Pressure modes for hyperbolic paraboloid roofs

2020 ◽  
Vol 7 (1) ◽  
pp. 226-246
Author(s):  
Fabio Rizzo ◽  
Cristoforo Demartino
Keyword(s):  
Pressure Coefficient ◽  
Measured Signal ◽  
Hyperbolic Paraboloid ◽  
Pressure Coefficients ◽  
Truncated Svd ◽  
Mean Pressure ◽  
Vertical Displacements ◽  
Value Decomposition ◽  
Experimental Pressure ◽  
Polynomial Surface

AbstractThis paper presents a study on Singular Value Decomposition (SVD) of pressure coefficients hyperbolic parabolic roofs. The main goal of this study is to obtain pressure coefficient maps taking into account spatial non-uniform distribution and time-depending fluctuations of the pressure field. To this aim, pressure fields are described through pressure modes estimated by using the SVD technique. Wind tunnel experimental results on eight different geometries of buildings with hyperbolic paraboloid roofs are used to derive these pressure modes. The truncated SVD approach was applied to select a sufficient number of pressure modes necessary to reconstruct the measured signal given an acceptable difference. The truncated pressure modes are fitted through a polynomial surface to obtain a parametric form expressed as a function of the hyperbolic paraboloid roof geometry. The superpositions of pressure (envelopes) for all eight geometry were provided and used to modify mean pressure coefficients, to define design load combinations. Both symmetrical and asymmetrical pressure coefficient modes are used to estimate the wind action and to calculate the vertical displacements of a cable net by FEM analyses. Results clearly indicate that these load combinations allow for capturing large downward and upward displacements not properly predicted using mean experimental pressure coefficients.

scholarly journals Mode Pressure Coefficient Maps as an Alternative to Mean Pressure Coefficient Maps for Non-Gaussian Processes: Hyperbolic Paraboloid Roofs as Cases of Study

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 64 ◽  
Author(s):  
Alberto Viskovic
Keyword(s):  
Gaussian Processes ◽  
Pressure Coefficient ◽  
Wind Tunnels ◽  
Wind Tunnel Experiments ◽  
Hyperbolic Paraboloid ◽  
Mean Values ◽  
Parabolic Shape ◽  
Mean Pressure ◽  
The Mean ◽  
Non Gaussian

Wind tunnel experiments are necessary for geometries that are not investigated by codes or that are not generally and parametrically investigated by literature. One example is the hyperbolic parabolic shape mostly used for cable net roofs, for which codes do not provide pressure coefficients and literature only gives mean, maxima, and minima pressure coefficient maps. However, most of pressure series acquired in wind tunnels on the roof are not Gaussian processes and, for this reason, the mean values are not precisely representative of the process. The paper investigates the ratio between mean and mode of pressure coefficient series acquired in wind tunnels on buildings covered with hyperbolic paraboloid roofs with square plans. Mode pressure coefficient maps are given as an addition to traditional pressure coefficient maps.

Wind Loading on Catenary Domes

2019 ◽  
Author(s):  
Richard M. van Gool ◽  
Ryan A. Bradley ◽  
Mitchell Gohnert
Keyword(s):  
Pressure Coefficient ◽  
Wind Loading ◽  
Pressure Coefficients ◽  
Hemispherical Dome ◽  
Circular Profile ◽  
Mean Pressure ◽  
Efficient Alternative ◽  
Base Radius ◽  
The Mean ◽  
Layer Flow

<p>Catenary domes are a less conventional, but structurally efficient, alternative to traditional circular-profile domes. Unlike the more common circular forms, there is a dearth of wind loading information for catenary structures. This paper aims to provide some insight in this regard. A series of wind tunnel tests were undertaken to investigate the effects of geometry and Reynolds number on the mean pressure coefficient distributions over catenary domes in a turbulent boundary layer flow. A hemispherical dome was also assessed, and the results compared with that for the catenary shapes. These parameters were evaluated to elucidate their influence on the loading on these structures. Only the results relating to mean pressure coefficients are reported in this paper. An important finding was that the height to base radius (H/R) of the catenary dome had a substantial influence on the mean pressure coefficient distributions over the structure. Finally, the results of the investigation and their implications on the design of catenary domes are discussed. This may be of value to designers because at present no wind loading information exists for catenary domes</p><p>– at least to the author’s knowledge.</p>

scholarly journals Probability Characteristics, Area Reduction, and Wind Directionality Effects of Extreme Pressure Coefficients of High-Rise Buildings

2021 ◽  
Vol 11 (15) ◽  
pp. 7121
Author(s):  
Shouke Li ◽  
Feipeng Xiao ◽  
Yunfeng Zou ◽  
Shouying Li ◽  
Shucheng Yang ◽  
...  
Keyword(s):  
Probability Distribution ◽  
Pressure Coefficient ◽  
Wind Pressure ◽  
Extreme Pressure ◽  
Distribution Law ◽  
Distribution Fitting ◽  
Pressure Coefficients ◽  
High Rise ◽  
Area Reduction ◽  
The Mean

Wind tunnel tests are carried out for the Commonwealth Advisory Aeronautical Research Council (CAARC) high-rise building with a scale of 1:400 in exposure categories D. The distribution law of extreme pressure coefficients under different conditions is studied. Probability distribution fitting is performed on the measured area-averaged extreme pressure coefficients. The general extreme value (GEV) distribution is preferred for probability distribution fitting of extreme pressure coefficients. From the comparison between the area-averaged coefficients and the value from GB50009-2012, it is indicated that the wind load coefficients from GB50009-2012 may be non-conservative for the CAARC building. The area reduction effect on the extreme wind pressure is smaller than that on the mean wind pressure from the code. The recommended formula of the area reduction factor for the extreme pressure coefficient is proposed in this study. It is found that the mean and the coefficient of variation (COV) for the directionality factors are 0.85 and 0.04, respectively, when the orientation of the building is given. If the uniform distribution is given for the building’s orientation, the mean value of the directionality factors is 0.88, which is close to the directionality factor of 0.90 given in the Chinese specifications.

CFD Modeling of Pressure Coefficients for a Natural Ventilation Study in an Experimental Low Rise Building

2013 ◽  
Author(s):  
Robel Kiflemariam ◽  
Cheng-Xian Lin
Keyword(s):  
Natural Ventilation ◽  
Pressure Coefficient ◽  
Wind Pressure ◽  
Analytical Models ◽  
Cfd Modeling ◽  
Engineering Practice ◽  
Pressure Coefficients ◽  
Wind Pressure Coefficient ◽  
Detailed Assessment ◽  
Ventilation Rates

Mean wind pressure coefficient (Cp) is one of the major input data for natural ventilation study using building energy simulation approach. Due to their importance, they need to be accurately determined. In current engineering practice, tables and analytical Cp models only give mostly averaged results for simpler models and configurations. Considering the limitation of tables and analytical models, Computational Fluid Dynamics (CFD) could provide a means for an accurate and detailed assessment of Cp. In this paper, we make use of a relatively high resolution, detailed experiments done at Florida Intentional University to validate a CFD modeling of the pressure coefficients Cp. The results show that existing CFD model has a good agreement with experimental results and gives important information of distribution of Cp values over the surface. The local values of the Cp are investigated. In addition, the CFD derived Cp and discharge coefficient (Cd) values are utilized in semi-analytical ventilation models in order to get a more accurate value of ventilation rates.

scholarly journals Computational assessment of wind flow field on and around atypical buildings

2020 ◽  
Author(s):  
Rajasekarababu KB
Keyword(s):  
Surface Pressure ◽  
Pressure Coefficient ◽  
Tall Buildings ◽  
Ground Level ◽  
Pressure Variation ◽  
Middle Level ◽  
Computational Results ◽  
Pressure Coefficients ◽  
Building Surfaces ◽  
Side Face

Abstract This article provides an overview of pressure coefficients ( Cp ) on atypical tall buildings with the application of CFD. Various modifications in architectural shapes on tall buildings eventually lead to a reduction in the wind load on building surfaces. The surface pressure on conventional (Square and rectangular) buildings is relatively different in comparison to other tall buildings. This study is to evaluate the surface pressure coefficient over rectangular, taper and setback buildings. The computational results show that the taper building has 7% Cp rise at ground level ( y/H= 0.225) in the windward face, and 34% Cp fall at the middle level ( y/H= 0.475) in the side face when compared with the rectangular building. Whereas for the setback building, Cp at ground level near setback ( y/H= 0.225) has reduced to about 25% and about 6% at the middle level ( y/H= 0.475) in windward than that in the rectangle building. Also, the side faces of the setback showed a 15% drop in Cp than other buildings. In leeward face, Cp is reduced to 56% near setback at the top of the building ( y/H= 0.725). This valuation of the Cp on these buildings shows that the effect of setbacks on building reduces the pressure variation on all faces and the downstream wake vortices.

Wind tunnel test on mean wind forces and peak pressure acting on ellipsoidal nacelles of wind turbine

2021 ◽  
pp. 0309524X2110445
Author(s):  
Hiroshi Noda ◽  
Takeshi Ishihara
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Peak Pressure ◽  
Wind Tunnel Test ◽  
Load Case ◽  
Wind Force ◽  
Pressure Coefficients ◽  
Force Coefficients ◽  
Design Load ◽  
Mean Pressure

Mean wind forces and peak pressures acting on ellipsoidal nacelles are investigated by wind tunnel tests. The wind force coefficients of the ellipsoidal nacelles for the wind turbine design and the peak pressure coefficients for the nacelle cover design are proposed based on the experimental data. The wind force coefficients are expressed as functions of yaw angles. The proposed formulas are compared with Eurocode, Germanischer Lloyd and ASCE7-16. It is found that the mean wind force coefficients for the wind turbine nacelles are slightly underestimated in Eurocode. The equivalent maximum and minimum mean pressure coefficients are proposed for use in Design Load Case 6.1 and Design Load Case 6.2 of IEC 61400-1. The peak pressure coefficients are derived using a quasi-steady theory. The proposed equivalent maximum and minimum mean pressure coefficients are much larger than those specified in Germanischer Lloyd.

scholarly journals Hemp Cables, a Sustainable Alternative to Harmonic Steel for Cable Nets

Resources ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 70 ◽  
Author(s):  
Alberto Viskovic
Keyword(s):  
Three Dimensional ◽  
Structural Response ◽  
Building Design ◽  
Structural Elements ◽  
Nonlinear Analyses ◽  
Hyperbolic Paraboloid ◽  
Materials Engineering ◽  
Recent Developments ◽  
Vertical Displacements ◽  
Cable Nets

Recent developments in the field of materials engineering have allowed for the use of natural materials for common structural elements, instead of traditional materials, such as steel or concrete. In this context, hemp is a very interesting material for structural building design. This paper proposes the use of hemp cables for roofs with hyperbolic paraboloid cable nets, which sees the use of a sustainable material for structure, thus having a very low environmental impact, in terms of structural thickness and amount of material. The paper discusses five different plan sizes and two different hyperbolic paraboloid surface radius of curvatures. The cable traction, which gives the cable net stiffness, was varied in order to give a parametric database of structural response. Three dimensional geometrically nonlinear analyses were carried out on different geometries (i.e., 10), cable net stiffnesses (i.e., 8), and materials (i.e., 2). Traditional harmonic steel and hemp cables are compared, in terms of vertical displacements and natural periods under dead and permanent loads.

Investigation of Supercritical Flow and Shape of Flip Bucket Spillways on Coefficients of Dynamic Pressure

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Hessam Vatandoust ◽  
Hamidreza Yarmohammadi ◽  
Mohammadreza Kavianpour
Keyword(s):  
Froude Number ◽  
Pressure Fluctuation ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Pressure Fluctuations ◽  
Experimental Studies ◽  
Flow Speed ◽  
Middle Part ◽  
Statistical Characteristics ◽  
Pressure Coefficients

Abstract Pressure fluctuation is one of the major turbulent flow characteristics. It may cause crucial problems for hydraulic structures. This research is based on experimental studies, and it focuses on the measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. The function of the flip bucket spillway is discharging floods from reservoir dams which are energy storage source measurements of dynamic pressures on three different models of flip buckets that were performed for this investigation. Pressure fluctuation of the flip buckets have been measured within a range of Froude numbers from 5 to 13 (Fr = u/gy, where u is the flow speed, y is the depth, and g is 9.81 m/s2). Statistical characteristics of pressure fluctuations, the location, and the values of maximum and minimum fluctuations have also supplemented the study. The results show that the coefficients of pressure fluctuations (Cp = RMS/(0.5(u2/g)) where RMS is the root-mean-square of pressure fluctuation, u is the flow speed, and g is 9.81 m/s2) reduce as the Froude number (Fr) of flow increases, except a maximum Froude number. Pressure coefficients increase along the flip bucket with incremental mutations in the transformation area of the flip bucket. In the middle part of the flip bucket spillway, pressure coefficient values decrease. Additionally, as B/r (B is the width of the flip bucket and r is the radius of the flip bucket) ratio increases, pressure coefficients become larger and this process continues along the flip bucket.

Chip-on-Beam and Hydrostatic Calibration of the Piezoresistive Coefficients on (111) Silicon

2007 ◽  
Author(s):  
Chun-Hyung Cho ◽  
Richard C. Jaeger ◽  
Jeffrey C. Suhling ◽  
M. Kaysar Rahim
Keyword(s):  
Pressure Coefficient ◽  
Experimental Methods ◽  
Temperature Dependent ◽  
Pressure Coefficients ◽  
Stress Sensors ◽  
Wide Range ◽  
Complete Set ◽  
Stress Sensing ◽  
Test Chips ◽  
P Type

Stress sensing test chips are used to investigate die stresses arising from assembly and packaging operations. The chips incorporate resistor or transistor sensing elements that are able to measure stresses via the observation of the changes in their resistivity/mobility. The piezoresistive behavior of such sensors is characterized by three piezoresistive (pi) coefficients, which are electro-mechanical material constants. Stress sensors fabricated on the surface of the (111) silicon wafers offer the advantage of being able to measure the complete stress state compared to such sensors fabricated on the (100) silicon. However, complete calibration of the three independent piezoresistive coefficients is more difficult and one approach utilizes hydrostatic measurement of the silicon “pressure” coefficients. We are interested in stress measurements over a very broad range of temperatures, and this paper present the experimental methods and results for hydrostatic measurements of the pressure coefficient of both n- and p-type silicon over a wide range of temperatures and then uses the results to provide a complete set of temperature dependent piezoresisitive coefficients for the (111) silicon.

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