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(12 03-13)--wind effects


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(12 03-13)--wind effects

  1. 1. Wind effects on buildingsRajesh Kumar,Chanchal SonkarM.Tech., 1st year
  2. 2. OUTLINE Introduction Necessity Experimental setup Analytical study Graphical study Conclusion
  3. 3. Introduction Types of loads-(1). Dead load - Relatively constant over time (IS:875-part #1)(2). Imposed load –Temporary of short duration(IS:875-part #2)
  4. 4. Contd…(3). Environmental loads- Wind, rain, snow, ice, seismic,ponding etc.Side WallLeeward wallWindward wallRoofWind
  5. 5. NecessityIn the past, predicting the probable behavior of building componentsunder extreme winds has been difficult.Of all the environmental loads on buildings and structures, wind load isperhaps one of the most damaging
  6. 6. Contd… Scientists classify wind intensity and damage potential differently forhurricanes, tornados, and general wind storms.Types of storms -(1). Wind storms(2). Dust Storm(3). Sand Storm(4). Cyclones (South Pacific and Indian Ocean )(5). Hurricane (Atlantic and Northeast Pacific)(6). Typhoon (Northwest Pacific )etc. Follows IS:875 (Part # 3)
  7. 7. Experimental setup Wind load on overhangs in a low gable building in presence of freestanding wall. Building model was made on a geometry scale of 1:25 and a study wasconducted in an open circuit wind tunnel. Plan dimension 280mmx156mm and wall height 156mmwith roof slope 25 degrees, with an overhang eaves lengthof and 60mm free standing wall of height 66mm. Effects on pressure variation have been studied on both upper and lowersides of the overhang.
  8. 8. Contd…Free Standing wall(Boundary wall)280 mm=LOverhang wallFig. 2: Lay out of pressure taps in overhang
  9. 9. Contd…Source:
  10. 10. Analytical study Wind pressure measured on the roof of building models areexpressed in the form of a non dimensional pressure coefficientdefined as –Cp(i) = 2( Pi – Po)/ρU2Instantaneous surfacepressure Static (ambient, atmospheric)reference pressureAir densityMean velocitymeasured Mean Value = (Cp(1) + Cp(2) + Cp(3)+……..)/NTotal No. Of samples
  11. 11. Contd…Cp(min) =Min. of Cp(i) ; Cp(max) = Max. of Cp(i)
  12. 12. Graphical study Individual local pressure coefficients on eaves at various zones(1).For mean pressure coefficients-At upper surface(3>4>1>2)At lower surface
  13. 13. Contd…(2).For maximum pressure coefficients-At upper surface(3>1>4>2)At lower surface
  14. 14. Conclusions Commonly used roof angle of 25o was considered, andcorner, edge and center load on overhangs have been evaluated Net peak upward pressure shows maximum positive value in thepresence of free standing wall, located at a distance of 3h.
  15. 15. References Stathopoulos, T., Luchian, H. (1994) .Wind-induced forces on eaves of lowbuilding. J. wind Eng. Ind. Aerodynamic, vol 52, pp 249-261. Stathopoulos, T., (1981) .Wind load on eaves of low buildings., J. Struct.Div., ASCE, 107, ST10, Proc. Paper 16543: 1921-1934. Journal of Wind & Engineering, Vol. 5, No. 1, Jan 2008, pp. 39-46“Alok David John, Ajay Gairola, Prem Krishna”(Indian Institute of Technology, Roorkee )