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CONTENTS
Volume 1, Number 3, September 1998
 

Abstract
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 assoicated with various zones of each roof and their parameters are provided. The established spectral parameters can be used to generate syntheic spectra adequate for the simulation of wind pressure fluctuations on building surfaces in a generic fashion

Key Words
building; low-rise; roofs; spectral density function; wind pressure.

Address
Faculty of Building, Architecture and Planning, FAGO, Technical University of Eindhoven, Postbus 513, 5600 MB Eindhoven , The Netherlands

Abstract
The high-rise supporting towers of long-span suspension and cable-stayed bridges commonly comprise a pair of slender prisms of roughly square cross-section with a center-to-centre spacing of from perhaps 2 to 6 widths and connected by one or more cross-ties. The tower columns may have a constant spacing as common for suspension bridges or the spacing may reduce towards the top of the tower. The present paper is concerned with the aerodynamics of such towers and describes an experimental investigation of the overall aerodynamic forces acting on a pair of square cylinders in two-dimensional flow. Wind tunnel pressure measurements were carried out in smooth flow and with a longitudinal intensity of turbulence 0.10. Different angles of attack were considered between 0 degree and 90 degree, and separations between the two columns from twice to 13 times the side width of the column. The mean values of the overall forces proved to be related to the bias introduced in the flow by the interaction between the two cylinders; the overall rms forces are related to the level of coherence between the shedding-induced forces on the two cylinders and to their phase. Plots showing the variation of the force coefficients and Strouhal number as a function of the separation, together with the force coefficients spectra and lift cross-correlation functions are presented in the paper.rn

Key Words
bluff body aerodynamics; aerodynamic interference; wind tunnel testing; aerodynamic forces; bridge towers.

Address
The Boundary Layer Wind Tunnel Laboratory, Faculty of Engineering Science, The University of Western Ontario, London, Ontario, N6A 5B9, Canada

Abstract
The paper deals with numerical analysis of interference galloping of two elastically supported circular cylinders of equal diameters. The basis of the analysis is quasi-steady model of this phenomenon. The model assumes that both cylinders participate in process of interference galloping and they have two degrees of freedom. The movement of the cylinders is written as a set of four nonlinear differential equations. On the basis of numerical solutions of this equations the authors evaluate the correctness of this quasi-steady model. Then they estimate the dependence of a critical reduced velocity on the Scruton number, turbulence intensity and arrangements of the cylinder.

Key Words
aerodynamic interference; a cylinder, interference galloping; the quasi-steady theory; the numerical analysis.

Address
Department of Structural Mechanics, Faculty of Civil and Sanitary Engieering, Lublin Technical University, ul Nadbystrzycka 40, 20-618 Lublin, Poland

Abstract
Second-order moments of considerable magnitude arise in tall and slender RC chimneys towers subject to along-wind loading, on account of eccentricities in the distributed self-weight of the tower in the deflected profile. An accurate solution to this problem of geometric nonlinearity is rendered difficult by the uncertainties in estimating the flexural rigidity of the tower, due to variable cracking of concrete and the

Key Words
reinforced concrete; chimneys; towers; moment-curvature relationship; tension stiffening effect; second-order moment; geometric nonlinearity; along-wind response.

Address
Department of Civil Engineering, Indian Institute of Technology, Madras 600 036, India

Abstract
This paper uses the numerical simulation to investigate the interference effect of 3-D turbulent flow around two high rise buildings in proximity at the different relative heights, gaps, and wind velocities. The computer program used to carry out the simulation is based on the control volumne method and the SIMPLEST algorithm. The k-e model was used to simulate turbulence effects. Since the contracted flow between two adjacent buildings enhances the strength of vortex shedding from the object building, the pressure coefficient on each side wall of the object building is generally increased by the presence of apposed building. The effect is increased as the relative height or the gap between the two buildings decreases. The velocity on the vertical center line between two buildings is about 1.4 to 1.5 times the upstream wind velocity.

Key Words
high rise buildings; SIMPLEST; k-e model.

Address
Department of Mechanical Engineering, Feng-Chia University, Taichung, 40725, Taiwan, R.O.C.


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