Wind Tunnels: Aerodynamics, Models and Experiments
Author: Justin D. Pereira, | Size: 7.37 MB | Format:PDF | Quality:Unspecified | Publisher: Nova Science Publishers, Inc. | Year: 2011 | pages: 240 | ISBN: 9781619423299
This book presents current research in the study of wind tunnels, including the design, execution and numerical rebuilding of a plasma wind tunnel with the aim to analyse shock wave boundary layer interaction phenomena; the Mainz vertical wind tunnel facility experimenting on cloud physics and chemistry; an air-conditioned wind tunnel environment for the study of mass and heat flux; using wind tunnel studies to evaluate the drag coefficient of the tree crown and Pre-X aerodynamic/aerothermal characterisation through computational fluid dynamics and wind tunnels.
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Adequate bond between prestressing strand and concrete is essential for adequate structural performance and reliability of concrete members. Bond quality affects transfer and development lengths of prestressed members. If the bond between the strand and concrete is not enough, the transfer and development length of the member may exceed the code requirement. Hence non ductile failure occurs due to inadequate shear reinforcement provision. Researchers found the current code equations governing the bond of strand have been shown to be inaccurate. Hence bond test is needed that will help to determine the effects on bond of variations in concrete properties or constituent materials. The Prestress Concrete Institute (PCI) financed projects that investigated strands manufactured by various manufacturers using various test methods. Research conducted by Cousin,
Johnson and Zia indicates that the ACI code equations for bond might be inadequate and more research is needed to fully understand the bond mechanics between concrete and
prestressing strand. According to Mote (2001), concrete strength would affect bond of prestessing strand.
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The trends for analysis and design of steel frames are indicated in this dissertation. The current practice consists of applying the first-order elastic analysis with amplification factors or second-order elastic analysis in combination with the AISC-LRFD interaction ·
equations. Determination of the effective length factors and individual member capacity checks are necessary to select adequate structural member sizes. The direct analysis method is a second-order elastic analysis approach that eliminates the determination of effective length factors from the current AISC-LRFD method. Unsupported member length is used to calculate the axial strength of a member. Equivalent notional loads
and/or modified stiffuess are applied together with the external loads to account for the effects of initial out-of-plumbness and inelastic softening. For both AISC-LRFD and direct analysis methods, a structure is analyzed as a whole, but the axial and flexural strength of each member is examined individually. Inelastic redistribution of internal forces in the structural system cannot be considered. As a result, determined member forces are not correct and more conservative member sizes will be obtained. Moreover, member-based approaches cannot predict structural behaviors such as failure mode and overstength factor.
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ANALYSIS OF RADIO COMMUNICATION TOWERS SUBJECTED TO WIND, ICE AND SEISMIC LOADINGS
Author: ERIC JAMES SULLINS | Size: 2.69 MB | Format:PDF | Quality:Unspecified | Publisher: ERIC JAMES SULLINS | Year: 2006 | pages: 117
The Missouri Department of Transportation radio communication tower network is currently out of date with respect to current tower building codes. The network was created in the 1950s and 1906s as part of the U.S. military civil defense system. The network was designed using the TIA-222-C (1976) or earlier. Today the current code in practice is the TIA-222-F (1996) code. There is a need to assess the condition of the towers in the network and also to determine if they are up to date with current code. A condition indexing (CI) system is a reliable way to assess this problem. However, an analytical method of determining the input parameters for the CI needs to be determined.
Therefore the objective of this research is to develop a systematic evaluation and assessment method that could provide the necessary information for the repair and maintenance of the tower network.
Two towers were selected for this project to act as model towers. One tower is guyed, the Taum Sauk tower, and the other is freestanding, Kansas City tower. Both towers are analyzed using the TIA-222-F for wind and ice loadings. The Taum Sauk tower is then analyzed for seismic loading. Also a parametric study to determine the effects of deterioration of tower components on the tower as a whole is completed on the Taum Sauk tower.
The controlling components of the Kansas city tower were found to be the diagonal bracings. The critical bracings were found to be at 88.9% of their maximum capacity. The maximum capacities of the other components of the tower were found not
to exceed 51.1% capacity. Therefore, the tower passes for the current code.
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Computation of Wind Flow around a Tall Building and the Large--Scale Vortex Structure
Author: CHARLES C. S. SONG, JIANMING HE | Size: 648 KB | Format:PDF | Quality:Unspecified | Publisher: CHARLES C. S. SONG, JIANMING HE | Year: 1993 | pages: 10
A numerical study of three-dimensional wind flow around a tall building is presented in this paper. The solution is obtained by solving weakly compressible flow equations, along with Smagorinsky's subgrid-scale turbulent model. The numerical
scheme is based on MacCormack's predictor-corrector explicit finite volume method. First, the numerical model was verified by testing a shear flow around surface--mounted cube, then a detailed study was carried out for a shear flow around a taller building model (width:length:height = 1:0.889:4.667). The main task of this paper is to explore the large-scale vortex structure and the unsteady behavior of flow around a tall building, which are still not well understood.
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STRUCTURAL DAMAGE ASSESSMENT OF BUILDING STRUCTURES USING DYNAMIC EXPERIMENTAL DATA
Author: HEUNG-SIK KIM AND YOUNG-SOO CHUN | Size: 163 KB | Format:PDF | Quality:Unspecified | Publisher: HEUNG-SIK KIM AND YOUNG-SOO CHUN | Year: 2004 | pages: 8
Detection of damage to structures has recently received considerable attention from the viewpoint of maintenance
and safety assessment. In this respect, the vibration characteristics of buildings have been applied consistently to
obtain a damage index of the whole building, but it has not been established as a practical method until now. It
is reasoned that this is perhaps due to restrictions on the experiment, use of improper method, and lack of inspection
opportunity for the structures. In addition, in the case of large-scale structures such as buildings, many variables
to be considered for the analysis contribute to a large number of degrees of freedom, and this can also be
a considerable problem for the analysis. A practical method for the detection of structural damage using the first
natural frequency and mode shape of building is proposed in this paper. The effectiveness of the proposed method
is verified by numerical analysis and experimental tests. From the results, it is observed that the severity and location
of the damage can be estimated with a relatively small error by using modal properties of building.
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SHEAR WALL WITH OUTRIGGER TRUSSES ON WALL AND COLUMN FOUNDATIONS
Author: J. C. D. HOENDERKAMP | Size: 169 KB | Format:PDF | Quality:Unspecified | Publisher: J. C. D. HOENDERKAMP | Year: 2004 | pages: 15
A graphical method of analysis is presented for preliminary design of outrigger truss-braced high-rise shear wall
structures with non-fixed foundation conditions subject to horizontal loading. The method requires the calculation
of six structural parameters: bending stiffness for the shear wall, bending and racking shear stiffnesses for
the outrigger, an overall bending stiffness contribution from the exterior columns, and rotational stiffnesses for
the shear wall and column foundations.
The method of analysis employs a simple procedure for obtaining the optimum location of the outrigger up
the height of the structure and a rapid assessment of the influence of the individual structural elements on the
lateral deflections and bending moments of the high-rise structure. It is concluded that all six stiffnesses should
be included in the preliminary analysis of a proposed tall building structure as the optimum location of the outrigger
as well as the reductions in horizontal deformations and internal forces in the structure can be significantly
influenced by all the structural components.
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This paper presents results from an international research project devoted to evaluating the seismic performance
of a three-storey steel frame structure equipped with a friction-damping device (FDD) recently developed at the
Technical University of Denmark. Experimental results indicate that the FDD performed very well in reducing
the lateral storey drifts of the test frame. Numerical simulation of the seismic response of the primary and
friction-damped frame was also conducted. This paper also compares the predictions of the displacement demand
from the test results with those obtained by the capacity spectrum method.
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OPTIMIZED USE OF THE OUTRIGGER SYSTEM TO STIFFEN THE COUPLED SHEAR WALLS IN TALL BUILDINGS
Author: NAVAB ASSADI ZEIDABADI , KAMAL MIRTALAE AND BARZIN MOBASHER | Size: 250 KB | Format:PDF | Quality:Unspecified | Publisher: NAVAB ASSADI ZEIDABADI , KAMAL MIRTALAE1 AND BARZIN MOBASHER | Year: 2004 | pages: 19
Based on the conventional yet accurate continuum approach, a general analysis is presented for a pair of coupled
shear walls, stiffened by an outrigger and a heavy beam in an arbitrary position on the height. Subsequently, a
parametric study is presented to investigate the behavior of the structure. The optimum location of the outrigger
and the parameters affecting its position were also investigated. The results showed that the behavior of the structure
can be significantly influenced by the location of the outrigger. It was also indicated that in most ordinary
cases the best location of the structure to minimize top drift is somewhere between 0·4 to 0·6 of the height of the
structure. Though this method is not a substitute for the finite element method, it gives an initial simple solution
to determine the size and position of outrigger, stiffening beam and coupled shear walls in the preliminary design
stages.
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ON MODELLING OF TYPHOON-INDUCED NON-STATIONARY WIND SPEED FOR TALL BUILDINGS
Author: J. CHEN AND Y. L. XU | Size: 1.74 MB | Format:PDF | Quality:Unspecified | Publisher: J. CHEN AND Y. L. XU | Year: 2004 | pages: 19
Typhoon-induced wind around tall buildings may not be stationary because it is a large body of rotating air. A
new approach is thus proposed in this paper for characterizing typhoon-induced wind speed. Typhoon-induced
non-stationary wind speed is modelled as a deterministic time-varying mean wind speed component plus a zero
mean stationary fluctuating wind speed component. The time-varying mean wind speed is naturally extracted
from the measured wind speed time history using empirical mode decomposition (EMD). Wind characteristics
described in the traditional approach based on a stationary wind model are redefined and extended in the nonstationary
wind model. The new approach is then applied to wind data measured at the Di Wang building during
Typhoon York. The results show that most of recorded wind samples are non-stationary but they can be decomposed
into a time-varying mean wind speed component plus a well-behaved zero mean fluctuating wind speed
component admitted as a stationary random process with Gaussian distribution. Other wind characteristics such
as probability distribution of fluctuating wind speed, turbulence intensity, gust factor, and wind spectrum obtained
by the new approach seem to be more realistic than those gained by the traditional approach.
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