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CONTENTS
Volume 6, Number 2, March 2003
 

Abstract
The paper presents the results of 1:50 geometrical scale laboratory modeling of wind-induced point pressure on the roof of the Texas Tech University (TTU) test building. The nominal (prevalent at the TTU site) wind and two bounding (low and high turbulence) flows were simulated in a boundary-layer wind tunnel at Colorado State University. The results showed significant increase in the pressure peak and standard deviation with an increase in the flow turbulence. It was concluded that the roof mid-plane pressure sensitivity to the turbulence intensity was the cause of the previously reported field-laboratory mismatch of the fluctuating pressure, for wind normal and 30 o -off normal to the building ridge. In addition, it was concluded that the cornering wind mismatch in the roof corner/ edge regions could not be solely attributed to the wind-azimuth-independent discrepancy between the turbulence intensity of the approach field and laboratory flows.

Key Words
wind tunnel modeling; wind turbulence, low-rise buildings; flat roofs; incident wind angles;suctions; pressure fluctuations.

Address
Wind Engineering and Fluids Laboratory, Department of Civil EngineeringrnColorado State University, Fort Collins, CO 80523, USArnDivision of Architecture, Kangwon National University, Chuncheon 200-701, Korea

Abstract
This paper describes a simple and practical approach through the application of Linear Stochastic Estimation (LSE) to reconstruct wind-induced pressure time series from the covariance matrix for structural load analyses on a low building roof. The main application of this work would be the reduction of the data storage requirements for the NIST aerodynamic database. The approach is based onrnthe assumption that a random pressure field can be estimated as a linear combination of some other known pressure time series by truncating nonlinear terms of a Taylor series expansion. Covariances between pressure time series to be simulated and reference time series are used to calculate the estimationrncoefficients. The performance using different LSE schemes with selected reference time series is demonstrated by the reconstruction of structural load time series in a corner bay for three typical wind directions. It is shown that LSE can simulate structural load time series accurately, given a handful of reference pressure taps (or even a single tap). The performance of LSE depends on the choice of the reference time series, which should be determined by considering the balance between the accuracy, data-storage requirements and the complexity of the approach. The approach should only be used for the determination of structural loads, since individual reconstructed pressure time series (for local loadrnanalyses) will have larger errors associated with them.

Key Words
aerodynamic database; data reduction; Linear Stochastic Estimation; low buildings; pressure time series; reconstruction; structural loads.

Address
The University of Western Ontario, London, Ontario, N6A 5B9, Canada

Abstract
An investigation into the effect of corner cuts on the Strouhal number of rectangular cylinders with various dimensional ratios and various angles of attack is described. The Strouhal number given as a function of corner cut size is obtained directly from the aerodynamic behavior of the body in a uniform flow through a series of wind-induced vibration tests. For a quick verification of the validity of the Strouhal numbers obtained in this way, they are compared with the approximated the Strouhal numbers based on Shiraishi

Key Words
Strouhal number; corner cut; angle of attack; wind tunnel experiment; rectangular cylinder.

Address
Department of Civil Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1 Kusong-dong, Yusong-gu, Taejon 305-701, KorearnDepartment of Civil Engineering and Geological Sciences, University of Notre Dame, USA

Abstract
This paper presents galloping analysis of multiple-degree-of-freedom (MDOF) structural roofsrnwith multiple orientations. Instead of using drag and lift coefficients and/or their combined coefficient inrntraditional galloping analysis for slender structures, this study uses wind pressure coefficients for windrnforce representation on each and every different orientation roof, facilitating the galloping analysis ofrnmultiple-orientation roof structures. In the study, influences of nonlinear aerodynamic forces are considered. An energy-based equivalent technique, together with the modal analysis, is used to solve the nonlinear MDOF vibration equations. The critical wind speed for galloping of roof structures is derived, which is then applied to galloping analysis of roofs of a stadium and a high-rise building in China. With the aid of various experimental results obtained in pertinent research, this study also shows that consideration of nonlinear aerodynamic forces in galloping analysis generally increases the critical wind speed, thus enhancing aerodynamic stability of structures.

Key Words
aerodynamic instability; galloping analysis; multiple-orientation roof structures; energy-based equivalent technique.

Address
Department of Engineering Mechanics and Technology and Center for CivilrnInfrastructure Systems Research, Tongji University, Shanghai 200092, ChinarnDivision of Engineering, Colorado School of Mines, Golden, Colorado 80401, USA

Abstract
On the basis of the first Lyapunov stability theory, this paper develops a dynamic stability criterion for elastic structural systems under arbitrary dynamic loads, and shows the stability criterion using energy variation. After the dynamic stability criterion is validated through a classic example, it is used for the dynamic stability investigation of practical guyed masts under random wind loads. The criterion is reliable, simple and of advantage for structures with large number of elements and nodes. The slack guys and internal resonance between guys and mast are two main factors which induces the dynamic instability of guyed masts, at the same time, some dynamic stability characteristics of guyed masts are found.

Key Words
guyed masts; dynamic stability; random wind loads.

Address
Research Center of Spatial Structures, Shanghai Jiao Tong University, Shanghai, 200030, P. R .ChinarnSchool of Civil Engineering, Tongji University, Shanghai, 200092, P. R. China

Abstract
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Key Words
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Address
Anemos Associates Ltd, 14 The Chestnuts, Hemel Hempstead, HP3 0DZ, U.K.rnUniversity of Birmingham, School of Civil Engineering, University of Birmingham,rnEdgbaston, Birmingham B15, 2TT, UKrnSilsoe Research Institute, Enviromental Group, Silsoe Reseaarch Institute, Wrest Park, Silsoe, Bedford MK45 4HS, UK


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