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Abstract
The full-scale test building at Texas Tech University represents one of the best instrumented full-scale installations for determining wind loads on low buildings. In particular, it is intended to provide data of the highest quality for comparison with and verification of model scale experiments. In advance of full-scale data from the test building, a model scale experiment was undertaken to define the characteristics of the local pressures, partly to aid in the definition of the full-scale experiment and partly to provide an “unbiased” set of pressures for comparison. This paper describes the model and documents the test procedures in which results were determined for two simulated terrain roughnesses. Representative wind tunnel results are presented, and some comparisons are included with the first reliable data available from the full-scale experiment.
... Both model configurations previously described have the following full-scale dimensions: a length L of 13.72 m, a width B of 9.14 m, an eave height H of 3.96 m, and a roof slope of ¼:12 (1.2 • ). Note that the prototype dimensions and the roof slope are identical to the Texas Tech University (TTU) Wind Engineering Research Field Laboratory (WERFL) building [38]. The base and all four side walls of the model were constructed using regular plywood and lumber. ...
... The objective of the PTS methodology is to compensate for the missing low-frequency part of the turbulence spectrum by applying a post-test analytical correction to the large-scale model wind tunnel pressure results to better estimate the peak wind loads. Further details on the probabilistic approach behind the application of the PTS are provided in Mooneghi et al. [40] and Moravej [41], along with verification studies at various geometrical scales to estimate peak pressures on the Silsoe cube [43]and the TTU building [38]. The large-scale models based peak pressures were in good agreement with their fullscale counterparts (field data). ...
... This section compares the large-scale model (1:10) results conducted at the WOW for the bare deck configuration with full-scale pressure data on the TTU building [38] along with previous works on a 1:100 model [11] and another 1:10 model [51] of the same building. One edge tap (tap # 2) was selected for comparison between all four results (Fig. 4). ...
Standing seam metal roofs are one of the most commonly used types of roofs especially because of their additional durability and ease of construction. The performance of such roofs under extreme wind events like hurricanes depends on their structural strength and aerodynamic characteristics. Large-scale experimental testing was performed at the NHERI Wall of Wind Experimental Facility (WOW EF) using a 1:10 scale model of a gable roof building with double-lok trapezoidal seam roof panels along with eave and rake (gable) attachments. The results showed that the geometric features considerably modify the aerodynamic roof pressures. The standing seams along with both types of attachments reduced the peak suction at roof corners as compared to a bare surface roof by as much as 70% and 45% on an individual tap and area-average basis, respectively. In addition, mean uplift pressure reduction was observed. The power spectral densities of pressure fluctuations at most individual taps were also reduced with the addition of attachments. Also, the correlation between the pressures at different taps was significantly decreased in most cases, resulting in reduced area-averaged pressures due to the effects of the standing seams. However, as shown in a previous full-scale study, wind-induced vibrations can lead
to damage of such roofs and thus dynamic effects should be carefully considered for design purposes.
... Similarly, wind tunnel measurements come with high cost and expertise. Full-scale measurements for the determination of the wind-induced pressures have been previously performed in low-rise buildings with simple geometries [13][14][15]. Data deriving from full-scale measurements have been also used for the validation of reduced-scale measurements, such as wind-tunnel testing, and showed agreement that renders wind-tunnel tests an invaluable tool for the determination of wind pressure coefficients [13][14][15]. Numerical analysis by means of computational fluid dynamics (CFD) simulations is usually employed for the determination of wind loads in cases of complicated structures, such as high-rise buildings and non-conventional architectural structures [16]. ...
... Full-scale measurements for the determination of the wind-induced pressures have been previously performed in low-rise buildings with simple geometries [13][14][15]. Data deriving from full-scale measurements have been also used for the validation of reduced-scale measurements, such as wind-tunnel testing, and showed agreement that renders wind-tunnel tests an invaluable tool for the determination of wind pressure coefficients [13][14][15]. Numerical analysis by means of computational fluid dynamics (CFD) simulations is usually employed for the determination of wind loads in cases of complicated structures, such as high-rise buildings and non-conventional architectural structures [16]. CFD simulations are considered complementary to the traditional means of full-and reduced-scale measurements and require proper knowledge and expertise in order to achieve high quality and reliability [17]. ...
Wind pressure coefficients (Cp) are important values for building engineering applications, such as calculation of wind loads or wind-induced air infiltration and especially for tall buildings that are more susceptible to wind forces. Wind pressure coefficients are influenced by a plethora of parameters, such as building geometry, position on the façade, exposure or sheltering degree, and wind direction. On-site measurements have been performed on a twin medium-rise building complex. Differential pressure measurements have been employed in order to determine the wind pressure coefficients at various positions along the windward façades of the twin buildings. The measurements show that one building provides substantial wind shelter to its twin and the microclimatic effect is captured by the measured wind pressure coefficients. They also showed that the wind pressure coefficients vary significantly spatially along the windward façades of the medium-rise buildings. Furthermore, the pressure measurements showed that the wind pressure coefficients fluctuate significantly during the measuring period. The use of the fluctuating Cp values by means of probability distribution function (pdf) for the calculation of air infiltration has been evaluated. The results indicate that the air flows deriving using fluctuating Cp values are more accurate than the ones calculated by the conventional method of using mean Cp values.
... Two early studies of the TTU building should be noted. Surry (1989) reported on wind-tunnel studies performed at UWO prior to any full-scale data being available and Okada and Ha (1991) presented data collected at the Building Research Institute in Japan. ...
... The data reported by Surry (1989) were collected "in advance of the full scale data" so as to "partly provide an 'unbiased' set of pressures for comparison". Surry's motivation for this procedure was to avoid the subtle, but real, observation that "model experiments are often a matching process, where wind-tunnel simulations are varied until reasonable agreement is obtained, rather than being truly independent simulations". ...
... at Texas Tech University (TTU) (Levitan and Mehta, 1992a,b), huge amount of high quality data on vsind and building surface pressures has been collected, validated, and made available to researchers in the early 1990s. Since then, extensive wind tunnel simulations have been carried out all over the world (Surry 1991, Cochran and Cermak 1992, Okada and Ha 1992, Tieleman 1996, Cheung et al. 1997, Ham 1998, Ham and Bienkiewicz 1998, Bienkiewicz 1999. These full-scale/modelscale comparison and verification studies significantly improved our understanding of wind turbulence effect and wind tunnel simulation techniques. ...
... In comparing the wind tunnel test results with TTU fiill-scale data (Levitan et al. 1991), Surry (1991) noticed the significant differences in the peak pressure coefficients for oblique wind. He attributed this mismatch to the difference of gust stmctures, or specifically turbulence intensities and spectra between fiill-scale and model-scale approaching winds. ...
... The past wind tunnel experiments, such as those from the Boundary Layer Wind Tunnel Laboratory (BLWTL) at the University of West Ontario (UWO) 6 and the wind tunnel at Texas Tech University (TTU), 7 tested the wind pressures on the gable-roof lowrise buildings with different heights, horizontal dimensions, and roof slopes from different wind directions, at a length scale of 1:200, 1:100, and 1:50. Also, the full-scale measurement, [8][9][10] along with the in situ data collection during Hurricane Ivan 11,12 and Typhoon Mujigae and Sarika, 13 contributed to the understanding of the wind effects on the low-rise buildings. ...
Residential buildings in coastal communities are often elevated to mitigate flooding and wave-surge impacts. However, the elevations change the local wind field characteristics and may increase the aerodynamic pressure on buildings. Post-event reconnaissance showed that elevated buildings experienced severe structural damage to the roofs, walls, and floors during major hurricanes. Currently, our understanding of aerodynamic pressure on elevated houses is limited. In this paper, a large eddy simulation (LES)-based method is developed to better understand the wind effects on elevated buildings. The inflow generation method, discretizing and synthesizing random flow generation, is adopted to generate inflow boundary conditions satisfying the target spectrum. Two sub-grid scale models, the Smagorinsky and wall-adapted local eddy-viscosity models, are employed to represent the unresolved small-scale eddies. It is found that the eddy structure sizes can strongly affect the pressure fluctuations at the eddy separation zones. The present study advances the understanding of aerodynamics on elevated buildings and provides a reference for future LES-based research on wind effect modeling.
... Levitan et al. [48][49][50] conducted long-term on-site measurements of its wind load (wind press) and the wind field characteristics around the building, accumulating a large amount of measured data. The data has been repeatedly cited by scholars [51][52][53][54] to study the simulation of atmospheric boundary layer wind fields (including the incoming flow characteristics, wind environment, etc.), the pressure measurement techniques and wind pressure distribution on building surfaces. Therefore, this article further employs TTU data to verify the accuracy of the turbulence model (S-A-IDDES method) in calculating wind loads on low-rise buildings. ...
... The last eddy created by flow separation above the roof is closest to the building and produces a more significant wind suction force on the roof. [35], the field-measured data from TTU (Real) [36] and the wind tunnel experimental data from the University of Western Ontario, Canada (WT-UWO) [37], respectively. Clearly, the average and peak wind pressure coefficients obtained in this section of LES differ slightly from the wind tunnel experimental results, and the pulsation pressure coefficient is marginally smaller on the windward side. ...
Large-span open prefabricated spatial grid structures are characterized by light mass, high flexibility, low self-oscillation frequency, and low damping, resulting in wind-sensitive structures. Meanwhile, their height tends to be relatively low, located in the wind field with a large wind speed gradient and high turbulence area. Therefore, surface airflow is complex, and many flow separations, reattachment, eddy shedding, and other phenomena occur, causing damage to local areas. This paper took the Evergrande Stadium in Guiyang, China, as the research object and used the random number cyclic pre-simulation method to study its surface extreme wind pressure. Firstly, five conventional distributions (Gaussian, Weibull, three-parameter gamma, generalized extreme value, and lognormal distribution) were fitted to the wind pressure probability densities at different measurement points on the surface of the open stadium. It is found that the same distribution could not be chosen to describe the probability density distribution of wind pressure at all measurement points. Hence, based on the simulation results, the Gaussian and non-Gaussian regions of this structure were divided to determine where to apply which distribution. Additionally, the accuracy of the peak factor, improved peak factor, and modified Hermite moment model method were compared to check their applicability. Finally, the effect of roughness on the extreme wind pressure distribution on the open stadium surface was also investigated according to the highest accuracy method above. The findings of this study will provide a reference for engineers in designing large-span open stadiums for wind resistance to minimize the occurrence of wind damage.
... Compared to dominant positive feature contributions at pressure tap e12, extreme negative pressure (C p,min ) at the pressure tap (g7) at the corner of the roof was shaped by both positive and negative feature contributions (Fig. 15). Its base value C p,min = − 1.148 indicates intense suction pressure often detected at the corners of flat roofs (Surry, 1991;Sarkar et al., 1997;Wu et al., 2001). The features x/H, θ, and z/H further increased C p,min of Case 1 with θ = 22.5 • and C A = 0.3, while C A and y/H reduced its magnitude ( Fig. 15(a)). ...
This study used explainable machine learning (XML), a new branch of Machine Learning (ML), to elucidate how ML models make predictions. Three tree-based regression models, Decision Tree (DT), Random Forest (RF), and Extreme Gradient Boost (XGB), were used to predict the normalized mean (C p,mean), fluctuating (C p,rms), minimum (C p,min), and maximum (C p,max) external wind pressure coefficients of a low-rise building with fixed dimensions in urban-like settings for several wind incidence angles. Two types of XML were used-first, an intrinsic explainable method, which relies on the DT structure to explain the inner workings of the model, and second, SHAP (SHapley Additive exPlanations), a post-hoc explanation technique used particularly for the structurally complex XGB. The intrinsic explainable method proved incapable of explaining the deep tree structure of the DT, but SHAP provided valuable insights by revealing various degrees of positive and negative contributions of certain geometric parameters, the wind incidence angle, and the density of buildings that surround a low-rise building. SHAP also illustrated the relationships between the above factors and wind pressure, and its explanations were in line with what is generally accepted in wind engineering, thus confirming the causality of the ML model's predictions.
... In the two decades since its operation, the WEFRL has produced huge amounts of wind pressure data. Taking these data as benchmark, researchers around the world have conducted several comparative studies of wind tunnel tests and field measurements (Cheung et al., 1997;Endo et al., 2006;Hagos et al., 2014;Okada and Ha, 1992;Surry, 1991;Tieleman, 1996;Xu, 1995). Overall, the agreement between the model-scale and full-scale measurements is generally good for the mean pressure coefficients. ...
A full-scale experimental low-rise building with gable roof was constructed in a typhoon-prone area in China, aiming to study the wind effects on a typical low-rise building during tropical cyclones. Meanwhile, it was also intended to provide reliable full-scale measurements for verification of widely used simulation techniques, such as wind tunnel testing and numerical simulation. This paper presents a detailed comparative study of the wind effects on the experimental building between the full-scale measurements during six tropical cyclones and the wind tunnel test results on a 1:50 scaled model of the low-rise building, including point pressure coefficients, area-averaged pressure coefficients and wind pressure probability density functions. The model-scale and full-scale mean pressure coefficients exhibits a good agreement. However, significant differences are found for the root-mean-square (RMS) and peak negative pressure coefficients on the gable end roof under oblique winds. The probable causes for these discrepancies including inadequacy of large-scale turbulence, mismatch of Reynolds number and elevation angles (vertical wind angle of attack) in the wind tunnel test are explored based on the field measurements.
... C p values can derive from different sources, such as full-scale measurements, reducedscale measurements in wind tunnels, CFD simulations, databases and analytical models (Costola et al., 2009). Studies have shown that the most accurate way to define the C p values of a building are full-scale measurements, while wind-tunnel measurements and CFD simulations are following in accuracy (Costola et al., 2009;Costola & Alucci, 2007;Miyoshi, Ida, & Miura, 1971;Richards, Hoxey, & Short, 2001;Surry, 1991;Uematsu & Isyumov, 1999). Full-scale measurements are complicated, time-consuming, expensive and therefore rarely performed (Costola et al., 2009). ...
Wind pressure coefficients (Cp) are important for the correct calculation of the air infiltration of a building. Cp depends on wind direction, position on the building façade and site exposure, and is therefore influenced by the microclimate. The external coupling between building energy simulation (BES) software and computational fluid dynamics (CFD) pre-processing allows calculating building-specific wind pressure coefficients that can account for the microclimate. BESs have been performed in order to calculate the infiltration rate of a reference building using surface-averaged Cp values from two different sources; a standard database and CFD simulations from OpenFOAM. Tracer gas measurements were performed in the reference building in order to validate the simulation results. The results show the coupled CFD/BES method gives building-specific Cp values that represent adequately the microclimatic conditions, leading up to 45% more accurate air infiltration rates compared to conventional methods.
... Wind tunnel experiments are widely employed in mechanical engineering (Sakamoto and Haniu 1990), civil engineering (Meroney et al. 1996), and environmental studies (Jenkins et al. 1996). Wind flows around the aircrafts, buildings, and cars were frequently investigated in the engineering applications (Baals and Corliss 1981;Amitay et al. 2001;Surry 1991;Suzuki et al. 2003). In addition, numerous studies on air pollution and meteorology applications were conducted in wind tunnels (Baker and Hargreaves 2001). ...
Development and trend of global wind tunnel research from 1991 to 2014 were evaluated by bibliometric analysis. Based on the statistical data from Science Citation Index Expanded from Web of Science, publication performance of wind tunnel research was analyzed from various aspects, including publication output, category distributions, journals, countries, institutions, leading articles, and words analysis. The results show that scientific articles associated with wind tunnel increased dramatically, with Journal of Wind Engineering and Industrial Aerodynamics as the most productive journal. The USA has been leading in publication output since 1991, while China has become a new-rising force of wind tunnel research. NASA was the dominant institution in wind tunnel field which published most single institution articles and nationally and internationally collaborative articles. The citation lifecycles of the leading articles exhibited different patterns of their trends, but all reached a plateau in certain years. Based on synthesized analysis of title words, abstract words, author keywords, and KeyWords Plus, computational fluid dynamic (CFD) was found to be a hot issue, which needs experimental validation by wind tunnels. Wind loads and wind turbine also caused increasing attentions while lepidoptera and sex pheromone were less studied. In the wind tunnel articles, numerical simulation of CFD was increasingly mentioned while field measurement showed minor change, suggesting the rapid developments of CFD.
... The latter includes atmospheric boundary layer wind tunnel testing (e.g. Penwarden and Wise 1975;Cook 1975;Isyumov and Davenport 1975;Wiren 1975;Castro and Robins 1977;Robins and Castro 1977a,b;Tieleman et al. 1978;Isyumov 1978;Murakami et al. 1979;Britter and Hunt 1979;Beranek and van Koten 1979a,b;Irwin 1981;Huber and Snyder 1982;Stathopoulos 1984;Simiu and Scanlan 1986;Stathopoulos and Storms 1986;Schatzmann et al. 1987;Kawamura et al. 1988;Livesey et al. 1990;Surry 1991;Richards and Hoxey 1992;Kato et al. 1992;Lam 1992;Uematsu et al. 1992;Niemann 1993;Stathopoulos 1994, 1997;Visser and Cleijne 1994;To and Lam 1995;Sasaki et al. 1997;Meroney et al. 1999;Blocken et al. 2008a;Salizzoni et al. 2009;Tsang et al. 2012;Conan et al. 2012;Tominaga andBlocken 2015, 2016;Ricci et al. 2017a), water channel measurements (e.g. Princevac 2010;Pournazeri et al. 2012;Cruz-Salas et al. 2014;Neophytou et al. 2014;Karra et al. 2017) or water tank experiments (e.g. ...
Large Eddy Simulation (LES) undeniably has the potential to provide more accurate and more reliable results than simulations based on the Reynolds-averaged Navier-Stokes (RANS) approach. However, LES entails a higher simulation complexity and a much higher computational cost. In spite of some claims made in the past decades that LES would render RANS obsolete, RANS remains widely used in both research and engineering practice. This paper attempts to answer the questions why this is the case and whether this is justified, from the viewpoint of building simulation, both for outdoor and indoor applications. First, the governing equations and a brief overview of the history of LES and RANS are presented. Next, relevant highlights from some previous position papers on LES versus RANS are provided. Given their importance, the availability or unavailability of best practice guidelines is outlined. Subsequently, why RANS is still frequently used and whether this is justified or not is illustrated by examples for five application areas in building simulation: pedestrian-level wind comfort, near-field pollutant dispersion, urban thermal environment, natural ventilation of buildings and indoor airflow. It is shown that the answers vary depending on the application area but also depending on other—less obvious—parameters such as the building configuration under study. Finally, a discussion and conclusions including perspectives on the future of LES and RANS in building simulation are provided.
... In the comparison with full-scale results, wind tunnel experiments may correctly be seen as a matching process in which the simulations might just be varied until an acceptable agreement is achieved instead of being independent studies [25]. The bid to defy this was the motivation behind the work of Surry [60]; [59] who gathered wind tunnel data on the model of the Texas Tech building in advance of the full-scale studies. He found very good agreement between the two experiments particularly when the approaching wind was nearly normal to the ridge and the differing frequency responses in the measuring instruments have been accounted for on the magnitudes of the peaks. ...
Building codes such as the Eurocode have usually been used as a cheaper alternative to wind tunnel studies in the consideration of wind loading on a structure. It is often the case that very tall buildings and large structures have enough economic justification for expensive wind tunnel studies in their design stage. Such wind tunnel studies, as per state-of-the-art, feature simultaneous scanning of and acquisition of loading data from hundreds of pressure tappings with subsequent high-speed computer data processing and analysis. This is not the case for low-rise buildings which do not find their way into the wind tunnel except in the case where they are unusual edifices. Low-rise buildings, however, are the most damaged in wind storms. In addition, in the present times, their shapes are increasingly losing touch with the traditional and generic forms dealt with in the Eurocode. Therefore, the question is: How well does the Eurocode, which was put together with information from wind tunnel studies performed in the 50s and 70s using currently outdated data acquisition techniques, deal with present building shapes? The study was based on models of a simple cuboidal building; a quasi-rectangular building with inset faces in its plan; and a building plan featuring a re-entrant corner possessing curved surfaces at the internal and external junctions of its wings. It was concluded from the results of the study that adapting the Eurocode wind loading provisions to irregular building plans characteristic of modern times gives very unsafe solutions. The variations of pressure with wind direction on the internal walls of the wings of and the curved surface at the internal junction of the re-entrant corner were observed to follow coherent wave forms which are mutually similar. These call for further research.
... Wind tunnel is a tool commonly used in aerodynamic research (Stathopoulos 1984). In wind tunnel experiments, effects of air flow were investigated on solid object, such as planes (Amitay et al. 2001), building (Surry 1991), cars (Suzuki et al. 2003), and birds (Kvist et al. 2001). They can simulate turbulent characteristics, wind conditions, and pollutant dispersion at a scale-down condition (Cook 1978). ...
Wind tunnels have been widely employed in aerodynamic research. To characterize the high impact research, a bibliometric analysis was conducted on highly cited articles related to wind tunnel based on the Science Citation Index Expanded (SCI-EXPANDED) database from 1900 to 2014. Articles with at least 100 citations from the Web of Science Core Collection were selected and analyzed in terms of publication years, authors, institutions, countries/territories, journals, Web of Science categories, and citation life cycles. The results show that a total of 77 highly cited articles in 37 journals were published between 1959 and 2008. Journal of Fluid Mechanics published the most of highly cited articles. The USA was the most productive country and most frequent partner of internationally collaboration. The prolific institutions were mainly located in the USA and UK. The authors who were both first author and corresponding author published 88% of the articles. The Y index was also deployed to evaluate the publication characteristics of authors. Moreover, the articles with high citations in both history and the latest year with their citation life cycles were examined to provide insights for high impact research. The highly cited articles were almost earliest wind tunnel experimental data and reports on their own research specialty, and thus attracted high citations. It was revealed that classic works of wind tunnel research was frequently occurred in 1990s but much less in 2000s, probably due to the development of numerical models of computational fluid dynamic (CFD) in recent decades.
... In addition, their study found that the pressures on the full span trusses of the gable roof can be approximately twice those of the full span hip roof trusses at the same wind speed. Previous studies and research (Holmes, 1979;Uematsu et al., 1999;Stathopoulos et al., 1979;Vickery, 1986Vickery, , 1991Vickery, , 1992Vickery, , 1994Surry, 1991;Scruton, 1971;Kopp et al., 2008;Tieleman, et al., 1996;Ginger, 1997;McKinnon,2003; etc.) clearly show that the proper evaluation of internal and external pressure is important for calculating the wind load on the house, otherwise it will initiate damage on the vulnerable part of house structures (connections, roof, wall, ceiling, etc.). ...
Windstorms are one of the major causes of severe damage to houses and other infrastructure. Damage investigations indicate that the roof is the most vulnerable part of a timber-framed house, and that failures take place at inter component connections; hence there is a need to study the load sharing and structural response of these timber-framed house structural systems to assess their performance. Contemporary houses in many parts of Australia are brick veneer structures with metal or tile clad roofs that are built to National Construction Code of Australia's design specifications.
Full-scale tests were carried out on a representative part of a brick veneer contemporary house to assess the loading effects on roof to wall connections and load sharing. Tests were conducted for each stage of construction: bare frame followed by the installation of roof battens and cladding, wall lining, ceiling, etc. These construction stages were used to assess the contribution of the structural and lining (i.e. ceiling, ceiling cornice and wall lining) elements to the load sharing and response of the timber-framed house structure to wind loading. Results show that the vertical load sharing of the timber-framed house through the roof to wall connection depends on the stiffness of the roof to wall connection and the truss location (i.e. whether located at the end or middle). The contribution of the lining elements to the vertical load sharing is about 15% to 20%.
In addition, individual component tests were conducted on the roof to wall framing anchor (i.e. triple grip and truss grip) connections to examine their structural response to loading. This study also showed that construction defects in roof to wall connections influence the design uplift capacity. Two missing nails out of ten in the hand nailed triple grip connection (i.e. one nail from the truss and other one from the top plate) reduces the design uplift capacity by about 40 % of the "Ideal" hand nailed triple grip connection. Finite element models were also developed for part of the timber framed house and roof to wall connections (i.e. triple grip and truss grip connections) using ABAQUS finite element software. Results obtained from the finite element models were compared with the experimental tests, showing good agreement. This finite element model can be used to predict the roof to wall connection response and truss hold-down force variation with a range of construction defects and truss bay configurations. The overall outcomes can be used to evaluate house structure vulnerability to wind loading, and to improve the design and standards of timber-framed houses.
... There is a discrepancy between the measured and Von Karman spectra, primarily due to the large length scale selected, which is indicative of a mismatch of the longitudinal turbulence scale by about a factor of 2 based on the shift in the high-frequency region of spectra (the turbulence integral length scale can be obtained using PSD). The mismatch in the power spectral densities could lead to the difference between simulated and full-scale fluctuating pressures (Asghari , 2015Surry, 1991). However, this level of mismatch is likely to be inconsequential for point pressures and averages over small areas where the pressure patterns are primarily dominated by mean roof height and configurations of edges (Ho et al., 2005). ...
A series of wind tunnel tests were conducted to investigate the effects of parapets of different configurations and various heights on the wind loading of a flat-roofed low-rise building. Local wind pressures, area-averaged peak pressures, and overall roof uplift force on the roof were determined. Spectral analysis was also performed to better understand the mechanism of how the presence of parapets affects the wind effects on the building. Additional attention was given to the power spectral density and non-Gaussian features of the area-averaged wind pressures. The results show that low parapets (h/H no more than 0.1) often increase suctions in the roof corner region. The presence of high parapets results in a decrease in the wind effects over the roof corners; however, it also leads to a growth of the uplift force over the entire roof. Comparisons among many different parapet configurations show that the ones with the raised and bottom-slotted corners help to efficiently alleviate the worst suction on flat roofs. In addition, the high parapet acts as a low-pass filter, filters out parts of the high-frequency energy in the approach flow, and stabilizes the wind pressure distribution on roof.
... The effect of large-scale, low frequency turbulence is somewhat like the effect of changes in mean wind speed and direction. Comparison between full-scale and wind tunnel data on Texas Tech University (TTU) test building [7][8][9][10] and Silsoe Cube [4] showed good agreement between the laboratory and field data for mean pressures. However, the agreement for the peak and RMS point pressures was found to be less satisfactory at critical locations in the roof corner region. ...
This paper presents a wind tunnel method called partial turbulence simulation (PTS) for predicting peak wind loads on low-rise buildings and small structures. For these small structures the typical model scales (1:10 to 1:100) are necessarily larger than for large structures such as tall buildings and stadiums (1:200 to 1:600). The larger model scales are needed so as to avoid adverse Reynolds number effects, maintain geometric accuracy and attain the desired level of resolution of pressure measurements. However, with larger model scales there are challenges in simulating the full turbulence spectrum of the natural wind. Due to the limited dimensions of most wind tunnels it becomes impossible to simulate the large turbulence eddies, corresponding to the low frequency end of the spectrum. If the approach is taken of trying to match the overall turbulence intensity, the high frequency part of the spectrum has too high a value, which is undesirable because this part of the spectrum can have a dominant effect on the behavior of shear layers and separation zones on the structure. In the PTS method, the wind tunnel tests focus on achieving a good match of the high frequency part of power spectrum. The effects of the missing low frequency turbulence (including the longitudinal, lateral and vertical components) are then included in post-test analysis using the quasi-steady approximation. The paper describes the theoretical background to the PTS method and how to determine appropriate turbulence intensity for the model tests. To include the effects of lateral and vertical turbulence, a number of tests are required over a range of wind azimuth and pitch angles in small angle increments. To assess the accuracy of the assumptions and analysis method, pressures on large-scale models of the Silsoe cube and Texas Tech University research buildings were measured in Wall of Wind facility at Florida International University with partial flow simulation. The predicted full-scale pressures from the theory were compared with the pressures measured on the respective prototypes in flow with full turbulence spectrum. Results showed an encouraging level of agreement. Wind tunnel testing is a well-established practice to determine wind loads on buildings and structures. For tall buildings the model scales used are typically in the range of 1:300 to 1:600. However, for small structures and building appurtenances much larger model scales are needed than for large structures, so as to maintain modeling accuracy and minimize Reynolds number effects. Ideally wind tunnel flows should have properties (mean wind profile, turbulence intensity, turbulence spectrum, and integral length scale) similar to those of atmospheric boundary layer (ABL) flows. However, when the model scale is large, the ability to obtain a large enough turbulence integral scale in the wind tunnel is usually compromised by the limited dimensions of the wind tunnel. This means that in normal boundary layer wind tunnels it is not possible to simulate the low frequency end of the turbulence spectrum when using the larger model scales needed for small structures. As a result, many of the model tests on these structures have been performed with less than ideal simulation of the turbulence spectrum [1]. This can affect the local flows over the building surfaces where the turbulence interacts in important ways with shear layers coming off the wall corners and roof edges. A number of studies [2-5] have shown that that accurate simulation of high frequency turbulence is necessary for correctly modeling flow separation and reattachment. Irwin [6] found that for some studies it is reasonable to match the turbulence spectrum only at high frequencies. This approach is called " Partial Turbulence Simulation (PTS) ". The effect of large-scale, low frequency turbulence is somewhat like the effect of changes in mean wind speed and direction. Comparison between full-scale and wind tunnel data on Texas Tech University (TTU) test building [7-10] and Silsoe Cube [4] showed good agreement between the laboratory and field data for mean pressures. However, the agreement for the peak and RMS point pressures was found to be less satisfactory at critical locations in the roof corner region. One of the reasons of this discrepancy was attributed to the mismatch of the turbulence spectrum in the laboratory flows. Reynolds number effects may also be part of the reason. Recent experiments at high Reynolds number and comparisons between full-scale and model-scale experiments have indicated
... While several previous studies reported pressure coefficients for roofs of various slopes with different wind direction angles [1][2][3][4][5][6][7][8][9][10][11]. In general they examined wind loads on the eaves of gabled roofs with small slopes or at roof edges or ridges. ...
This paper is experimentally investigated, and developed a numerical model for predicting, wind loads on roofs with various geometries. Using computational fluid dynamics simulation, several turbulence models were compared (k-ε, RNG, Grimaji, Baldwin-Lomax zero-equation, New k-ε, Shi-Zhu-Lumley). The Baldwin-Lomax turbulence model resulted in the most accurate results, and thus was adopted for further analyses. Pressure distributions on gabled roofs of different slopes (α=10°, α=20°, and α=30°) for various wind speeds and directions were measured in wind-tunnel experiments, and also predicted using the model. Comparing the values from the experiments to those estimated by the model revealed that the model sufficiently predicted both the local and average pressures formed on roofs for various wind velocities. There were, however, some minor discrepancies between measured and predicted pressure coefficients, mostly at roof corner points and back surfaces. The present work not only provides detailed information on wind load for roofs of specific geometries, but fills a void in current wind load standards and codes of practice, which lack sufficient data on middle regions of roofs with high slope angles. Moreover, the present study helps lay the foundation for eventually replacing expensive and time-consuming wind-tunnel tests with a model that accurately determines wind loads before roof production and installation, therefore minimizing potential roof damage and losses of life and property due to roof collapse. However, the model would benefit from further refinement and verification to improve its capability.
... Full scale studies required to understand more complex problems along with the need of validation requirements of numerically obtained data has its own role in engineering problems. Various full scale studies were also conducted with a view to produce standard documents and guidelines by Hoxey et al. and others [6][7][8][9][10][11].This paper demonstrates the application of powerful CFD to a simplest 2-D problem for calculation of pressure co-efficient on external surfaces subjected to wind flow. Widely speaking, Numerical modeling for CFD study using FEM/CVM/CV-FEM/ FDM based software/code has numerous parameters associated with it and these are complexly integrated and interdependent -which mainly governs the quality of output from it. ...
Extension of the effort to demonstrate application of Computational Fluid Dynamics (CFD) technique to obtain Pressure Coefficients on a single roof gabled like closed structure using ANSYS-Flotran module, proves a necessity to understand influence of various associated parameters. In pre-study kind of it, graphically obtained results are compared with data obtained from full-scale study as well with computational results published in literature to validate modeling methods and components. Collectively, computational results are absolutely sensitive to various parameters like meshing size & patterns, application of boundary conditions, turbulence models, domain size used to model flow environment like height of domain, upstream length L 1 (distance between inlet plane to windward face),downstream length L 2 (distance between leeward face to outlet plane). Using validated procedures and input parameters conducted before, parametric study is carried out to present the influence of geometrical parameters like fluid domain sizes on pressure coefficient prediction. At the end, concluding remarks derived, provide the important guidelines for fixing up the fluid domain size for 2-D simulation in ANSYS FLOTRAN.
... This plot shows the variation of the pressure in time. The computed mean pressures are in good agreement with field and wind tunnel measurements reported in Surry (1991) and Okada and Ha (1992). The peak pressures on the roof are close to the 1/65 wind tunnel model of Okada and Ha (1992). ...
Status and challenges in computing peak pressures around a building is identified. The one issue yet to be resolved is grid independent computation of flow around buildings. The importance of grid independence is illustrated by performing systematic grid refinement around a bridge section. The computed drag coefficient and Strouhal number for fine grid are in good comparison with wind tunnel measurements. Similar study is also reported for flow around a building. The computed mean and peak pressure coefficients as well as flow features for two grid systems are reported for comparison. The importance of inflow turbulence is also addressed.
... To assess the wind load in low-rise buildings most of the experimental investigations have been conducted without considering the effect of boundary wall. However, boundary wall is a very commonly used architectural feature with low-rise buildings in India as shown in Comparisons between full scale and wind tunnel model study have been made by Surry (1991), Okada and Ha (1992), Cochran (1992), Lin et al. (1995), Tieleman et al. (1996) and Endo (2006). Good agreement between the laboratory and field data has been found. ...
... Surry [33] did a wind tunnel experiment on the low-rise experimental building at Texas Tech. He did his experiment with a 1:100 scale model with two terrain roughnesses. ...
... They are very useful in determining wind loads on low buildings. These full-scale results have already been compared with some wind tunnel results measured at the University of Western Ontario [2]. ...
A full-scale 48-foot shipping container was instrumented with surface pressure taps and loaded onto a number of single- and double-stacked container freight trains. Surface pressure data enabled the container pressure drag coefficient to be evaluated for a range of different train loading configurations, container positions along the train, and atmospheric wind conditions. Field-based measurements show that for low and high crosswind conditions surface pressure distributions measured on the front face of the instrumented container are in good agreement with those reported in past studies. However, the magnitude of the pressure drag coefficient was found to be typically 50% lower for all loading cases analysed compared with previous seemingly analogous wind-tunnel and numerical investigations. For high crosswind conditions, the drag coefficient was found to increase and correlated well with the level of asymmetry observed in the measured pressure distributions. This was true for all cases regardless of the position along the length of the train. In the absence of direct information of the incident free-stream wind conditions, the level of asymmetry in the pressure distributions was found to provide a viable indirect method for assessing the impact that crosswinds have on the aerodynamic drag of freight trains.
This book grows out of a desire to understand, in building science terms, the environmental features of traditional building design practices on Yogyakarta Special Region (Indonesia). The construction of traditional dwellings conforms to a set of rules, determining both the form and process of construction.
The book describes tests of a number of factors related to traditional Javanese buildings for their effect on thermal comfort and air flow, isolating those design aspects and analysing them through contemporary techniques.
Having proposed a scientific rationale behind traditional customs, two building styles, Joglo and Limasan are analysed. These styles are shown to relate to traditional numerological systems (petungan; i.e. sri and kitri), which have governed the specific details of domestic construction, and to the scale and siting of structures within the designated traditional guidelines. For comparison, simple hip-roofed dwelling (not applying Javanese style, petungan, and materials), representing current practices, were modelled.
A commercial Computational Fluid Dynamics program was used as the principal research tool, testing thermal comfort through computer simulation.
The main conclusion reached by this book is that traditionally designed Javanese architecture is thermally comfortable in a hot humid climate, more so than the simple hip-roofed dwelling. Literature studies reveal that modern building science ideas on thermal comfort in hot humid climates had been applied instinctively in traditional Javanese architecture. Computer simulation confirms them as thermally comfortable.
Differences in style, petungan values, and scale were found to affect thermal comfort slightly, through their effects on the aerodynamic and thermal performance of the buildings. On the other hand, factors relating to materials have a significant effect on thermal comfort. The high porosity of traditional clay tile roof systems has provided Javanese buildings with a continuous ventilated roof, which is superior to corrugated steel from the point of view of ventilation of the dwellings.
In addition, CFD modelling has proved to be a valid means of testing airflow within and around buildings. However, calibration is needed to ensure the CFD program performs accurately and reliably. Simplification of data input is also recommended to minimise complication in the simulation without necessarily sacrificing the accuracy of the results. Further applications and current limitations of CFD technology are discussed.
A novel full-scale field test was undertaken to assess the aerodynamic performance of shipping containers loaded on inter-modal freight trains. The aerodynamic performance of an instrumented 48 ft container, located 185 m downstream of the locomotive, is assessed in the context of surface pressure, weather station, and GPS data sets. Previous studies on the aerodynamics of trains have been largely limited to low-resolution, reduced-order and scaled; field, numerical and wind-tunnel studies; respectively. The objective here was to determine the capacity of this novel field-based method to assess the aerodynamic performance of full-scale train containers for a large range of operating conditions. For low wind conditions, where the yaw angle is predicted to be low, measured surface pressure distributions on the front and base of the container are similar to that of past work however the magnitude of the drag coefficient was much lower, by up to 65%. This suggests that previous studies are yet to fully detail the drag profile of containers located at large downstream distance. Observed asymmetry of the pressure distribution on the front of the container are generally consistent with wind conditions measured at nearby weather stations and can be used as a proxy to determine the wind yaw angle at the train.
As high-rise structures are constantly emerging worldwide, wind effects on wind-sensitive structures are correspondingly getting increasing concerns, especially in tropic cyclone prone areas. This paper presents the analyzed results from field measurements of wind effects on a 600 m high skyscraper located in Shenzhen during a landfall typhoon. Field monitoring of wind-induced pressures on the skyscraper was conducted by a structural health monitoring system. The major objective of this study is to further understand typhoon-generated wind pressures on super-tall buildings. In addition, wind tunnel test of simultaneous pressure measurements on the building model was performed. Full-scale and wind tunnel measurements of wind-induced pressures on windward, leeward and side faces of the super-tall building were analyzed and compared. A whole range of characteristic properties, including pressure coefficient, probability distribution, peak factor, power spectral density, and correlation of cladding pressures were presented and discussed. The findings of this study are expected to be of interest and practical use to professional and researchers involved in the wind-resistant designs of super-tall buildings in tropic cyclone prone regions.
This paper presents an investigation of the uncertainties inherent in the South African formulation of design wind loads on structures, as stipulated by SANS 10160-3:2011. The investigation follows from the identification of anomalous values in the existing South African probabilistic wind load models during a reliability assessment of SANS 10160. The primary wind load components which have the greatest effect on the total wind load uncertainty are identified as the time variant free-field wind pressure, followed by the time invariant pressure coefficients and terrain roughness factors. A rational and transparent reliability framework for the quantification of the uncertainties inherent in the formulation of these components is then presented. Probabilistic models of these components were developed following independent investigations of each component. The results from these investigations show that the existing probabilistic wind load models underestimate the uncertainty of the wind load components, particularly when considering the time invariant components. © 2018 South African Institute of Civil Engineers. All rights reserved.
Knowledge of the pressure distributions on building surfaces is essential for a complete understanding of infiltration, wind-induced ventilation and wind loads. Earlier studies have shown the influence of different façade appurtenances like balconies on the wind-induced pressure on building facades. However, a detailed investigation of the impact of facade appurtenances on the pressure distribution on building facade has not yet been performed. This is especially the case for high-rise buildings. This paper, therefore, presents a detailed study on mean wind pressure distributions on the windward façade of a high-rise building with and without façade appurtenances at wind direction of 0°. The realizable k-ɛ turbulence model in 3D steady Reynolds-Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) is used for predicting. The evaluation is based on validation with wind-tunnel measurements. The results show that the presence of balconies can significantly influence the Cp distributions on the windward façade. This influence greatly depends on the size and geometry of balconies.
This research highlights the importance of Computational Fluid Dynamics (CFD) simulation software in optimizing building efficiency through studying natural ventilation for both thermal comfort and human health in residential buildings. Besides introducing methodologies used in this regard and ways of validating results such as wind tunnel and in-situ measurements, selecting the appropriate turbulence model and presenting best practices in performing simulation process. Youth housing in New Damietta has been selected as a case study to evaluate natural ventilation inside 3 different prototypes depending on the local weather station wind data. A wind tunnel validated K-epsilon turbulence model has been used for this simulation. The results of this research emphasizes the importance of using simulation software as a credible tools in achieving thermal comfort energy efficiency in residential buildings.
Full text available at the following link until October 5, 2016:
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An experimental investigation of surface static pressure distributions on hexagonal cylinder was conducted. The study was performed on both the single cylinder and the group consisting of two cylinders, one in the upstream and another in the downstream side. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.13 x 104 based on the face width of the cylinder across the flow direction in a uniform flow of velocity 13.2 m/s. The study was done on the single cylinder at various angles of attack from 00 to 500 at a step of 100. The surface pressure distributions were measured with the help of an inclined manometer. Then the group of two cylinders was taken into consideration for the study and the surface static pressures were measured for various inter- spacing of 1D, 2D, 3D, 4D, 6D and 8D, D being the width of the cylinder across the flow direction. In each case the wind velocity was kept constant at 13.2 m/s. The pressure coefficients were calculated from the measured values of the surface static pressure distributions on the cylinder. Then the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. It was observed that the drag coefficients become remarkably smaller compared to those for a sharp-edged square cylinder. It was also observed that at various angles of attack, the values of the lift coefficients were insignificant compared to those for a sharp-edged square cylinder. It can be further concluded that the hexagonal cylinder produces significantly low values of drag and lift forces and they approach to those of the cylinder with circular cross-section.
Pressure distributions created by wind flow on low slope roofs is an issue addressed by many wind tunnel studies and selective field experimental studies. Building codes and standards specify pressure coefficient data to determine the wind loads for commercial roofing claddings. Field measurements can provide valuable data to validate the current code provisions for wind loads, as well provide supporting data for existing wind uplift test methods for roof claddings. Thus the Special Interest Group on Dynamic Evaluation of Roofing Systems (SIGDERS) selected four locations (Ottawa, Vancouver, Mt. Pleasant and Rialto) across North America and collected wind speed, wind direction and wind pressure data for extended time periods to understand the wind interaction with low slope membrane roofs. This paper presents the data collected from November 2012 to November 2013 from the Ottawa, Ontario site.
Based on the National Building Code of Canada׳s (NBCC) zoning procedure, pressure taps were installed to obtain data for the corner, edge and field roof zones. Occurrences of wind speed exceeding 16 m s⁻¹ were considered for various wind directions. Peak and mean pressure coefficients were calculated and compared with NBCC (2010)’s specifications. When instantaneous peak pressure coefficients were compared with the NBCC (2010), the measured data exceeded NBCC (2010)’s specifications for some wind directions. Nevertheless, when the pressure coefficients were compared by paring with their respective tributary area, the data concluded that the current NBCC (2010)’s specifications for the roof cladding and components are equally adequate for the wind load design of low slope membrane roofs.
Data from full-scale building tests conducted in Texas Tech University are used to quantify the uncertainties associated with the use of computational fluid dynamics to obtain wind load predictions for full-scale structures. It is demonstrated that the effects of computational domain is relatively small, and the effects of grid arrangement, turbulence model and inlet boundary condition are relatively obvious. Finally, guidelines are suggested for reasonable design and suitable choice of turbulence model.
The results of wind-field full-scale measurements in civil engineering structures are the directest information to afford insight into wind load effects, dynamic response, and breakage on structures. Likewise, they are the most authoritative bases used for revising present test methods and theoretical models. The development of civil engineering structures, such as tall buildings, high-rise towers, long-span bridges, and long-span spatial structures with higher flexible and lower damping are briefly reviewed here. Wind-field full-scale measurements are attached importance to for design of wind resistant structures. Subsequently, developments in wind-field full-scale measurements and new measuring techniques are summarized. Especially, for the purpose of practical applications of wireless sensor network (WSN) in wind-field full-scale measurements, the key technical issues to be resolved are proposed.
In this study, we developed a data processing program for the wind on bridge based on C# programming language, Windows Presentation Foundation (WPF) framework and the idea and process used in analyzing and processing wind data. The program proposed functioned in data segmentation, processing of bad points and calculating of wind speed, wind direction, turbulence intensity, gust factor, integral scale and power spectral density. Moreover, it realized the rapid and automatic calculation of the wind characteristic parameters and convenient processing of the massive wind data observed.
Wind tunnel pressure measurements and numerical simulations based on the Reynolds Stress Model (RSM) are compared with full and model scale data in the flow area of impingement, separation and wake for 60° and 90° wind azimuth angles. The phase averaged fluctuating pressures simulated by the RSM model are combined with modelling of the small scale, random pressure field to produce the total, instantaneous pressures. Time averaged, rsm and peak pressure coefficients are consequently calculated. This numerical approach predicts slightly better the pressure field on the roof of the TTU (Texas Tech University) building when compared to the wind tunnel experimental results. However, it shows a deviation from both experimental data sets in the impingement and wake regions. The limitations of the RSM model in resolving the intermittent flow field associated with the comer vortex formation are discussed. Also, correlations between the largest roof suctions and the comer vortex "switching phenomena" are observed. It is inferred that the intermittency and short duration of this vortex switching might be related to both the wind tunnel and numerical simulation under-prediction of the peak roof suctions for oblique wind directions.
This study represents an experimental and computational investigation of the aerodynamic and heat transfer characteristics of two interfering low-rise buildings. The two buildings situated in line are similar with a slanted roof. The investigated parameters include the gap between the two buildings, the roof angle, and the wind speed (Reynolds number). The solar radiation absorbed by the roof and conducted into the building that appears as a cooling load is also studied. Heat flow through such roofs is found to be sensitive to number of factors, including, wind speed, roof angle and surface to air temperature difference. The experimental results demonstrated pressure distributions on the different walls and roofs of the two buildings. Also, the drag force on the two buildings is measured for different interfering cases. The corresponding numerical results were obtained using the computational finite element procedure (ANSYS 9.0 for two-dimensional model and Fluent 6.12 for three dimensional model) that uses the standard k-H model. Computational results include velocity vectors, distributions of turbulence kinetic energy, and temperature gradients as well as the pressure distribution. Certain consideration was paid to the difference in aerodynamic characteristics between a single building and two interfering buildings. Comparison between the numerical and experimental results showed a good agreement in terms of gross feature of mean flow for all cases examined, although some detailed differences were observed.
Owing to the increasing number of high-rise buildings and large glass facades and the resulting problem of safe and effective maintenance, many trials have taken place in the last few years to develop automated cleaning systems. So as to guide the robot's movement on the facade, this study proposes the built-in-guide type building maintenance robot system using additional module such as guidance mullion to the facade. In specific, this paper proposes robotic building facade cleaning system which is directly subjected to minimize human labor; that improves the process efficiency and economic feasibility. The sensor for detecting contamination of building's outer-wall glass is proposed; Kalman filter was used for estimating robots' status with the contamination of the window glass. Through the simulations, an effective way of task execution is introduced and the feasibility was verified with the proposed sensor based motion control algorithm.
With the increasing number of high-rise and large-scale buildings, modern buildings are becoming intelligent, and are incurring high construction costs and requiring careful maintenance. Maintenance works for high-rise buildings significantly depend on human labor, unlike other construction processes that are gradually being automated. The resulting accidents may produce very high social and economic losses. To address this problem, herein, this paper proposes robotic building maintenance system using multi-robot concept, in specific, cleaning a building façade which is directly subjected to minimize human labor; that improves the process efficiency and economic feasibility. The sensor for detecting contamination of building’s outer-wall glass is proposed; Kalman filter was used for estimating robots’ status with the contamination of the window glass. Task allocation of the sensor based multi-robots for an effective way of task execution is introduced and the feasibility was verified through the simulations.
Velocity and pressure fields around a low-rise experimental building located at Texas Tech University are predicted using Large Eddy Simulation ( LES ). The distributions of mean and rms surface pressure coefficients predicted by LES are compared with those of field and wind tunnel measurements. The results of LES correspond very well with the measured data.
An important research facility has been constructed at Texas Tech University to study wind effects on low buildings in the field. This laboratory features many capabilities not found in past field experiments, and presents tremendous new learning opportunities. The facility is being used to pursue research in wind loads on building surfaces, internal pressures, performance of roofing in wind environment, and ventilation and exhaust studies around the building. The paper includes sufficient detail on the test building and pressure measuring system to permit researchers in physical and analytical modeling to make appropriate comparisons with the field measured data.
A comparison of pressure coefficients and spectra for the curved eaves Silsoe Building at model and full scale is made following a comparison of the full-scale and 1:100 scale wind tunnel profile. The comparison is restricted to a wind direction normal to the building ridge and to a mid-building-length set of taps. The use of a floor-mounted static reference pressure resulted in better comparisons between full and model scales both of coefficients and particularly of frequency domain data. The frequency domain data on the windward wall mid-height tap show good agreement for full-scale frequencies from 0.001 to 1.0 Hz as does the freestream wind dynamic reference pressure.
This paper summarizes the major findings of an in-depth study [1] of wind pressures on the Aylesbury experimental house. The scope of the study includes part of the Aylesbury Collaborative Experiment (ACE), a detailed examination of the full scale pressure data, and various comparisons between model scale data; namely, between new 1:100 and 1:500 scale tests at UWO, between current and previous data obtained by the authors [2,3], and between the UWO 1:100 scale data and pressure data obtained from 1:100 scale model tests from three other wind tunnel laboratories.The results of the study indicate that much of the mean pressure data obtained at full scale are subject to reference static pressure errors, but the corresponding fluctuating pressures are reliable and agree well with model scale in most instances. The comparison of pressure data obtained from the different laboratories indicates that significant differences in the measured pressure data occur even though identical models are used.
An account is given of the measurement of wind pressures on a two-storey housing estate on the outskirts of Aylesbury, 65 km north-west of London. The estate immediately adjoins an open country fetch extending uninterruptedly for about 15 km to the southwest. The site and installation are described, including the variable geometry building erected on open ground adjoining the estate. Wind pressures were recorded at a total of 44 positions on seven houses in the estate, and at 72 positions on the experimental building, transducers being mounted on both walls and roofs. Load cells were also installed in the experimental building to record separately total overall loads and total roof loads. Measurements of velocity were made using cup anemometers mounted at 3 m, 5 m, and 10 m, on a fixed mast, suitably sited in the vicinity of the experimental building. In addition, anemometers mounted on a 20 m portable mast were used to investigate the upstream velocity profiles, and also the flow patterns within the urban area. The experimental building housed all the recording equipment which comprised multichannel FM magnetic tape recorders. Records were taken in analogue form and were subsequently digitised in order to calculate mean, rms and extreme values, probability distributions, autocorrelations, power spectra and cross-correlations. Measurements have been made for a variety of wind speeds and directions, and also for several roof pitches on the experimental building between 5° and 45°. Preliminary results are presented and discussed.
Research into wind loads on low buildings continues to absorb a significant effort at the Boundary Layer Wind Tunnel Laboratory at The University of Western Ontario. This paper presents an overview and some key results from a number of different studies taking place in parallel to those being reported in other papers at this conference. These studies include: 1.1. The comparative wind resistance of hip and gable roofs, carried out primarily by D. Meecham under the guidance of A.G. Davenport and the author;2.2. A novel technique utilizing simple models that fail under wind loading that is being used to investigate overall building performance, developed through a number of student projects;3.3. The reduction of wind loading requirements for regions remote from edges of very large low buildings, carried out with E.M.F. Stopar;4.4. The characteristics of pressures very close to edges, carried out by J.R. Lankin in cooperation with Dr. T. Stathopoulos;5.5. The characteristics of pressures on a model of Kishor Mehta's full scale test building at Texas Tech carried out by E.M.F. Stopar.The first and third topics are essentially complete (Meecham, 1988; Surry and Stopar, 1989); the work to date on the second topic has been submitted for publication (Surry, Meecham, Stopar and Cholod, 1988), but is still an ongoing research topic, as are the last three items.In all cases, this paper will briefly present the main ideas behind the research and the key findings.
Some inconsistencies have been noted between the suction data published by different authors for flat rooftops of low-rise buildings. New experimental data, together with some of the earlier data, show that the worst suctions are only mildly sensitive to the characteristics of the approach-flow boundary layer and that with low parapets the true worst suctions occur very close to the edges of the roof. It is hypothesised that the true worst suctions were missed by some of the previous investigators due to a lack or scarcity of pressure taps sufficiently close to the roof edges of their model buildings. The region of worst suctions comprises only a very small fraction of the total roof area and its influence on structural loads is small; it is, however, important as regards wind damage to roof-cladding systems. The paper includes data for the high-suction region of flat rooftops on low-rise buildings in 45° oblique winds for a range of parapet heights.
Most low buildings are sutuated in urban areas in the midst of neighbouring buildings, trees, fences, billboards and parks. These cluttered, undisciplined surroundings can have as much effect on the wind loads as do the details of the geometry of the building itself and often even more so.Studies in recent years have focussed primarily on the influence of turbulent boundary layer winds in open terrain relatively free of surrounding obstructions in which building geometry is a dominant factor. In this study, a new approach is proposed to study the interference of local obstructions on low building wind loads from a statistical point of view through wind tunnel experiments. An experimental wind tunnel simulation with randomized wind load parameters, especially random surroundings, is proposed. The generated data base, together with data from other relevant studies, can form the basis for a reliability analysis to predict wind loads for design codes.This paper outlines this approach and reports the exploratory tests on the effects of surroundings on area and local wind loads. The results show that wind loads in a realistic environment do not always follow the basic wind load characteristics of an isolated building because of interference by neighbouring buildings. The variation of wind loads with wind direction is less severe while the variability due to building location is large. Since expected values are considerably less than the ‘worst case’ data from isolated building tests, these results raise questions concerning the traditional approaches to choosing design loads.
The flow in the atmospheric surface layer is analyzed and discussed with emphasis on those properties which are essential for the prediction of wind loads. Four different flow categories can be recognized which are based primarily on flow observations for various terrain roughness classifications. Simulation of the turbulence is considered to be more essential than simulation of the mean wind profile. Properly conducted boundary layer windtunnel tests need to accommodate the turbulence in each of the four categories, which should also include the small-scale turbulence content in the incident flow. In the case topographic variations control the terrain roughness (complex terrain), current simulation techniques seem to be inadequate.
Pressure measurements near comer edges on a flat roof
- T Stathopoulos
- D Surry
- J.-X Lin
- J R Lankin
T. Stathopoulos, Wind pressures on flat roof edges and comers, Proc. Seventh International Conference on Wind Engineering, Aachen, West Germany, July 1987. D. Surry, J.-X. Lin and J.R. Lankin, Pressure measurements near comer edges on a flat roof, Boundary Layer Wind Tunnel Report, 1991 (University of Western Ontario, London, Ont.) in press.
Wind tunnel tests of a mobile home and comparisons with full scale data
- Johnson
Wind loads on the Aylesbury experimental house: A comparison between full scale and two different model scales
- Vickery
Pressure measurements near corner edges on a flat roof
- Surry