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Wind Load Combinations Including Torsion for Rectangular Medium-rise Buildings
Stathopoulos, T.,Elsharawy, M.,Galal, K. Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.3
This paper presents the results of a set of wind tunnel tests carried out to examine wind-induced overall structural loads on rectangular medium-rise buildings. Emphasis was directed towards torsion and its correlation with peak shear forces in transverse and longitudinal directions. Two building models with the same horizontal dimensions but different gabled-roof angles ($0^{\circ}C$ and $45^{\circ}C$) were tested at different full-scale equivalent eave heights (20, 30, 40, 50, and 60 m) in open terrain exposure for all wind directions (every $15^{\circ}C$). Wind-induced pressures were integrated over building surfaces and results were obtained for along-wind force, across-wind force, and torsional moment. Maximum wind force component was given along with the other simultaneously-observed wind force components normalized by the overall peak. The study found that for flat-roofed buildings maximum torsion for winds in transverse direction is associated with 80% of the overall shear force perpendicular to the longer horizontal building dimension; and 45% of the maximum shear occurs perpendicular to the smaller horizontal building dimension. Comparison of the wind tunnel results with current torsion provisions in the American wind standard, the Canadian and European wind codes demonstrate significant discrepancies. Suggested load combination factors were introduced aiming at an adequate evaluation of wind load effects on rectangular medium-rise buildings.
The numerical wind tunnel for industrial aerodynamics: Real or virtual in the new millennium?
Stathopoulos, T. Techno-Press 2002 Wind and Structures, An International Journal (WAS Vol.5 No.2
Previous studies have shown that Computational Wind Engineering (CWE) is still in its infancy and has a long way to go to become truly useful to the design practitioner. The present work focuses on more recent studies to identify progress on outstanding issues and improvements in the numerical simulation of wind effects on buildings. The paper reviews wind loading and environmental effects; it finds that, in spite of some interesting and visually impressive results produced with CWE, the numerical wind tunnel is still virtual rather than real and many more parallel studies - numerical and experimental - will be required to increase the level of confidence in the computational results.
Wind pressure provisions for gable roofs of intermediate roof slope
Stathopoulos, Theodore,Wang, Kai,Wu, Hanqing Techno-Press 2001 Wind and Structures, An International Journal (WAS Vol.4 No.2
The paper addresses the suitability of wind pressure coefficients specified in contemporary design standards and codes of practice for gable roofs of intermediate slope (roof angle $10^{\circ}-30^{\circ}$). In a recent research study, a series of low building models with different roof slopes in this intermediate range were tested in a boundary layer wind tunnel under simulated open country terrain conditions. This was different from the original study in the 70's, which produced the current provisions on the basis of a model tested only for a single roof slope (4:12) in this range. The results of the study suggest that a modification to the American wind provisions would be warranted to make them more representative of the true local and area-averaged wind loads imposed on gable roofs of intermediate slope.
Effects of upstream two-dimensional hills on design wind loads: A computational approach
Bitsuamlak, G.,Stathopoulos, T.,Bedard, C. Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.1
The paper describes a study about effects of upstream hills on design wind loads using two mathematical approaches: Computational Fluid Dynamics (CFD) and Artificial Neural Network (NN for short). For this purpose CFD and NN tools have been developed using an object-oriented approach and C++ programming language. The CFD tool consists of solving the Reynolds time-averaged Navier-Stokes equations and $k-{\varepsilon}$ turbulence model using body-fitted nearly-orthogonal coordinate system. Subsequently, design wind load parameters such as speed-up ratio values have been generated for a wide spectrum of two-dimensional hill geometries that includes isolated and multiple steep and shallow hills. Ground roughness effect has also been considered. Such CFD solutions, however, normally require among other things ample computational time, background knowledge and high-capacity hardware. To assist the enduser, an easier, faster and more inexpensive NN model trained with the CFD-generated data is proposed in this paper. Prior to using the CFD data for training purposes, extensive validation work has been carried out by comparing with boundary layer wind tunnel (BLWT) data. The CFD trained NN (CFD-NN) has produced speed-up ratio values for cases such as multiple hills that are not covered by wind design standards such as the Commentaries of the National Building Code of Canada (1995). The CFD-NN results compare well with BLWT data available in literature and the proposed approach requires fewer resources compared to running BLWT experiments.
Generalization of wind-induced interference effects for two buildings
Khanduri, Atul C.,Stathopoulos, Theodore,Bedard, Claude Techno-Press 2000 Wind and Structures, An International Journal (WAS Vol.3 No.4
Wind-induced interference effects on a building are the result of one or more adjacent buildings modifying the flow of wind around it, which may result in a significant increase or decrease in wind loads on the building. Wind loading standards and codes of practice offer little guidance to the designer for assessing the effects of interference. Experimental results on interference effects indicate that code recommendations may be significantly low (unsafe) or uneconomically conservative. The paper presents results of an extensive experimental program to study the wind flow mechanisms and to quantify the extent of wind load modifications on buildings due to interference effects. These results have been simplified and presented from the point-of-view of design and codification for the case of two buildings. Based on these results, general guidelines and limiting conditions defining wind interference are formulated and discussed.
Spectral density functions of wind pressures on various low building roof geometries
Kumar, K. Suresh,Stathopoulos, T. Techno-Press 1998 Wind and Structures, An International Journal (WAS Vol.1 No.3
This paper describes in detail the features of an extensive study on Spectral Density Functions (SDF's) of wind pressures acting on several low building roof geometries carried out in a boundary layer wind tunnel. Various spectral characteristics of wind pressures on roofs with emphasis on derivation of suitable analytical representation of spectra and determination of characteristic spectral shapes are shown. Standard spectral shapes associated with various zones of each roof and their parameters are provided. The established spectral parameters can be used to generate synthetic spectra adequate for the simulation of wind pressure fluctuations on building surfaces in a generic fashion.
Generation of local wind pressure coefficients for the design of low building roofs
Kumar, K. Suresh,Stathopoulos, Ted Techno-Press 2001 Wind and Structures, An International Journal (WAS Vol.4 No.6
This paper presents recent research on the experimental evaluation of wind loads on low buildings and the recommendations provided in the form of traditional codification. These mainly include the wind loads on buildings with geometries different from those examined in previous studies. This is followed by the evaluation of simulated wind loads on low building roofs. The overall application of a recently proposed simulation methodology for codification purposes is discussed in detail. The traditional codification provides for a group of roof geometries a single peak design pressure coefficient for each roof zone considering a nominal worst-case scenario; this may often lead to uneconomical loads. Alternatively, the presented methodology is capable of providing peak pressure coefficients corresponding to specific roof geometries and according to risk levels; this can generate risk consistent and more economical design wind loads for specific roof configurations taking into account, for instance, directional design conditions and upstream roughnesses.