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Assessment of vertical wind loads on lattice framework with application to thunderstorm winds

  • Mara, T.G. (The Boundary Layer Wind Tunnel Laboratory, The University of Western Ontario) ;
  • Galsworthy, J.K. (Rowan Williams Davies & Irwin Inc.) ;
  • Savory, E. (Department of Mechanical and Materials Engineering, The University of Western Ontario)
  • Received : 2009.07.21
  • Accepted : 2010.03.03
  • Published : 2010.09.25

Abstract

The focus of this article is on the assessment of vertical wind vector components and their aerodynamic impact on lattice framework, specifically two distinct sections of a guyed transmission tower. Thunderstorm winds, notably very localized events such as convective downdrafts (including downbursts) and tornadoes, result in a different load on a tower's structural system in terms of magnitude and spatial distribution when compared to horizontal synoptic winds. Findings of previous model-scale experiments are outlined and their results considered for the development of a testing rig that allows for rotation about multiple body axes through a series of wind tunnel tests. Experimental results for the wind loads on two unique experimental models are presented and the difference in behaviour discussed. For a model cross arm with a solidity ratio of approximately 30%, the drag load was increased by 14% when at a pitch angle of $20^{\circ}$. Although the effects of rotation about the vertical body axis, or the traditional 'angle of attack', are recognized by design codes as being significant, provisions for vertical winds are absent from each set of wind loading specifications examined. The inclusion of a factor to relate winds with a vertical component to the horizontal speed is evaluated as a vertical wind factor applicable to load calculations. Member complexity and asymmetric geometry often complicate the use of lattice wind loading provisions, which is a challenge that extends to future studies and codification. Nevertheless, the present work is intended to establish a basis for such studies.

References

  1. American Society of Civil Engineers (ASCE) (1991), Guidelines for electrical transmission line structural loading, ASCE Manuals and Reports on Engineering Practice, No. 74, New York, USA.
  2. American National Standards Institute (1982), Minimum Design Loads for Buildings and Other Structures, ANSI Standard A58.1-1982, New York, USA.
  3. ANSI/TIA (2006), Structural Standard for Antenna Supporting Structures and Antennas, ANSI Standard TIA-222-G, Telecommunications Industry Association, Arlington, VA, USA.
  4. Bayar, D.C. (1986), "Drag coefficients of lattice structures", J. Struct. Eng.-ASCE, 112(2), 417-430. https://doi.org/10.1061/(ASCE)0733-9445(1986)112:2(417)
  5. British Standards Institution (1972), British Standard Code of Practice CP3: Code of Basic Data for the Design of Buildings, Chapter V: Loading: Part 2: Wind loads, London, UK.
  6. Carril Jr., C.F., Isyumov, N. and Brasil, R.M.L.R.F. (2003), "Experimental study of the wind forces on rectangular latticed communication towers with antennas", J. Wind Eng. Ind. Aerod., 91(8), 1007-1022. https://doi.org/10.1016/S0167-6105(03)00049-7
  7. Chay, M.T., Albermani, F. and Wilson, R. (2006), "Numerical and analytical simulation of downburst wind loads", Eng. Struct., 28(2), 240-254. https://doi.org/10.1016/j.engstruct.2005.07.007
  8. Chen, L. and Letchford, C.W. (2004), "Parametric study on the along-wind response of the CAARC building to downbursts in the time domain", J. Wind Eng. Ind. Aerod., 92(9), 703-724. https://doi.org/10.1016/j.jweia.2004.03.001
  9. Dempsey, D. and White, H.B. (1996), "The cause of most transmission structure outages in the world is high intensity winds", T&D World Mag., 48(6), 32-42.
  10. Flachsbart, O. (1932), "Winddruck auf vollwandige bauwerke und gitterfachwerke", Int. Assoc. Bridge Struct. Eng., 1, 153-172.
  11. Flachsbart, O. and Winter, H. (1934), "Modellversuche ueber die belastung von Gitterfachwerken durch Windkrafte", Der Stahblau, Translated by Scandia Corporation, Report No. AFSWP-464.
  12. Fujita, T.T. (1985), The Downburst: Microburst and Macroburst, SMRP Research Paper 210, Department of Geophysical Sciences, University of Chicago.
  13. Fujita, T.T. (1990), "Downbursts: Meteorological features and wind field characteristics", J. Wind Eng. Ind. Aerod., 36(1), 75-86. https://doi.org/10.1016/0167-6105(90)90294-M
  14. Georgiou, P.N. and Vickery, B.J. (1979), "Wind loads on building frames", Proceedings of the 5th International Conference of Wind Engineering, Fort Collins, CO, USA, July.
  15. Hangan, H.M., Roberts, D., Xu, Z. and Kim, J. (2003), "Downburst simulations. Experimental and numerical challenges", Proceedings of the 11th International Conference on Wind Engineering, Lubbock, TX, USA, June.
  16. Holmes, J.D. and Oliver, S.E. (2000), "An empirical model of a downburst", Eng. Struct., 22(9), 1167-1172. https://doi.org/10.1016/S0141-0296(99)00058-9
  17. Holmes, J.D., Hangan, H.M., Schroeder, J.L., Letchford, C.W. and Orwig, K.D. (2008), "A forensic study of the Lubbock-Reese downdraft of 2002", Wind Struct., 11(2), 137-152. https://doi.org/10.12989/was.2008.11.2.137
  18. Jacobs, B.E.A. (1978), "Determination of shielding factors for multiple frame structures", Proceedings of the 3rd Colloquium on Wind Engineering, Aachen, Germany.
  19. Kim, J. and Hangan, H.M. (2007), "Numerical simulation of impinging jets with application to downbursts", J. Wind Eng. Ind. Aerod., 95(4), 279-298. https://doi.org/10.1016/j.jweia.2006.07.002
  20. Kim, J., Hangan, H.M. and Ho, T.C.E. (2007), "Downburst versus boundary layer induced wind loads for tall buildings", Wind Struct., 10(5), 481-494. https://doi.org/10.12989/was.2007.10.5.481
  21. Letchford, C.W., Mans, C. and Chay, M.T. (2002), "Thunderstorms – their importance in wind engineering (a case for the next generation wind tunnel)", J. Wind Eng. Ind. Aerod., 90(12-15), 1415-1433. https://doi.org/10.1016/S0167-6105(02)00262-3
  22. Li, C.Q. (2000), "A stochastic model of severe thunderstorms for transmission line design", Probabilist. Eng. Mech., 15(4), 359-364. https://doi.org/10.1016/S0266-8920(99)00037-5
  23. Lin, W.E., Orf, L.G., Savory, E. and Novacco, C. (2007), "Proposed large-scale modelling of the transient features of a downburst outflow", Wind Struct., 10(4), 315-346. https://doi.org/10.12989/was.2007.10.4.315
  24. Mason, M.S., Wood, G.S. and Fletcher, D.F. (2009), "Influence of tilt and surface roughness on the outflow wind field of an impinging jet", Wind Struct., 12(3), 179-204. https://doi.org/10.12989/was.2009.12.3.179
  25. McCarthy, P. and Melsness, M. (1996), Severe weather elements associated with September 5th, 1996 hydro tower failures near Grosse Isle, Manitoba, Canada, Manitoba Environmental Services Centre, Environment Canada.
  26. National Research Council Canada (1977), National Building Code of Canada 1977, Canadian Commission on Building and Fire Codes.
  27. National Research Council Canada (2005), National Building Code of Canada 2005, Canadian Commission on Building and Fire Codes.
  28. Nolasco, J.F. (1996), Analysis of recent transmission line failures, CIGRE WG 22.06: Review of IEC 826: Loading and Strength of Overhead Lines, CIGRE, 87-98.
  29. Oliver, S.E., Moriarty, W.W. and Holmes, J.D. (2000), "A risk model for design of transmission line systems against thunderstorm downburst winds", Eng. Struct., 22(9), 1173-1179. https://doi.org/10.1016/S0141-0296(99)00057-7
  30. Orwig, K.D. and Schroeder, J.L. (2007), "Near-surface wind characteristics of extreme thunderstorm outflows", J. Wind Eng. Ind. Aerod., 95(7), 565-584. https://doi.org/10.1016/j.jweia.2006.12.002
  31. Pagon, W.W. (1958), "Wind forces on structures-plate girders and trusses", J. Struct. Div.-ASCE, 84(ST-4), 1711-1-1711-27.
  32. Ponte Jr., J. and Riera, J.D. (2007), "Wind velocity field during thunderstorms", Wind Struct., 10(3), 287-300. https://doi.org/10.12989/was.2007.10.3.287
  33. Savory, E., Hangan, H.M., El Damatty, A.A., Galsworthy, J. and Miller, C. (2008), "Modeling and prediction of failure of transmission lines due to high intensity winds", Proceedings of the 2008 ASCE Structures Congress, Vancouver, BC, Canada, April.
  34. Savory, E., Parke, G.A.R., Zeinoddini, M., Toy, N. and Disney, P. (2001), "Modelling of tornado and microburstinduced wind loading and failure of a lattice transmission tower", Eng. Struct., 23(4), 365-375. https://doi.org/10.1016/S0141-0296(00)00045-6
  35. Shehata, A.Y. and El Damatty, A.A. (2007), "Behaviour of guyed transmission line structures under downburst wind loading", Wind Struct., 10(3), 249-268. https://doi.org/10.12989/was.2007.10.3.249
  36. Shehata, A.Y. and El Damatty, A.A. (2008), "Failure analysis of a transmission tower during a microburst", Wind Struct., 11(3), 193-208. https://doi.org/10.12989/was.2008.11.3.193
  37. Standards Australia (2002), Structural design actions. Part 2: Wind actions. Australian/New Zealand Standard, AS/NZS 1170.2:2002.
  38. Standards Australia (2003), Guidelines for design and maintenance of overhead lines C(b)1-2003, Electrical Supply Association of Australia.
  39. Sykes, D.M. (1981), "Lattice frames in turbulent airflow", J. Wind Eng. Ind. Aerod., 7(2), 203-214. https://doi.org/10.1016/0167-6105(81)90038-6
  40. Whitbread, R.E. (1979), "The influence of shielding on the wind forces experienced by arrays of lattice frames", Proceedings of the 5th International Conference on Wind Engineering, Fort Collins, CO, USA, July.
  41. Wood, G.S., Kwok, K.C.S., Motteram, N.A. and Fletcher, D.F. (2001), "Physical and numerical modelling of thunderstorm downbursts", J. Wind Eng. Ind. Aerod., 89(6), 535-552. https://doi.org/10.1016/S0167-6105(00)00090-8

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