Wind Directionality Factors for Nonhurricane and Hurricane-Prone Regions
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VIEW THE REPLYPublication: Journal of Structural Engineering
Volume 141, Issue 8
Abstract
The wind directionality factor, , is a nondimensional quantity smaller than unity that reflects the fact that the climatologically and aerodynamically or dynamically most unfavorable wind directions typically do not coincide. The ASCE 7-10 standard specifies for buildings a directionality factor , although no justification appears to have been adduced for this value in the literature. This paper presents a more informed discussion of this topic by the engineering and codification communities. The results of this work show that the directional factor varies as a function of type of wind storm, geographical location within an area with a given type of wind climate, type of wind effect (e.g., local pressures, internal forces in members of wind force resisting systems, global shear or torsion), and position of the wind effect being considered in the structure. These results suggest that, in most if not all cases, the dependence of the directionality factor on mean recurrence interval of wind effects is weak, and they confirm a recent finding that values are larger for hurricane-prone than for nonhurricane regions. For pressures at individual points on building envelopes, the value is typically found to be adequate for hurricane-prone regions and conservative for nonhurricane regions. For internal forces in wind force resisting systems (e.g., frames), the value is typically adequate for nonhurricane regions while is required for hurricane-prone regions, in spite of its conservatism in some situations. Finally, for global effects, such as building base shears and global building torsion, the values and are appropriate for nonhurricane and hurricane-prone regions, respectively.
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Acknowledgments
The writers thank F. T. Lombardo for providing the wind speed data sets used in this work.
Disclaimer
(1) The policy of the NIST is to use the International System of Units in its technical communications. In this document however, works of authors outside NIST are cited which describe measurements in certain non-SI units. Thus, it is more practical to include the non-SI unit measurements from these references. (2) Certain trade names or company products or procedures may be mentioned in the text to specify adequately the experimental procedure or equipment used. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products or procedures are the best available for the purpose.
References
ASCE. (2010). “Minimum design loads for buildings and other structures.”, Reston, VA.
Davenport, A. G. (1977). “The prediction of risk under wind loading.” Proc., Int. Conf. on Structural Safety and Reliability, G. I. Schueller, ed., Munich Technical Univ., Munich, Germany.
Ellingwood, B., Galambos, T., McGregor, J. G., and Cornell, C. A. (1980). “Development of a probability-based load criterion for American National Standard A58.”, Washington, DC, 577.
Ellingwood, B. R., and Tekie, P. B. (1999). “Wind load statistics for probability-based structural design.” J. Struct. Eng., 453–463.
Gabbai, R. D., and Simiu, E. (2014). “Evaluation of mean recurrence intervals of wind effects for tall building design.” J. Struct. Eng., 040130371–040130376.
Ho, T. C. E., Surry, D., and Morrish, D. P. (2003). “NIST/TTU cooperative agreement—Windstorm mitigation initiative: Wind tunnel experiments on generic low buildings, BLWT-SS20-2003.” 〈http://fris2.nist.gov/winddata/uwo-data/blwt-ss20-2003.pdf〉 (Sep. 3, 2014).
Isyumov, N., Ho, E., and Case, P. (2013). “Influence of wind directionality on wind loads and responses.” Proc., 12th Americas Conf. on Wind Engineering, D. A. Reed and A. Jain, eds., Univ. of Washington, Seattle.
Laboy-Rodriguez, S. T., Gurley, K. R., and Masters, F. J. (2013). “Revisiting the directionality factor in ASCE 7.” Proc., 12th Americas Conf. on Wind Engineering, D. A. Reed and A. Jain, eds., Univ. of Washington, Seattle.
Lombardo, F. T. (2013). “Standardized extreme wind speed database for the United States.” 〈http://www.itl.nist.gov/div898/winds/NIST_TN/nist_tn.htm〉 (Sep. 3, 2014).
Lombardo, F. T., Main, J. A., and Simiu, E. (2009). “Automated extraction and classification of thunderstorm and non-thunderstorm wind data for extreme-value analysis.” J. Wind Eng. Ind. Aerodyn., 97(3–4), 120–131.
Main, J. A., and Fritz, W. P. (2006). Database-assisted design for wind: Concepts, software, and examples for rigid and flexible buildings, National Institute of Standards and Technology, Technology Administration, U.S. Dept. of Commerce, Gaithersburg, MD, 〈http://www.itl.nist.gov/div898/winds/wind_pressure/wind_pressure.htm〉 (Sep. 3, 2014).
Sadek, F., and Simiu, E. (2002). “Peak non-gaussian wind effects for database-assisted low-rise building design.” J. Eng. Mech., 530–539.
Simiu, E. (2011). Design of buildings for wind: A guide for ASCE 7-10 standard users and designers of special structures, Wiley, Hoboken, NJ.
Yeo, D. (2011). “Database-assisted design for high-rise structures in mixed extreme wind climates.” 13th Int. Conf. on Wind Engineering, Dutch-Flemish Wind Engineering Association, Amsterdam, Netherlands.
Yeo, D. (2014). “Generation of large directional wind speed data sets for estimation of wind effects with long return periods.” J. Struct. Eng., 04014073.
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© 2014 American Society of Civil Engineers.
History
Received: Jan 2, 2014
Accepted: Aug 19, 2014
Published online: Sep 26, 2014
Discussion open until: Feb 26, 2015
Published in print: Aug 1, 2015
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