Characteristics Of Wind Pressures Research Articles

Measurements on the surface wind pressure characteristics of a thousand-meter scale megatall building by wind tunnel test

This paper investigates the wind pressure distribution of a thousand-meter scale megatall building through a wind tunnel test. One key challenge is that the power-law wind profiles are not applicable due to the height limitation. Therefore, a mesoscale meteorological model WRFv3.4 (Weather Research & Forecasting Model) was used to explore the wind profile covering the height of the thousand-meter scale megatall building. Then the wind profile was reproduced in the wind tunnel representing the actual vertical distribution of wind speed by a passive simulation method, and thereby the wind pressure test was conducted in the wind tunnel. Moreover, to investigate the effect of the inlet wind profile on the wind pressure, a wind tunnel test using the power-law wind profile was carried out for comparison as well. It was revealed that the wind pressure distribution was greatly influenced by the inlet wind profile, which should be investigated with accuracy in the wind tunnel.

RESEARCH ON WIND PRESSURE DISTRIBUTION OF PLASTIC GREENHOUSES IN VALLEY TOPOGRAPHY

As the wind pressure distribution on plastic greenhouses in valley areas is different from that of greenhouses on plains, it is necessary to find out the variation trend of the wind pressure coefficient on greenhouses in the valley areas. Based on the ‘Realizable k-e turbulence’ model, the wind pressure characteristics on plastic greenhouses located in valley and plain areas are studied by using the verified numerical simulation method. The wind pressures on greenhouses and the corresponding fitting formula are obtained for different distances between the greenhouse and the foot of the mountain with a 0-degree wind angle. The results show that, with an increase of distance to the mountain, the positive wind pressure on the windward side of a plastic greenhouse increases and the negative wind pressure on the leeward side, roof surface and crosswind sides of the greenhouse decreases. The results from the proposed formulae are very close to those derived from the numerical simulation method, and the relative errors are all within 10%. The influence of canyon wind on the wind pressure distribution on plastic greenhouses should be considered in the design. This research can provide a reference for the wind resistance design of plastic greenhouses built in valley areas.

Modeling of downburst outflows and wind pressures on a high-rise building under different terrain conditions

This study investigates the characteristics of downburst outflows and wind pressures on a tall building under different terrain conditions. The impinging jet (IJ) facility was utilized to experimentally reproduce the spatial velocity distribution of the downburst-like winds. Varying terrain exposures were explicitly modelled by appropriately arranging the roughness elements on the ground. In addition, large-eddy simulations (LES) combined with both the IJ model and cooling source (CS) model were performed to elucidate the characteristics of microburst flow fields over rough grounds. For investigating the aerodynamic loadings of a tall building immersed in downburst-like winds, the wind pressures of a rigid building model were synchronously measured under different terrain exposures. The results were found that rough terrain played a retarding role on the microburst-like winds in the inner core regions near the ground and its drag effects gradually decreased in the outburst regions with the radial separation distance from the center of the impinging jet. The height where maximum radial velocity occurred increased with the increasing roughness of terrain conditions, but the maximum wind speed was reduced evidently. The distribution patterns of the mean pressure on the windward surface were significantly influenced by rough terrains due to the differences among the vertical profiles of radial velocity component under varying terrain exposures. The maximum pressure fluctuations on the tested model were found to occur further downstream from the center of microburst winds, which was caused by the effect of intensified second-vortex. The outcomes of this study are of great use to improve the understanding of the effects of terrain roughness on downburst winds and the corresponding aerodynamic loads of tall buildings.

Prediction of wind pressures on tall buildings using wavelet neural network

For wind-resistant design of tall buildings, it is routine to obtain complete surface wind pressure distribution based on experimental data recorded at limited locations. The main goal of this study is to examine the usability of a hybrid artificial neural network method, i.e., Wavelet Neural Network (WNN), for simulating and interpolating wind pressures on tall buildings. Wind pressure measurement tests were carried out on two scaled tall building models. The performance of three different prediction models, namely back-propagation neural network (BPNN), genetic algorithm-back-propagation neural network (GA-BP), and WNN were examined for comparison purposes. The results are overall promising, in which all the three models were capable to reasonably replicating wind pressure characteristics (i.e., time series, power spectra and wind pressure coefficient distribution) using experimental data at selected locations. In particular, WNN was shown to produce the most satisfactory prediction results. This evidences that WNN can be considered as a useful and reliable tool to predict surface wind pressure on tall buildings. The outcomes of this study are expected to provide important implications to practically aid the wind-resistant design of tall buildings.

Experimental Investigation of Wind Pressure Characteristics for Cladding of Dome Roofs

Cladding for dome roofs is often made of membrane materials that are light and easy to install. Due to these characteristics, wind damage to dome roof cladding is very common. In particular, open or retractable dome roofs are prone to wind damage because of inadequacies in wind load calculations. In this study, the wind pressure characteristics of a dome with a central opening were investigated. Wind tunnel tests were performed, and the pressure distribution was investigated by analyzing external and internal pressure coefficients. Based on the experimental results, the peak net pressure coefficients for the cladding design of a dome roof with a central opening were proposed. For the external peak pressure coefficients, the values of leeward regions were similar despite height–span ratios and turbulence intensity values. For the internal peak pressure coefficients, negative pressure was dominant, and the coefficients were not significantly affected by changes in height–span ratio. This tendency locally increased the negative peak net pressure, in which the load acts in the upward direction, and relatively significantly increased the positive peak net pressure, in which the load acts in the downward direction.

Experimental investigation of wind pressure characteristics and aerodynamic optimization of a large-span cantilevered roof

Cantilevered roof is particularly vulnerable to wind because high suction loads often occur on the rooftop due to flow separation. However, wind load characteristics associated with cantilevered roof have not been fully understood. In this paper, a 1/100 scale model of a cantilevered roof, over a grandstand, has been tested in a turbulent boundary layer flow, with particular emphasis on characterizing the wind pressure distribution on the cantilevered roof, and assessing the performance of several aerodynamic optimization devices. The results indicate that large wind suction generally occurs near the windward edge on rooftop surface. The effect of approaching wind direction is evident, which can influence the distribution pattern and value of wind pressure. For the effect of roof inclination, the down-sloping roof is found to be more appropriate since it results in most significant reduction in mean wind pressure, as well as the net lifting and bending moment coefficients. Furthermore, it is shown that adding a vented leading edge slot can effectively reduce the rooftop wind suctions. The maximum reduction in mean and peak suction loads is respectively 30% and 45%.

Wind pressure characteristics of elliptical retractable dome roofs

This study investigated the wind pressure characteristics of an elliptical plan retractable dome roof. Wind tunnel experiments were performed on elliptical dome roofs with varying wall height-to-span ratios (0.1–0.5) and opening ratios (0, 10, 30, and 50 %), where the opening ratio was defined as the ratio of the open area of the roof to the total area of the roof. The resulting peak pressure coefficients of the closed dome roof were then compared with those of the Japanese wind load code (AIJ-RLB (2015)) as there are no current peak pressure coefficients for the cladding design code of elliptical dome roofs. The resulting peak pressure coefficients for each elliptical retractable dome roof opening ratio were also compared with those for the cladding design of spherical retractable domes proposed in previous research. Finally, based on the results of the comparative analysis, negative and positive peak pressure coefficients were proposed for the cladding design of elliptical retractable dome roofs.

Extreme estimation of wind pressure with unimodal and bimodal probability density function characteristics: A maximum entropy model based on fractional moments

The complicated probability density function (PDF) characteristics of wind pressure, including its highly skewed, highly leptokurtic, and bimodal characteristics induced by sophisticated architecture, call for improved extreme-estimation models. Most existing methods are based on a unimodal PDF's underlying assumption and fail in highly non-Gaussian cases. Owing to the complete probabilistic information used in cumulative distribution function (CDF)-mapping methods, such methods have the potential to deal with complicated PDF-type wind pressures. To yield better curve-fitting of the parent distribution, which is the critical step of CDF-mapping, a maximum entropy model based on fractional moments is combined with CDF-mapping in this work. By using the Legendre-Gauss quadrature rule, the computational efficiency of fitting parent distribution is improved. The model's performance is benchmarked against typical long-term wind pressure data obtained from wind tunnel tests conducted at a long-span airport terminal model. By considering the captured probability properties, four typical taps are selected to provide empirical wind-pressure extreme in the 57% fractile for detailed model assessment. The confidence intervals of the estimated results and errors for all taps are also calculated. Compared with existing polynomial-fitting- and CDF-mapping-based translation methods, the extreme estimated by the proposed method are shown to be more robust and stable. • A novel approach was proposed for extreme estimation of wind pressures with unimodal and bimodal cases. • The Legendre-Gauss quadrature rule was adapted for improving the model computational efficiency. • The model performance was verified with long-term measured data from the wind tunnel test of a long-span building. • A detailed comparison against existing translation-based methods was conducted.

Pressure pattern recognition in buildings using an unsupervised machine-learning algorithm

Owing to its significance in ensuring structural safety and occupant comfort, wind pressure on buildings has attracted the attention of numerous scholars. However, the characteristics of wind pressures are usually complex. This study employs an unsupervised machine-learning algorithm, clustering algorithms, to study wind pressures on buildings. Wind pressures on a single building and two adjacent buildings with different gaps are measured in a wind tunnel, with clustering algorithms applied to cluster different wind pressure patterns. The results show that for the single-building model, the pressure patterns are symmetrical on the side surfaces of the building; for the two-building model with a small gap, a channeling effect can be identified; for the two-building model with a large gap, the pressure patterns shared symmetry with that of the single-building model. Clustering algorithms can recognize unidentified patterns of wind pressures on buildings. This study demonstrates that clustering algorithms are a powerful tool for recognizing patterns hidden in complex pressure fields and flow fields. Therefore, this study proposes a promising machine-learning technique that can perfectly complement traditional building methods using wind engineering. • Applied machine learning algorithm for recognizing wind pressure patterns. • Aerodynamic characteristics on buildings were investigated. • Alongwind and crosswind pressure coefficients of buildings were analyzed. • Impact of pressure coefficients on two building with different gap width was analyzed.

EFFECTS OF SPOILER ON WIND LOAD OF FLAT ROOFS EXPOSED TO SEPARATION BUBBLE

Through wind tunnel test, wind pressure characteristics of flat roofs exposed to separation bubble with or without spoilers were investigated and compared. Based on this, the mechanism of the spoiler for reducing wind-induced effect and the recommended inclination were given. Distribution and statistics of wind pressures were demonstrated. It is shown that the mean and fluctuating pressures are reduced by setting the spoilers, except those near the leading edge. In the separated region, the skewness and kurtosis of wind pressures significantly decrease, which implies the less obvious non-Gaussian nature. The influence of spoilers on wind pressure correlation was analyzed. It is observed that the longitudinal correlation attenuates dramatically, while the degenerative transverse correlation only occurs near the leading edge. The variation of total uplift forces and overturning moment were given. For the spoilers with inclination of 0°, 10° and 20°, the total mean uplift forces are decreased by 6.3%, 8.2% and 6.6% respectively, the total mean overturning moment are decreased by 18.2%, 21.9% and 23.3% respectively. With the obtained wind loads, the static response analysis was conducted. It is demonstrated that the axial force at the column bottom, the moment at the column bottom and the displacement at the roof center can be reduced by up to 13.1%, 15.6% and 10.1% respectively. Based on the statistics, the correlation, the total force, and the structural internal force, the recommended inclination of spoilers on flat roofs is 10° within the investigated scope.

Analysis of Wind Pressure Characteristics of Retractable Dome Roof by Opening Type Through Wind Tunnel Test

Analysis of Wind Pressure Characteristics of Retractable Dome Roof by Opening Type Through Wind Tunnel Test

Experimental Study of Wind Pressure on a Long-Span Canopy Roof Structure Using a Wind Tunnel

The wind pressure characteristics of the surface of a long-span canopy roof structure were investigated in detail using synchronized pressure measurement tests on a rigid model in an atmospheric boundary layer wind tunnel. The mean and fluctuating wind pressure distribution characteristics, power spectral density and coherence of the fluctuating wind pressure between different measurement points were analyzed. The results showed that the wind direction had a significant impact on the wind load distribution across the surface of the long-span canopy roof structure. When the short axis of the roof structure faced the wind, a positive pressure area was formed under the impact of the incoming flow, with the resulting turbulence being the main cause of excitation. When the long axis of the roof structure faced the wind (wind directions of 0° and 180°), a columnar vortex was formed on the windward side of the front edge of the roof structure and a suction force was created at the separation points, with the main excitation of the wind load being intermittent vortex shedding. The resulting spectral content was complex. The coherence of the measurement points on the roof structure surface decreased continuously as the distance between them increased. The correlation between the same two measurement points obviously also differed according to the wind direction. However, the coherence between measurement points aligned to the wind direction was stronger than it was in a cross-wind direction.

Bimodal distribution of wind pressure on windward facades of high-rise buildings induced by interference effects

Understanding the characteristics of wind pressures on structural façades is of great importance for wind-resistant design of claddings and glass curtains of buildings. This article presents some interesting findings about the behavior of wind pressure on the façades of a high-rise building influenced by an interference building via wind tunnel tests. The bimodal probability distribution (BPD) of wind pressure acting on the windward side of the principal building is highlighted, which has been rarely reported and investigated in previous studies. This BPD featured wind pressure consists of both positive and negative components that alternate along time in a consistent way to the vortex shedding downwind of the interference building. By changing the relative position between the principal building and interference building, it is observed that the bimodal distribution can be transformed to a unimodal form, mostly with a long tailed on the left-hand-side of the probability-density-function (PDF). Based on the above findings, this study proposes a mixture PDF model which is actually a combination of the Gaussian model and the generalized-extreme-value (GEV) model. While the Gaussian PDF accounts for the component dominated by the background approaching flows, the GEV one is associated with the aerodynamic interference effects. Parametric analysis is then conducted for the BPD feature based on the proposed mixture model, and detailed process for the transformation of different PDF patterns (from varied bimodal patterns to both Gaussian and tailed unimodal statuses) is reproduced. The findings can provide useful insights for the wind-resistant design of claddings and curtain walls of high-rise buildings, and for further analyzing non-Gaussian characteristics of wind pressure, such as for estimating extreme pressure values.

Characteristics of conical vortices and their effects on wind pressures on flat-roof-mounted solar arrays by LES

Large eddy simulations (LES) are performed to examine the flow characteristics around solar arrays mounted on a flat-roof building for two oblique wind directions, 45° and 135°. The main purpose of this study is to clarify the mechanisms of some special features of wind pressure characteristics acting on solar panels obtained by wind tunnel experiments. Numerical simulation is first conducted for a flat-roof building without solar arrays to validate the accuracy of LES for oblique wind directions. Numerical simulations are then made for a flat-roof building with solar arrays. For 45° wind direction, local separations and reattachments of the downflows of the left-side conical vortex are found to play important roles in large negative pressures near the higher edges of the upper surfaces and positive pressures on some parts of the lower surfaces of solar panels. For 135° wind direction, local vortices generated from the higher edges of the solar panels form local wake regions downwind of the panels and cause downward net pressures on most of the panels. The effects of the gaps on pressures on the upper surfaces of solar arrays are not significant, but those on the lower surfaces are significant because of the flows passing under the panels.

Research on the characteristics of wind pressures on L-shaped tall buildings

Eight L-shaped rigid models with different geometric dimensions were tested at four typical terrain categories in a boundary wind tunnel to investigate the characteristics of wind pressures on L-shaped tall buildings. The effects including wind direction, turbulence intensity, and geometric dimension on the characteristics of wind pressures on L-shaped tall buildings were studied. Shape factors of each face under the unfavorable wind direction were summarized. Moreover, the power spectral densities, correlation coefficients, and coherence functions were analyzed in frequency domain. Based on the testing results, it is shown that the proposed exponential functions fit the measurements well. The objective of this study is to provide useful information for the wind-resistant design ofL-shaped tall buildings.

LES study of wind pressure and flow characteristics of flat-roof-mounted solar arrays

Wind loading is a major concern for solar array systems. To clarify the relations between flow field and wind pressure distributions on solar panels, large eddy simulations (LES) are performed to examine the flow characteristics around solar arrays mounted on a flat roof building for two normal wind directions, 0° and 180°. The mean, standard deviation and peak value of pressure and force coefficients obtained from LES and wind tunnel experiment are firstly compared to validate the accuracy of LES. Then the mean and unsteady flow fields around solar arrays are discussed to explain the corresponding wind pressure distributions. The local separation at the higher edges of solar panels located inside of both the separation bubble and the reattached flow are detected. The wind pressures on upper and lower surfaces of solar panels resulted by the local flow field are discussed accordingly for different scenarios. Ensemble-averaged flow fields on the condition of the occurrence of peak pressures at the higher edge of solar panels are also investigated. It is found that besides the large-scale separating and reattaching flow induced by the building, small-scale local separations at the higher edges of the solar panels are also responsible for the large peak of uplift.

Numerical and experimental study of the aerodynamic characteristics around two-dimensional terrain with different slope angles

Complicated terrain was considered and simplified as two-dimensional (2D) terrain in a dynamical downscaling model and a parametric wind field model for typhoons developed by the Shanghai Typhoon Institute. The 2D terrain was further modeled as uphill and downhill segments with various slope angles relative to the incoming flow. The wind speed ratios and pressure characteristics around the 2D terrain were numerically and experimentally investigated in this study. Aerodynamic characteristics of the 2D terrain with a limited-length upper surface were first investigated in the wind tunnel with sheared incoming flow. The corresponding numerical investigation was also conducted by using the commercial computational fluid dynamics code FLUENT with the realizable k-e turbulence model. Special efforts were made to maintain the inflow boundary conditions throughout the computational domain. Aerodynamic characteristics were then investigated for the ideal 2D terrain with an unlimited-length upper surface by using a numerical method with uniform incoming flow. Comparisons of the different terrain models and incoming flows from the above studies show that the wind pressure coefficients and the wind speed ratios are both affected by the slope angle. A negative peak value of the wind pressure coefficients exists at the escarpment point, where flow separation occurs, for the uphill and downhill terrain models with slope angles of 40° and 30°, respectively. Correspondingly, the streamwise wind speed ratios at the points above the escarpment point for the uphill terrain model increase with increasing slope angle, reach their peak values at the slope angle of α = 40° and decrease when the slope angle increases further. For the downhill terrain model, similar trends exist at the points above the escarpment point with the exception that the critical slope angle is a = 30°.

Typhoon-Induced Wind Pressure Characteristics on Large Terminal Roof Based on Mesoscale and Microscale Coupling

AbstractLocal roof failure is the most typical form of wind-induced failure of large-span terminals, especially in southeast coastal regions with frequent occurrence of strong typhoons. Since exist...

Non-Gaussian Features of Local Wind Pressure for Typical Gable Roof of Low-rise Building

The non-Gaussian characteristics of local wind pressure of typical gable roof of low-rise building with a slop angle of 18.4° were monitored by means of the wind tunnel test under terrain roughness regimes of A,B and C. The probability density distribution features of wind pressure coefficient series are investigated, the characteristics of non-Gaussian zones distribution of wind pressure relative to different wind angles and different terrain conditions are analyzed and the relationships between non-Gaussian pressure and distinctions of flow field on roof are discussed. The studying results indicate that GEV distribution and Gamma distribution fit the probability density distribution of wind pressure coefficient better than Gaussian distribution and Lognormal distribution, but the fitting effect for long trailing tail part is undesirable, when skewness and kurtosis are large in magnitude (absolute value). The variation of terrain roughness and wind directions have significant influence on the distribution of non-Gaussian pressure regions on low-rise building roof. Under the oblique wind direction, the Gaussian pressure zone is divided into three sections along the approaching wind direction, along which the areas move with the change of terrain roughness regimes. The non-Gaussian features of wind pressure is positively related to mutual correlation coefficient of it’s time-history.

Characteristics of wind pressures on retractable dome roofs and external peak pressure coefficients for cladding design

This study investigates the characteristics of wind pressures on retractable dome roofs. Wind tunnel tests were conducted on spherical dome roofs with various wall height-span ratios (0.1–0.5) and opening ratios (0%, 10%, 30% and 50%). After the characteristics of mean and peak pressure coefficients were examined, the peak pressure coefficients on closed dome roofs were compared with those of the current Japanese wind load code (AIJ-RLB (2015)), and peak pressure coefficients on dome roofs with openings for cladding design were proposed. The analysis results can be summarized as follows. As wall height-span ratio increases, the absolute values of mean and minimum pressure coefficients increase, and the absolute values of minimum pressure coefficients on the outermost interior of open dome roofs increase with opening ratio. For cladding design of dome roofs with openings, dome roofs were divided into two zones, and negative and positive peak pressure coefficients were proposed based on experimental results.