximate model of the nonlinear wave loads in the time domain by Fluid Impulse Theory, verifies it with a boundary element method software WAMIT and validates it with experimental measurements. The load level crossing rates and the load power spectral density is obtained in multiple sea states. The simulated nonlinear wave loads are applied as the forcing mechanism on the offshore wind turbine and its foundation, and the mudline bending moments are computed and compared with experimental measurements. The system identification is conducted by fitting the model with the experimental data using linear regression method. The analytical extreme and fatigue prediction of the offshore wind turbine system are derived and evaluated in waters of finite depth and in multiple seastates. Key words: Nonlinear wave loads, nonlinear wave loads statistics, system identification, extremes and fatigue
Financial support from MIT-NTNU energy initiative program and Statoil
by Yu Zhang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
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SANS, JIMÉNEZ ALEJANDRO, and LÓPEZ ANTONIO RICARDO BARCELÓ. "Characterisation of Waves and Wind Loads on Floating Bridges." Thesis, KTH, Bro- och stålbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-267041.
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Floating bridges are complex and unusual structures. There are very fewfloating bridges built in the world so there is not much information about them. Besides, its condition of floating structure makes it an interdisciplinary structure with maritime and marine engineering.Probably their most peculiar characteristic is that their sustenance is pro duced by floaters and mooring lines that provide special boundary conditions to the structure. The lack of transverse stiffness is also an important feature that makes this structure particularly sensitive to lateral loads. Therefore, the correct definition of the environmental lateral loads is crucial. It is during storms that floating bridges can collapse due to the wind and waves.The aim of this thesis is to deal with the special conditions of floating bridges and to go deep into the theory of wind and waves. With this, it is intended to specify calculation methodologies with which to correctly assess these im portant environmental loads.
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Moussa, Maged Abdel-Ghaffar. "Behaviour of semi-rigid composite connections subject to wind loads." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240964.
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Vieira, Cristiano de Castro. "Structural analysis of a wind turbine blade under operational loads." Instituto Tecnológico de Aeronáutica, 2013. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2860.
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With an increasing demand of energy and its associated costs, it is mandatory that different sources of energy are researched, providing the market with more efficient and economically feasible power options. An alternative to hydroelectric power, dominant in Brazil and receiving more investments every day, Wind Power is still more expensive than other sources. Then, the need to study the design, to model, and to optimize it, arises. The purpose of this work is to present the development of a computational tool intended to aid the preliminary structural design of a Wind Turbine Blade, given the aerodynamic geometry (as span, profile and chords). As an applied example, a 2 MW turbine glass-fiber blade model and operational loads are automatically (batch driven) generated and analyzed concerning stress and deformation. Some iterations are made and a structural resistant and light weighted geometry is defined.
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Janajreh, Isam Mustafa II. "Wavelet Analysis of Extreme Wind Loads on Low-Rise Structures." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30414.
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Over the past thirty years, extensive research has been conducted with the objective of reducing wind damage to structures. Wind tunnel simulations of wind loads have been the major source of building codes. However, a simple comparison of pressure coefficients measured in wind tunnel simulations with full-scale measurements show that the simulations, in general, underpredict extreme negative pressure coefficients. One obvious reason is the lack of consensus on wind tunnel simulation parameters.
The wind in the atmospheric surface layer is highly turbulent. In simulating wind loads on structures, one needs to simulate the turbulent character besides satisfying geometric and dynamic similitudes. Some turbulence parameters that have been considered in many simulations include, turbulence intensities, integral length scales, surface roughness, and frequency spectrum. One problem with these parameters is that they are time varying in the atmospheric boundary layer and their averaged value, usually considered in the wind tunnel simulations, cannot be used to simulate pressure peaks.
In this work, we show how wavelet analysis and time-scale representation can be used to establish an intermittency factor that characterizes energetic turbulence events in the atmospheric flows. Moreover, we relate these events to the occurrence of extreme negative peak pressures.Ph. D.
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Kazacoks, Romans. "A generic evaluation of loads in horizontal axis wind turbines." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28479.
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Thousands of load calculations for wind turbine design have been calculated by manufactures, consultants and certification bodies. These have been done as required to develop and validate specific designs. However, there has not been a general systematic study of trends in loads related to key wind turbine design parameters and external operating conditions. The aim of this thesis is parameterise and quantify trends of extreme and fatigue loads based on systematic modifications of wind turbine characteristics. This thesis is in two main parts. The first part provides an overview of loads calculation methods, flow modelling and approach adopted also considering scaling rules, comparing scaling with similarity and the scaling evident in from commercial world turbines data. The second part presents and evaluates loading trends for extreme and fatigue loads related to systematic alterations of key wind turbine parameters. Three chapters of results investigate the load impacts of blade structural properties, rotor solidity and up-scaling respectively. The chapter on blade structural properties demonstrates that the self-weight of blades is a major component influencing loads of the blade root and hub. The chapter on rotor solidity shows that significant load reduction can result for blade root, shaft and yaw bearing in reducing the solidity of rotor. However, the aerodynamic damping reduces with reducing solidity, which is crucial for tower base fore-aft loads; therefore the reducing rotor solidity has an adverse impact on the tower base fore-aft loads. The chapter on up-scale demonstrates that up-scaling with similarity method can give good prediction of loads with an error of ±10% and ±15% for extreme and fatigue loads of large wind turbines (up to 10MW) at the mean wind speed within power production range. Additional, the chapter of up-scaling showed that the up-scaled wind turbines reduce the sensitivity to turbulence with the size of rotor.
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Schmidt, Sarah Ruth. "Computational and wind tunnel studies of shelterbelts for reduction of wind flow and wind-induced loads on low-rise buildings." [Ames, Iowa : Iowa State University], 2008.
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Dagnew, Agerneh. "Computational Evaluation of Wind Loads on Low- and High- Rise Buildings." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/802.
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Buildings and other infrastructures located in the coastal regions of the US have a higher level of wind vulnerability. Reducing the increasing property losses and causalities associated with severe windstorms has been the central research focus of the wind engineering community. The present wind engineering toolbox consists of building codes and standards, laboratory experiments, and field measurements. The American Society of Civil Engineers (ASCE) 7 standard provides wind loads only for buildings with common shapes. For complex cases it refers to physical modeling. Although this option can be economically viable for large projects, it is not cost-effective for low-rise residential houses.
To circumvent these limitations, a numerical approach based on the techniques of Computational Fluid Dynamics (CFD) has been developed. The recent advance in computing technology and significant developments in turbulence modeling is making numerical evaluation of wind effects a more affordable approach. The present study targeted those cases that are not addressed by the standards. These include wind loads on complex roofs for low-rise buildings, aerodynamics of tall buildings, and effects of complex surrounding buildings. Among all the turbulence models investigated, the large eddy simulation (LES) model performed the best in predicting wind loads. The application of a spatially evolving time-dependent wind velocity field with the relevant turbulence structures at the inlet boundaries was found to be essential. All the results were compared and validated with experimental data. The study also revealed CFD’s unique flow visualization and aerodynamic data generation capabilities along with a better understanding of the complex three-dimensional aerodynamics of wind-structure interactions.
With the proper modeling that realistically represents the actual turbulent atmospheric boundary layer flow, CFD can offer an economical alternative to the existing wind engineering tools. CFD’s easy accessibility is expected to transform the practice of structural design for wind, resulting in more wind-resilient and sustainable systems by encouraging optimal aerodynamic and sustainable structural/building design. Thus, this method will help ensure public safety and reduce economic losses due to wind perils.
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Habte, Filmon Fesehaye. "Database-Assisted Analysis and Design of Wind Loads on Rigid Buildings." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2573.
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The turbulent nature of the wind flow coupled with additional turbulence created by the wind-building interaction result in highly non-uniform, fluctuating wind-loading on building envelopes. This is true even for simple rectangular symmetric buildings. Building codes and standards should reflect the information on which they are based as closely as possible, and this should be achieved without making the building codes too complicated and/or bulky. However, given the complexity of wind loading on low-rise buildings, its codification can be difficult, and it often entails significant inconsistencies. This required the development of alternative design methods, such as the Database-Assisted-Design (DAD) methodology, that can produce more accurate and risk-consistent estimates of wind loads or their effects.
In this dissertation, the DAD methodology for rigid-structures has been further developed into a design tool capable of automatically helping to size member cross sections that closely meet codified strength and serviceability requirements. This was achieved by the integration of the wind engineering and structural engineering phases of designing for wind and gravity loads. Results obtained using this method showed DAD’s potential for practical use in structural design. Different methods of synthesizing aerodynamic and climatological data were investigated, and the effects of internal pressure in structural design were also studied in the context of DAD. This dissertation also addressed the issues of (i) insufficiently comprehensive aerodynamic databases for various types of building shapes, and (ii) the large volume (in size) of existing aerodynamic databases, that can significantly affect the extent to which the DAD methodology is used in engineering practice.
This research is part of an initiative to renew the way we evaluate wind loads and perform designs. It is transformative insofar as it enables designs that are safe and economical owing to the risk-consistency inherent in DAD, meaning that enough structural muscle is provided to assure safe behavior, while fat is automatically eliminated in the interest of economy and CO2 footprint reduction.
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Bysice, Jason. "In-Situ Measurement of Wind Loads for Roof Edge Metal Configurations." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33002.
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The role of a roof on any building is to separate the interior environment of the building from the exterior environment, thereby making it a crucial component of the building design. Metal roof edges are the first line of defense against wind-induced loads on the roof system; however, data on the nature of these loads acting on the roof edge system is scarce. Previous studies with field measurements of wind pressure acting on the roof edge reported that metal flashings experienced negative pressure. These findings suggest that current building codes in North America (i.e. NBCC and ASCE codes) do not accurately identify wind design loads acting on roof edge systems. The Roof Edge Systems and Technologies (REST) project is a consortium of academia, government and roof industries, which was created to develop testing protocols and design guidelines for roof edges. The work presented in this thesis contributes to the collection and analysis of wind loads acting on metal roof edges, which were installed on the Canada Post building in Vancouver, Canada. The thesis presents the findings and analysis of the measured wind-induced pressure acting on all surfaces of three different edge configurations, namely the Anchor Clip Configuration (ACC), Continuous Cleat Configuration (CCC) and Discontinuous Cleat Configuration (DCC). The analysis showed the presence of negative pressure acting on all three faces of the configurations, in which the type of configuration had minimum effect on the magnitude and nature of the wind-induced loads. Furthermore, the top face of the edge configurations was found to experience the highest suction, and the front face of the edge coping was subjected to a net outward suction force due to the combination of the suction experienced by the coping front face and the positive pressure acting on the cleat. Comparison of these results with current NBCC and ASCE building codes highlight a need to update these codes in order to adequately design metal roof edges against wind action.
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Rocha, Daniel. "RELIABILITY OF LIGHT-FRAME WOOD ROOF CONSTRUCTION UNDER EXTREME WIND LOADS." MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07082005-125227/.
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Light-frame wood construction is frequently used in the U.S. High wind events, such as hurricanes, may cause severe damage to these structures by breaking the roof envelope. This study focuses on computing reliability indices of roof sheathing panels exposed to high wind events while considering a time and spatially varying wind load. A procedure is developed that links probabilistic and dynamic finite element analysis codes. The results show that a few critical panels are most susceptible to damage, while most panels have significantly higher reliability indices than previous studies based on simplified analyses have shown. By setting a target reliability index, panel nail spacing can be adjusted to provide a more uniform level of safety over the entire roof.
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Jonkman, Jason Mark. "Dynamics modeling and loads analysis of an offshore floating wind turbine." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3284496.
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Irtaza, H. "Experimental and computational determination of wind loads on netted/sheeted scaffolds." Thesis, Oxford Brookes University, 2009. https://radar.brookes.ac.uk/radar/items/06628cd5-580a-481d-b557-57e598653394/1/.
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This thesis describes an investigation into the wind loading on access scaffolds erected around a cubical building, clad by impermeable sheeting or permeable debris netting. The subject was investigated experimentally by tests in a wind-tunnel and theoretically using computational fluid dynamics techniques. The results were verified from the wind tunnel tests and computational analyses on the Silsoe Experimental Building (SEB) using data from the full-scale tests made in 1993-94 at Silsoe, U.K. The lower portion of the Atmospheric Boundary Layer exhibits different flow properties to the upper elevations. A procedure is presented for modelling the atmospheric surface layer flow properties in a boundary-layer wind-tunnel at useful model scales. The full-scale data available from the cubical 6m x 6m x 6m SEB was used to validate the results presented in this study. A model scale of 1:30 were used both for experiments in a wind-tunnel and in the computational analyses undertaken in the study. Pressure data obtained from the wind-tunnel experiments on the SEB model were compared to full-scale data with good agreement. These data were also compared with various computational fluid dynamics techniques available commercially and the conclusions drawn on the use of the different techniques. The wind-tunnel simulations on an SEB model and on a sheet/elevated sheet clad scaffold models were undertaken based on a duplication of the turbulence intensities and small-scale turbulence of the incidence flow. It is very difficult to achieve equality of Reynolds number in the wind-tunnel as it is very difficult to achieve exactly the same integral scales of turbulence. Two different types of terrain and inflow boundary conditions were simulated in the wind-tunnel for the models and results are reported here. Large suctions (separation of flows) occur near the leading edges and roof corners. The modelling of these phenomena in the wind-tunnel remains a problem. Because of the limited space near the corners and leading edges, it is difficult to make reliable measurements by introducing probes in these areas. This difficulty can be overcome by modelling the flow with Large Eddy Simulation (LES) numerical techniques. However, the disparity between the large and small scales, especially under extreme wind conditions, makes it extremely difficult to resolve the entire range of dynamic scales. The pressure force on bare pole access scaffolds are further influenced by the presence of the building façade which induces a shielding effect. A 2-D model of bare pole scaffolds surrounding the SEB using CFD techniques was successfully achieved whereas a 3-D model could not be produced because of the limitations of the meshing-software GAMBIT available to the author. Cladding increases the wind loads on scaffold structures above the pressure force on bare pole access scaffolds. To determine the wind forces on net/sheet clad scaffolds the Silsoe Experimental Building was used as a base model and simulated scaffolds erected around it. Although, sheeting/netting exhibits aero-elastic behaviour under wind load, an assumption was made to treat the cladding (sheeting/netting) surrounding the scaffold as being made of static solid thin plates. Models were tested in a wind-tunnel and the same assumptions were used in the computational fluid dynamics analyses. For the sheet clad scaffolds, two models were made, one with sheeting touching the ground and the other with an elevated sheet surrounding the building. These models were tested in a wind-tunnel to determine the pressure coefficients on the outer and inner faces of the sheeting. The permeability of the two types of net were successfully obtained from wind-tunnel tests. The simulated data from the wind-tunnel tests were used as input for different computational techniques with good agreement. A new procedure was developed to extend the computational model to net clad scaffolds (both elevated and touching the ground) with the netting simulated as porous media. The author presents new results of the pressure coefficients on sheeted scaffolds obtained using CFD and wind-tunnel techniques and also CFD results on netted scaffold structures. This thesis is the result of research undertaken to assess various methods available for the numerical simulation of turbulent fluid flow using the Fluent Software Package and to see their applicability in computational wind engineering. Investigations have concentrated on analysing the accuracy and numerical stability of a number of different turbulence models including both widely available models and state of the art techniques. Furthermore, Large Eddy Simulations using the dynamic kinetic energy sub-grid-scale model have been completed on some models, in order to account for the four dimensional nature of turbulent flow and to show the best correlation between wind-tunnel, full-scale and sheeted scaffolds. The author has detailed and tested all the above techniques and gives recommendations on the appropriate turbulence model to be used for successful computational wind engineering. Finally the author has given recommendations on the wind pressures to be used in analysing the scaffold structures.
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Douglas, Mary Keith. "Sensitivity of Steel Purlins to Changes in Application of Wind Loads." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99140.
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This project studied the effects of wind tunnel test loads applied to purlins in low rise steel buildings compared to those determined with currently recognized wind loading provisions. The National Institute of Standards and Technology (NIST) database of low-rise building wind tunnel test data, which was collected at the University of Western Ontario (UWO) boundary layer wind tunnel, was used to model a realistic wind load scenario. Pressure coefficient data recorded in the database was applied statically to individual purlins in a typical design for the size of buildings studied. These results were then compared to those obtained using the wind design provisions in ASCE 7-16 Chapter 30 for Components and Cladding. The primary data of interest was shear and moment values along the length of the purlins, which were modeled as continuous beams. Comparisons were made between the resultant shear and moment from both the wind tunnel load and ASCE 7-16 load values at 1-foot increments along the length of the purlin. The results showed that the overall peak values obtained from wind tunnel test loads were 3% to 49% higher than those calculated using ASCE 7-16 for purlins that were on the windward edge of the building. Purlins on the interior of the building varied in whether they exceeded the loads calculated with ASCE 7. Changing the height of the structure and the terrain roughness both increased the number of purlins that were lower than the values provided in ASCE 7-16 in the interior of the structure.Master of Science
Purlins are roof members used in low rise steel buildings to transmit wind loads applied to the roof of the structure to the frame of the building. This project studied the effects of applying loads to purlins using methods specified by the code compared to those found in a wind tunnel, to look at the similarity of the values and model the actual behavior of the purlins more accurately. For this study, wind tunnel test data obtained from the National Institute of Standards and Technology (NIST) database was applied to the purlins and the shear and moment was calculated. These results were compared to the current code requirements provided in the American Society of Civil Engineers (ASCE) 7 document: Minimum Design Loads and Associated Criteria for Buildings and Other Structures. The results showed that the loads developed in the purlins subjected to wind tunnel test loadings were 3% to 49% higher on the edge of the building than those that had the ASCE 7 design loads applied. More accurately modeling the behavior of the purlins using wind tunnel test data and beam models showed that in locations where the purlins received the maximum wind force, the ASCE 7 requirements for components and cladding tended to be lower than the wind tunnel test data. However, in locations where the purlins were not experiencing the maximum wind force, the ASCE 7 requirements tended to overpredict the loads, based on the use of symmetric high wind areas to design for all wind angles.
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Kim, Hongjin. "WAVELET-BASED ADAPTIVE CONTROL OF STRUCTURES UNDER SEISMIC AND WIND LOADS." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039128747.
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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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Humphreys, Nicholas David. "High cross wind gust loads on ground vehicles from moving model experiments." Thesis, University of Nottingham, 1995. http://eprints.nottingham.ac.uk/11923/.
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The environmental wind tunnel at Nottingham University has been extended so that realistic mean hourly atmospheric boundary layers can be generated at sufficient scale to allow aerodynamic tests of sharp edged vehicles to be undertaken. A moving model rig owned by British Rail Research was installed perpendicular to the flow near the end of the working section. As part of this project an automatic refiring mechanism was developed allowing some 2000 transits of vehicles incorporating an internal balance and data logger to be made across the working section with a realistic mean hourly atmospheric boundary layer present. The quality of the data from the moving model rig was assessed. Moving model rig tests and static model tests of a 1/50th scale lorry and 1/45th railway container vehicles have been conducted and extreme value forces and moments relevant to the gust time that overturn a vehicle were calculated. These are the first measurements to have been made using a realistic mean hourly ABL and modelling the vehicle's movement. This thesis assesses the usefulness of the normalised extreme force parameter in determining the extreme forces that a full scale moving vehicle experiences. It was found that the normalised extreme force parameter remains invariant with model time scale for the range of times considered. Further for both the moving model rig tests and the static tests the value of unity that this parameter takes for yaw angles above 30 degrees implies quasi steady behaviour without additional body induced unsteadiness. At lower yaw angles, however, some body induced unsteadiness is evident. These conclusions are compared with predictions from existing numerical models and previous experimental tests. The measured lift force from the static tests compared with the moving model rig tests at 90 degrees yaw angle, i. e. with the moving model stationary, shows a large difference. This is not understood and two concerns are expressed: the effect of the slot, through which the supports of the moving model travel, beneath the vehicle, may be altering the pressure in this region; or it could be due to a Reynolds number effect caused by the small underbody height above the ground.
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Mohammadi, Mohammad Mehdi. "PREDICTION OF WIND TURBINE BLADE FATIGUE LOADS USING FEED-FORWARD NEURAL NETWORKS." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444115.
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In recent years, machine learning applications have gained great attention in the wind power industry. Among these, artificial neural networks have been utilized to predict the fatigue loads of wind turbine components such as rotor blades. However, the limited number of contributions and differences in the used databases give rise to several questions which this study has aimed to answer. Therefore, in this study, 5-min SCADA data from the Lillgrund wind farm has been used to train two feed-forward neural networks to predict the fatigue loads at the blade root in flapwise and edgewise directions in the shape of damage equivalent loads.The contribution of different features to the model’s performance is evaluated. In the absence of met mast measurements, mesoscale NEWA data are utilized to present the free flow condition. Also, the effect of wake condition on the model’s accuracy is examined. Besides, the generalization ability of the model trained on data points from one or multiple turbines on other turbines within the farm is investigated. The results show that the best accuracy was achieved for a model with 34 features, 5 hidden layers with 100 neurons in each hidden layer for the flapwise direction. For the edgewise direction, the best model has 54 features, 6 hidden layers, and 125 neurons in each hidden layer.For a model trained and tested on the same turbine, mean absolute percentage errors (MAPE) of 0.78% and 9.31% are achieved for the flapwise and edgewise directions, respectively. The seen difference is argued to be a result of not having enough data points throughout the range of edgewise moments. The use of NEWA data has been shown to improve the model’s accuracy by 10% for MAPE values, relatively. Training the model under different wake conditions did not improve the model showing that the wake effects are captured through the input features to some extent. Generalization of the model trained on data points from one turbine resulted in poor results in the flapwise direction. It was shown that using data points from multiple turbines can improve the model’s accuracy to predict loading on other turbines.
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Pesmajoglou, Stelianos. "Three-dimensional wake computations applied to horizontal axis wind turbines." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367829.
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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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Fischer, Tim [Verfasser]. "Mitigation of Aerodynamic and Hydrodynamic Induced Loads of Offshore Wind Turbines / Tim Fischer." Aachen : Shaker, 2012. http://d-nb.info/1052408753/34.
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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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Chan, Godine Kok Yan. "Computation of nonlinear hydrodynamic loads on floating wind turbines using fluid-impulse theory." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104254.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 199-202).
Wind energy is one of the more viable sources of renewable energy and offshore wind turbines represent a promising technology for the cost effective harvesting of this abundant source of energy. To capture wind energy offshore, horizontal-axis wind turbines can be installed on offshore platforms and the study of hydrodynamic loads on these offshore platforms becomes a critical issue for the design of offshore wind turbine systems. A versatile and efficient hydrodynamics module was developed to evaluate the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation - the Fluid Impulse Theory(FIT). The new formulation allows linear and nonlinear loads on floating bodies to be computed in the time domain, and avoids the computationally intensive evaluation of temporal and spatial gradients of the velocity potential in the Bernoulli equation and the discretization of the nonlinear free surface. The module computes linear and nonlinear loads - including hydrostatic, Froude-Krylov, radiation and diffraction, as well as nonlinear effects known to cause ringing, springing and slow-drift loads - directly in the time domain and a stochastic seastate. The accurate evaluation of nonlinear loads by FIT provides an excellent alternative to existing methods for the safe and cost-effective design of offshore floating wind turbines. The time-domain Green function is used to solve the linear and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loads is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently.
by Godine Kok Yan Chan.
Ph. D.
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Devaney, Louise Claire. "Breaking wave loads and stress analysis of jacket structures supporting offshore wind turbines." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/breaking-wave-loads-and-stress-analysis-of-jacket-structures-supporting-offshore-wind-turbines(acef8efd-eae2-4a52-9513-b2873e7a3a25).html.
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In terms of future power generation in UK and Germany, offshore wind is the next big player with 40GW and 32GW capacity planned for installation in both countries respectively by 2030. The latest Round 3 of sites owned by the Crown Estate explore deeper water depths of up to 78m in the Irish Sea. Foundations for offshore wind structures consume around 25% of the total project cost therefore the design of support structures is the subject of this thesis. The current state-of-the-art support structure options available for offshore wind turbines have been outlined in this thesis with an evaluation of the preliminary design of monopile and jacket solutions. This assessment resulted in further studies into the loading acting on a monopile foundation along with research into the fatigue design of multiplanar tubular joints for jacket structures. Mathematical modelling of linear and nonlinear waves combined with the Morison equation was completed to check the effects of breaking waves on a monopile foundation. Results indicated that measured forces were up to a factor of 2.5 times greater than calculated values, which suggests that loads could be under predicted if the effects of breaking are not considered. The theoretical maximum wave height before breaking was then linked to wind speed and a comparison of overturning moments from the two loads was made. Wave loads dominated at water depths of around 30m for lower wind speeds but this depth decreased to around 12m as wind speeds approached cut-out of 25m/s. For deeper water depths and larger capacity turbines, jackets are the preferred design solution. Joint design in FLS is the critical aspect of jacket design with castings often required to provide adequate capacity. A review of stress concentration factors (SCF) for tubular joints indicated that the coded approach, which uses SCF equations for uniplanar joints, could be missing the multiplanar effects. Finite element (FE) modelling of multiplanar tubular joints was completed using ANSYS Workbench to examine the effects of loading in out-of plane braces. Carry-over of stress from the loaded brace of the joint to unloaded neighbouring braces was observed which implies the importance of modelling joints as multiplanar geometries. A parameter study in ANSYS Workbench covering 1806 different geometrical configurations and loads was carried out with a regression of the data to give new sets of SCF equations for multiplanar tubular joints. SCFs from these equations were improved compared to Efthymiou but difficulties were encountered when superimposing the output (including Efthymiou). Further work on the superposition of individual load cases was therefore recommended for future work.
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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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Papagiannis, Michail. "WIND TURBINE FOUNDATIONS IN CLAY : Technical and economic considerations for proposals for wind turbine foundations." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353397.
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This thesis approaches the problem of the cost-efficient wind turbine foundation on an onshore site of clayey soil characteristics. The given soil stratigraphy includes a layer of clay and two sands of different density. The characteristics of the soil and the water level that were used as input come from a site in Peloponissos, Greece. The applied wind, static and seismic loads on this study were resolved with the German DIN standards, and other related research and European standards. The safety factors were adjusted for wind turbines. For the pile solution, after the bearing and overturning adequacy against the horizontal and vertical loads was proven with the calculation of the DIN equations, then the model was inserted in the Pfahl program using DIN 4017 equations to calculate settlements. Firstly, a shallow foundation of various dimensions in the clay layer over the water level with all the necessary checks was considered. Afterward, a deep foundation solution of a single bored pile, with reinforcement steel casing, of various diameters was investigated. The different foundation solutions were assessed and compared on a technical and economic basis. As a conclusion, the 0.70 meter diameter single pile was chosen as the best solution because it needs only a few days for construction, and it is the most cost-efficient. The chosen circular footing was of a diameter of 10 meters and 1.5 meter raft thickness, but proved unfeasible because of high excavations costs. The checks on the DIN standards and Eurocode that set the boundaries for the design in the two cases were recognised and possible future work goals were discussed.
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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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Vasquez, Arango Juan Felipe [Verfasser], Robert [Akademischer Betreuer] Pitz-Paal, and Michael [Akademischer Betreuer] Breuer. "Dynamic wind loads on heliostats / Juan Felipe Vasquez Arango ; Robert Pitz-Paal, Michael Breuer." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/113087172X/34.
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Chiu, Tak Wai. "Aerodynamic loads on a railway train in a cross-wind at large yaw angles." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358612.
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Mazaheri, Said. "Response based analysis of an FPSO due to arbitrary wave, wind and current loads." Thesis, University of Newcastle upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289168.
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Ivanco, Thomas Glen. "Development and Validation of an Aeroelastic Ground Wind Loads Analysis Tool for Launch Vehicles." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34462.
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An analytical modal response tool was developed to investigate the characteristics of and to estimate static and dynamic launch vehicle responses to ground wind loads (GWL). The motivation of this study was to estimate the magnitude of response of the Ares I-X launch vehicle to ground winds and wind-induced oscillation (WIO) during roll-out and on the pad. This method can be extended to other launch vehicle designs or structures that possess a nearly cylindrical cross-section. Presented in this thesis is an overview of the theory used, a comparison of the theory with wind tunnel data, further investigation of the data to support the assumptions used within the analysis, and a prediction of the full-scale Ares I-X response. Additionally, an analytical investigation is presented that estimates the effect of atmospheric turbulence on WIO response.
Most of the wind tunnel data presented in this report is taken from the GWL Checkout Model tested in the NASA Langley Transonic Dynamics Tunnel (TDT) in April 2007. The objective of the GWL Checkout Model was to reestablish and evaluate the capability of the facility to conduct GWL testing and to operate the associated equipment. This wind tunnel test was not necessarily intended to predict the full scale Ares vehicle response to GWL; however, it can be used to help validate the newly developed analytical method described in this thesis.
A detailed GWL test incorporating updated vehicle designs and launch pad configurations of the Ares I-X flight test vehicle was also conducted in the TDT during the fall of 2008. This test provides more accurate predictions of the second bending mode response of the Ares I-X, and it models effects of the nearby tower and support structures. The proposed analytical method is also compared to select data from the Ares I-X GWL test; however, it is presented as normalized values to protect the sensitivity of the data.
Results of the proposed analytical method show reasonable correlation to wind tunnel data. Also, this method was the first to determine that second bending mode WIO response was not only possible for the Ares I-X, but will also produce the most critical loads. Finally, an explanation is offered in this thesis regarding discrepancies between wind tunnel and full-scale WIO response data.Master of Science
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Kumar, Nikhil. "Stress analysis of wood-framed low-rise buildings under wind loads due to tornados." [Ames, Iowa : Iowa State University], 2008.
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Sivapathasundaram, Mayooran. "Localised pull-through failures of thin steel roof battens subject to wind uplift loads." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/204638/1/Mayooran_Sivapathasundaram_Thesis.pdf.
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High wind events such as tropical cyclones, severe storms and tornadoes are more likely to impact the Australian coastal regions due to possible climate changes. Such events can be extremely destructive to building structures, in particular, low-rise buildings with lightweight roofing systems that are commonly made of thin steel roof sheeting and battens. Large wind suction loads that act on the roofs during high wind events cause premature failures of roof connections (fixings), leading to complete roof failures.
Past wind damage investigations showed that the roof sheeting to batten connection failed frequently during high wind events. These local connection failures have been extensively investigated by many researchers and suitable recommendations to eliminate such failures have been proposed. However, this meant the weakest point has now shifted to the batten to truss/rafter connection. These connections are predominantly subjected to localised pull-through failures in which the screw fastener head pulls through the bottom flanges of thin steel roof battens. However, these failures have not been investigated adequately despite the many roof batten pull-through failures and eventual losses of both roof sheeting and battens observed after recent high wind events. Currently available design rules for the pull-through capacity of cold-formed steel screw fastener connections do not address the specific pull-through failures in thin steel roof battens under wind uplift loading. Current design practice of roof battens is based on using the design wind uplift capacity tables published by their manufacturers. However, it is unclear whether these design capacity tables developed for specific roof battens adequately included the effects of pull-through failures.
As for the roof sheeting to batten connections, batten to rafter/truss connections are also subjected to both static and fatigue failures due to static and cyclic wind uplift loads, respectively. Although some experimental studies were conducted in the past using simulated static and cyclic wind loading, they were incomplete and no design rules were developed. Since the climate predictions indicate the likelihood of severe storm events with increased intensity in the future, they are more likely to cause static pull-through failures of roof battens. In addition, a thorough understanding of the static behaviour is first needed to evaluate the fatigue behaviour in depth. Hence this research was aimed at investigating the localised pull-through failures of thin steel roof battens under simulated static wind uplift loads, using laboratory experiments and finite element modelling.
A preliminary and detailed experimental study was first conducted using industrial roof battens and full scale air-box tests and three small scale tests such as two-span batten tests, cantilever batten tests and short batten tests. Suitable small scale test methods were identified to accurately simulate the localised pull-through failures of roof battens. The applicability of the proposed small scale test methods for other roof battens was verified using two-span and short batten tests undertaken using roof battens made at the university workshop. Based on the test results, a suitable modification factor was recommended for use with the pull-through capacity equation presented in the current Australian (AS/NZS 4600: 2005) and American (AISI S100: 2012) cold-formed steel standards to accurately determine the pullthrough failure loads of roof battens.
The main and extensive experimental study was then undertaken using two-span and short batten tests to examine the pull-through failures of roof battens. The tests were conducted to investigate the effects of many critical parameters such as screw fastener tightening, batten height, web angle, steel grade, batten thickness, screw fastener head size, screw fastener location, batten bottom flange width, underside and edge details of the screw fastener head, and screw fastener types on the roof batten pull-through failure behaviour and capacity. Since the test results showed that the pull-through failure behaviour of high strength and low strength steel roof battens significantly differed from each other due to the differences in ductility, two new design rules and relevant capacity reduction factors were developed to accurately determine the design pull-through capacities of roof battens.
The finite element models of both two-span batten and short batten test specimens were modelled and analysed using ABAQUS software. A suitable failure criterion was developed based on constitutive model inputs and employed in the finite element analyses to accurately predict the initiation of pull-through failures of thin steel roof battens associated with the tearing fracture of bottom flange around the screw fastener head edge. The finite element models were validated using the test results, and additional parametric studies were conducted to investigate the parameters which were not considered in the experimental study due to their lower importance on pullthrough failure behaviour and capacity of roof battens. A large pull-through capacity data base was developed using the pull-through failure loads obtained from the tests and finite element analyses. Suitable design rules were then developed using them and finally recommended with suitable capacity reduction factors for the accurate determination of the design pull-through capacities of thin-walled steel roof battens.
This study also investigated the strengthening methods recommended by the roof batten manufacturers and builders and showed that they are inadequate to provide a significant improvement based on the governing pull-through failures of roof battens.
A reliable strengthening method using overlapping short battens as brackets at the supports was recommended and a series of roof batten tests was conducted using two-span batten tests and two types of industrial roof battens. The test results confirmed the adequacy of the proposed strengthening method.
Suitable fragility curves were developed using detailed probabilistic analyses and Monte Carlo simulations based on the governing pull-through failures of thin steel roof battens to predict the likely level of roof damages to a large community for a given wind speed. The pull-through failure behaviour of roof battens was examined by defining eight different cases that are likely to occur during high wind events (for example, with and without dominant openings) and developing relevant fragility curves. The effects of using different batten span and spacing were also investigated using fragility curves. Fragility curves were also used to evaluate the enhancement level that could be achieved with the proposed strengthening method.
In summary, this research study has developed suitable test, design and strengthening methods and fragility curves for thin steel roof battens subject to localised pullthrough failures under high wind uplift loads.
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Giles, Tyler Eric. "Ductile Design and Predicted Inelastic Response of Steel Moment Frame Buildings for Extreme Wind Loads." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9161.
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Inelastic design methods have been used in seismic design for several years and are well accepted in engineering practice. In contrast, an inelastic wind design method is yet to be developed, in part due to the inherent differences between seismic forces and wind forces. Current wind design practice follows a linear method to find a design windspeed for the location where the structure will be built. Once the design windspeed has been determined, the lateral force resisting system is designed such that it will behave elastically. This study was conducted with the hypothesis that by providing ductility at the material level, member level, and system level it may be possible to use a reduced design force for wind (i.e., a design force reduction that is proportional to a wind response modification factor). A three-story office building that uses steel moment frames as the primary lateral force resisting system was examined to test the hypothesis. Various levels of ductility were included based on ductility requirements for material strength, section stability and system stability originally developed for seismic design. Moment frames were designed for a range of design windspeeds and for three levels of ductility. For each design windspeed, a non-ductile (representing the moment frame as it would be designed by current standards), moderately-ductile and highly-ductile moment frame were developed. A finite element model of the building was made to capture inelastic material behavior and large displacements. The finite element model was subjected to wind loads based on wind tunnel tests data, and the static pushover, vibration, and dynamic responses of the building were evaluated. The performance of each moderately-ductile and highly-ductile moment frame was compared to the performance of each non-ductile frame of a higher design windspeed. The results show that for moderately-ductile moment frames, a wind response modification factor equal to 2 provided a collapse capacity that met or exceeded the collapse capacity of the comparative nonductile moment frame. For highly-ductile moment frames, a wind response modification factor equal to 3 met or exceeded the collapse capacity of the comparative non-ductile moment frame. In many instances, the collapse capacity of the moderately-ductile moment frame was similar to the collapse capacity of the highly-ductile moment frame. Thus, the results indicate that the use of a response modification factor for wind may be viable.
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Wijesooriya, Kasun Danushka. "An Uncoupled Fluid-Structure Interaction Numerical Framework to Estimate Wind Induced Loads on Super-tall Structures." Thesis, University of Sydney, 2021. https://hdl.handle.net/2123/24515.
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The study of wind induced loads on super-tall structures has been a widely researched topic within the field of Civil, Structural and Wind engineering communities. As these super-tall structures become more complex in terms of structural design, the need for wind tunnel tests such as aeroelastic modelling becomes a requirement. However, aeroelastic wind tunnel tests are often overlooked at the conception of a project due to the complexity associated with the test procedure. As a result, an alternate method in terms of numerical simulations is highly sought for industrial applications. To this end, this thesis presents a numerical framework to estimate structural responses of wind sensitive slender super-tall structures. The framework consists of a Fluid-Structure Interaction (FSI) approach where Computational Fluid Dynamics (CFD) is used to predict wind induced loads on the structure and a transient Structural analysis is performed to estimate structural responses. The numerical framework which is presented in this thesis is complimented with three experimental tests performed in a Boundary Layer Wind Tunnel (BLWT) for validation purposes. The CFD numerical technique proposes the use of an Embedded-Large Eddy Simulation (ELES) and it is shown that the method can achieve similar accuracy at a fraction of the cost that is required for a Large Eddy Simulation (LES) analysis. The core of the framework proposes a novel, and highly efficient pressure mapping technique, where an uncoupled one-way FSI simulation is presented. The numerical framework is critically evaluated against existing numerical methods and an aeroelastic multi-degree of freedom (MDOF) wind tunnel test. It is shown that the proposed method is capable of predicting similar structural response in a time efficient manner. In conclusion, this thesis provides a comprehensive numerical framework which can be readily adopted by designers to determine structural responses of wind sensitive structures.
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Tian, Lin. "Analysis of Time-Varying Characteristics of Simulated Turbulence in Wind Tunnel." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/33717.
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Eight roughness configurations in Clemson boundary layer wind tunnel are presented. For these configurations, flow parameters such as turbulent intensities, integral length scales, large- and small- scale turbulence, and spectra of velocity components of the wind are obtained and studied to the simulated turbulence. At the same time, new analyzing tools, orthogonal wavelet techniques, are applied to provide additional information in time domain. This makes it possible to study the intermittency event, one important characteristic associated with pressure peak activities in turbulence. Three parameters, scale energy, intermittency factor and intermittency energy are defined. Variation of these quantities as a result of different configuration is discussed. Finally, the corresponding variations in measured pressure peaks in relation with the variations of configuration as well as with the intermittency parameters are investigated. The work here is of important significance for future wind tunnel and field data comparison, and this could help to find the best simulation among all configurations.Master of Science
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LAI, RONG-YI, and 賴融毅. "Wind loads on parallel latticed frames." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/58808570056977217520.
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Huang, Hsin-Ta, and 黃新達. "Uncertainty Analysis of Along-wind and Across-wind Loads for Buildings." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/00529374312882756499.
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碩士國立台灣工業技術學院
營建工程技術研究所
85
This research presents a comparative study of current methods for calculation of along-wind and across-wind design wind loads. The methods considered are based on the codes of several countries and the results of wind tunnel tests (ANSI, 1982；SAA, 1989；NBCC, 1990；AIJ, 1996；R an, 1996；Islam, 1988) . The adopted wind loads are the along-wind load in Taiwan (1996) and the across-wind load in AIJ (Architectural Institute of Japan,1996). The combined scalar wind load effect is the maximum of the sum of the along-wind load process and across-wind load process, and can be approximated by a SRSS rule. Its probability distribution is derived by Monte Carlo simulations, considering alluncertainties. The obtained results will be the basis for evaluating the associated load factors and resistance factors.
49
Fu, Chung Lin, and 傅仲麟. "Wind Tunnel Investigations of Torsional Wind Loads Acting on Rectangular Prisms." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/42956006373303696659.
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碩士淡江大學
土木工程學系
85
Due to slenderness and less rigidity of modern building, wind loads become the dominate lateral force for highrise building design . The fluctuating wind loads acting on hig-rise building consist of drag force , periodic acrosswind force due to vortex shedding and torsional force due to load asymmetry. The paper studies torsional force on a rectangular prism with various cross sectional length -to-width ratio in two simulated atmospheric boundary layer flows .The experiments were performed by a new pressure-measured system. Through this system ,pressures at four side of rectangular prisms can be measured simultaneously, and then relationship between torsion and drag force ,lift force can be obtained. The results indicate that torsion will increase with length -to- width ratio .when length - to-width ratio less then critical value , 70%~90% of torque comes from asymmetries pressure distributions on the leeward side . If length -to-width ratio greater then critical value ,50%~90% of torque comes from the side face ,,the contributions increase with length -to-width ratio. The contributions to the torque from the two half forces of each side are opposite to each other and tend to cancel out .Therefore , the vortex shedding peak in the pressure spectrum on side face doesn''t appear in the torque spectrum .However , the contributions to the torque from the two leeward half faces are the same , the effects tend to add up .So the vortex shedding peak will appear in the torque spectrum .
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Baskaran, Appupillai. "Wind loads on flat roofs with parapets." Thesis, 1986. http://spectrum.library.concordia.ca/5556/1/ML30609.pdf.
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