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CONTENTS
Volume 14, Number 1, January 2011
 

Abstract
Open frame structures, such as those commonly found in industrial process facilities, are often densely occupied with process related equipment. This paper presents a method for estimating wind loads for high-solidity open frame structures that differs from current approaches, which accumulate wind load contributions from various individual structure components. The method considers the structure as a porous block of arbitrary plan dimension that is subject to wind from any direction. The proposed method compares favorably with wind tunnel test results for similar structures. The possibility of defining an upper bound force coefficient is also discussed.

Key Words
open frame structures; wind load; porous structure; force coefficient.

Address
Samuel D. Amoroso: ENGENSUS,LLC, 9191 Siegen Lane, Building 6, Suite A, Baton Rouge, LA 70810, USA
Marc L. Levitan: Civil and Environmental Engineering Department, Louisiana State University,3418 Patrick F. Taylor Hall, Baton Rouge, LA 70803, USA

Abstract
Three wind-tunnel simulations of the atmospheric boundary layer (ABL) flow in suburban country exposure were generated for length scale factors 1:400, 1:250 and 1:220 to investigate scale effects in wind-tunnel simulations of the suburban ABL, to address recommended wind characteristics for suburban exposures reported in international standards, and to test redesigned experimental hardware.Investigated parameters are mean velocity, turbulence intensity, turbulent Reynolds shear stress, integral length scale of turbulence and power spectral density of velocity fluctuations. Experimental results indicate it is possible to reproduce suburban natural winds in the wind tunnel at different length scales without significant influence of the simulation length scale on airflow characteristics. However, in the wind tunnel it was not possible to reproduce two characteristic phenomena observed in full-scale: dependence of integral length scales on reference wind velocity and a linear increase in integral length scales with height. Furthermore, in international standards there is a considerable scatter of recommended values for suburban wind characteristics. In particular, recommended integral length scales in ESDU 85020 (1985) are significantly larger than in other international standards. Truncated vortex generators applied in this study proved to be successful in part-depth suburban ABL wind-tunnel simulation that yield a novel methodology in studies on wind effects on structures and air pollution dispersion.

Key Words
atmospheric boundary layer; atmospheric turbulence; suburban country exposure; wind-tunnel experiments; experimental hardware; scaling issues; international standards and codes.

Address
Hrvoje Kozmar: Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lu i a 5, HR-10000 Zagreb, Croatia

Abstract
Spherical object in wind is a common scenario in daily life and engineering practice. The main challenge in understanding the aerodynamics in turbulent wind lies in the multi-aspect of turbulence. This paper presents a wind tunnel study, which focuses on the role of turbulence integral length scale on the drag of a sphere. Particular turbulent flow conditions were achieved via the proper combination of wind speed, orifice perforated plate, sphere diameter (D) and distance downstream from the plate. The drag was measured in turbulent flow with and turbulence intensity Tu up to 6.3%. Our results confirmed the general trends of decreasing drag coefficient and critical Reynolds number with increasing turbulence intensity. More interestingly, the unique role of the relative integral length scale has been revealed. Over the range of conditions studied, an integral length of approximately 65% the sphere diameter is most effective in reducing the drag.

Key Words
sphere; orifice perforated plate; turbulence; drag coefficient; integral length scale.

Address
Niloofar Moradian: Department of Mechanical, Automotive and Materials Engineering, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada N9B 3P4
David S-K. Ting: Department of Mechanical, Automotive and Materials Engineering, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada N9B 3P4
Shaohong Cheng: Department of Civil and Environmental Engineering, University of Windsor,401 Sunset Avenue, Windsor, ON, Canada N9B 3P4

Abstract
This study investigates the design criteria required for wind barriers to protect vehicles running on an expressway under a high side wind. At the first stage of this study, the lateral deviations of vehicles in crosswinds were computed from the commercial software, CarSim and TruckSim, and the critical wind speeds for a car accident were then evaluated from a predefined car accident index. The critical wind speeds for driving stability were found to be 35 m/s for a small passenger car, yet 30 m/s for a truck and a bus. From the wind tunnel tests, the minimum height of a wind barrier required to reduce the wind speed by 50% was found to be 12.5% of the road width. In the case of parallel bridges, the placement of two edge wind barriers plus one wind barrier at center was recommended for a separation distance larger than 20 m (four lanes) and 10 m (six lanes) respectively, otherwise two wind barriers were recommended.

Key Words
wind barrier; shelter effect; driving stability; parallel bridge; vehicle protection; wind tunnel test.

Address
Soon-Duck Kwon:KOCED Wind Tunnel Center, Department of Civil Engineering, Chonbuk National University,Chonju, Chonbuk, 561-756, Korea
Dong Hyawn Ki: Department of Coastal Construction Engineering, Kunsan National University,Kunsan, Chonbuk, 573-701, Korea
Seung Ho Lee: KOCED Wind Tunnel Center, Department of Civil Engineering, Chonbuk National University, Chonju, Chonbuk, 561-756, Korea
Ho Sung Song : KOCED Wind Tunnel Center, Department of Civil Engineering, Chonbuk National University, Chonju, Chonbuk, 561-756, Korea

Abstract
This study presents a decision making process for installation of wind barrier which is used to reduce the wind speed applied to running vehicles on expressway. To determine whether it is needed to install wind barrier or not, cost and benefit from wind barrier are calculated during lifetime. In obtaining car accidental risk, probabilistic distribution of wind speed, daily traffic volume, mixture ratio in the volume, and duration time for wind speed range are considered. It is recommended to install wind barrier if benefit from the barrier installation exceed construction cost. In the numerical examples, case studies were shown for risk and benefit calculation and main risky regions on Korean highway were all evaluated to identify the number of installation sites.

Key Words
wind barrier; driving stability; side wind; car accident risk.

Address
Dong Hyawn Kim: 1Department of Coastal Construction Engineering, Kunsan National University, Kunsan, Chonbuk, 573-701, Korea
Soon-Duck Kwon: Department of Civil Engineering, Chonbuk National University, Chonju, Chonbuk, 561-756, Korea
Il Keun Lee: Expressway & Transportation Research Institute, Korea Expressway Corporation,Hwaseong, Gyeonggi, 445-812, Korea
Byung Wan Jo: Department of Civil and Environmental Engineering, Hanyang University,Seongdong, Seoul, 426-791, Korea

Abstract
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Key Words


Address
M.A. Goudarzi: Technical Department, Lorestan University, Khorramabad, Iran
S.R. Sabbagh-Yazdi: Civil Engineering Department, K.N.Toosi University of Technology,No.1346 Valiasr Street, 19697, Tehran, Iran


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