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CONTENTS
Volume 9, Number 5, September 2006
 

Abstract
It is well known that cylinder steel stacks are heavily impacted by vortex-induced vibration. However, the wind-induced vibration behaviors of tower-supported steel stacks are not clarified due to a lack of observation. We studied a stack

Key Words
tower-supported steel stack; strong wind observation; vortex-induced vibration; damping ratio.

Address
Tatsuya Susuki and Naoya Hanada; Civil Engineering Department, Kyushu Electric Power Co., Inc., Fukuoka 810-8720, JapanrnShin Homma; Steel Structures Headquarters, Hitachi Zosen Corporation, Osaka 550-0002, JapanrnJunji Maeda; Faculty of Human-Environment Studies, Kyushu University, Fukuoka 812-8581, Japan

Abstract
Unsteady 3D Reynolds Averaged Navier-Stokes (URANS) solver is used to simulate the turbulent flow past an isolated prismatic cylinder at Re = 37,400. The aspect ratio of height to base width of the body is 5. The turbulence closure is achieved through a non-linear k - e model. The applicability of this model to predict unsteady forces associated with this flow is examined. The study shows that the present URANS solver with standard wall functions predicts all the major unsteady phenomena showing closer agreement with experiment. This investigation concludes that URANS simulations with the non-linear k - e model as a turbulence closure provides a promising alternative to LES with view to study flows having complex features.

Key Words
bluff body; non-linear turbulence model; URANS.

Address
Department of Applied Mechanics, IIT Madras, Chennai-36, India

Abstract
A combination Aerodynamic/Atmospheric Boundary Layer (AABL) Wind and Gust Tunnel with a unique active gust generation capability has been developed for wind engineering and industrial aerodynamics applications. This facility is a cornerstone component of the Wind Simulation and Testing (WiST) Laboratory of the Department of Aerospace Engineering at Iowa State University (ISU). The AABL Wind and Gust tunnel is primarily a closed-circuit tunnel that can be also operated in open-return mode. It is designed to accommodate two test sections (2.44 m ? 1.83 m and 2.44 m ? 2.21 m) with a maximum wind speed capability of 53 m/s. The gust generator is capable of producing non-stationary gust magnitudes around 27% of the mean flow speed. This paper describes the motivation for developing this gust generator and the work related to its design and testing.

Key Words
active gust generation; non-stationary flow; wind tunnel; wind engineering.

Address
Fred L. Haan, Jr. and Partha P. Sarkar; Department of Aerospace Engineering, Iowa State University, 2271 Howe Hall, Rm. 1200, Ames, IA 50011, USArnNicholas J. Spencer-Berger; Dynamic Flight Loads, The Boeing Company, P.O. Box 3707 M/C: 03-KR, Seattle, WA 98124, USA

Abstract
This paper presents the wind characteristics of Typhoon Dujuan as measured at a 50 m guyed mast in Hong Kong. The basic wind speed, wind direction and turbulent intensity are studied at two measurement levels of the structure. The power spectral density of the typhoon is compared with the von Karman prediction, and the coherence between wind speeds at the two measurement levels is found to compare with Davenport

Key Words
guyed mast; nonlinear; typhoon; turbulence; correlation; power spectral density.

Address
S. S. Law; Civil and Structural Engineering Department, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, People\'s Republic of ChinarnJ. Q. Bu; Shijiazhuang Railway Institute, Shijiazhuang, Hebei, People\'s Republic of Chinarn X. Q. Zhu and S. L. Chan; Civil and Structural Engineering Department, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, People\'s Republic of China

Abstract
This paper presents the wind excited acceleration responses of a 50 m guyed mast under the action of Typhoon Dujuan. The response of the structure is reconstructed from using a full finite element model and an equivalent beam-column model. The wind load is modelled based on the measured wind speed and recommendations for high-rise structures. The nonlinear time response analysis is conducted using the Newton Raphson iteration procedure. Comparative studies on the measured and computed frequencies and acceleration responses show that the torsional vibration of the structure is significant particularly in the higher vibration modes after the first few bending modes. The equivalent model, in general, gives less accurate amplitude predictions than the full model because of the omission of torsional stiffness of the mast in the vibration analysis, but the root-mean-square value is close to the measured value in general with an error of less than 10%.

Key Words
wind load; guyed mast; nonlinear; mode shape; acceleration; finite element model; typhoon; eigenvalue; equivalent model.

Address
S. S. Law; Civil and Structural Engineering Department, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, People\'s Republic of ChinarnJ. Q. Bu; Shijiazhuang Railway Institute, Shijiazhuang, Hebei, People\' Republic of ChinarnX. Q. Zhu and S. L. Chan; Civil and Structural Engineering Department, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, People\'s Republic of China

Abstract
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Key Words
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Address
K. Abe, H. Kihara, A. Sakurai, E. Wada and K. Sato; Dept. of Aeronautics and Astronautics, Kyushu University, JapanrnM. Nishida; Dept. of Aerospace Systems Engineering, Sojo University, JapanrnY. Ohya; Research Institute for Applied Mechanics, Kyushu University, Japan


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