Calculate Wind Pressure due to Hurricanes

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Clarissa Lewis
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1 Calculate Wind Pressure due to Hurricanes ASCE 7-05 Method 2 Importance Factor ASCE 7-05 Sectoin Residential building are Category I When V > 00 When V < 00 I =.0 Gust Effect Factor ASCE 7-05 Section G = I z = c 33 z +.7g Q I z Q +.7 g v I z 6 Iz is the turbulence at height z z = 0.6 h z min = 5ft for building with h < or eual to z min, z shall be taken as z min c = 0.20 g Q = 3.4 g v = 3.4 Q = B + h L z 0.63 B = the horizontal dimension of building measure normal to wind direction, in ft h = mean roof height of a building or height of other structure, except that eave height shall be used for the roof angle θ of less than or eual to 0 deg, in ft L z = l l = 500ft ε = 5.0 z 33 ε

2 Exposure Category, Kz or Kh, ASCE 7-05 Section From Table 6-3 K h := "0-5" Column 0 is for height above ground level, z Column is for Exposure C, cases & 2 α z K z_5 = 2.0 For 5 ft < z < z.g z g 2 α 5 K z_ = 2.0 For z < 5 ft z g z g = 900ft 2 α = 9.5 Topographic Factor, Kzt, ASCE 7-05 Section K zt = + K K 2 K 3 K zt = Assuming no hills or escarpment Enclosure Classification, ASCE 7-05 Section z = K z K zt K d V 2 I Wind Directionality Factor, Kd, ASCE 7-05 Section K d = 0.85 Used when using ASD or LRFD for building Design Internal pressure Coefficients GCpi, ASCE 7-05 Section GC pi = 0.8 GC pi = 0.8 Assuming an Enclosed Building Two cases shall be considered to determine the critical load

3 External Pressure Coefficients Cp, GCpf or Force Coefficients Cf, ASCE 7-05 Section or GC pf = 0.69 This value is the most conservative value and corresponds with the building face that will experience a pressure acting on that face Low-Rise Building, ASCE 7-05 Section p = h GC pf ( GC pi ) h is the velocity pressure at the roof height It is assumed for buildings under 30 ft that the wind load will act uniformly over the lenght of the structure Calculations Hurricane Categories Changeable Values h := 30ft h includes the roof height home_size := 2405 length := 36ft width := home_size length B := width B = ft h 0ft roof_angle := atan roof_angle = deg 0.5 length Changeable Parameters based on Assumptions noted Above c := 0.20 K h := 0.98 ε := K 5 zt := l := 500ft K d := 0.85 g Q := 3.4 GC p := 0.8 g v := 3.4 GC p2 := 0.8 z g := 900ft GC pf := 0.69 α := 9.5 Hurricane Parameters

4 V _min := 75 V 4_min := 3 V _max := 95 V 4_max := 55 V 2_min := 96 V 5_min := 56 V 2_max := 0 V 3_min := V 3_max := 30 Values based on Changeable Parameters z := 0.6 h z min := 5ft z control := max z, z min z control = 8 ft z := z control ft 6 33 I z := c z I z = 0.22 ε z L z := l 33 L z = ft Q := Q = B + h L z +.7g Q I z Q G := G = g v I z α zft fz := 2.0 if z > 5 z g K z := fz 2 α 5ft 2.0 if z 5 z g 2 K z = 0.882

5 Min pressure for Category Hurricane V := V _min f( V) := if V if V > 00 I:= I = f( V) si V 2 2 si = 4.4 s := si psf s = 4.4 psf z := s K z K zt K d I z = psf p := z GC pf GC p pressure category min := max p, p 2 pressure category min = lbf Max pressure for Category Hurricane V := V _max f( V) := if V if V > 00 I = fv si V 2 2 si = s := si psf s = psf z := s K z K zt K d I z = psf p := z GC pf GC p

6 pressure category max := max p, p 2 pressure category max = 5.07 lbf Min pressure for Category 2 Hurricane V := V 2_min f( V) := if V if V > 00 I = fv si V 2 2 si = s := si psf s = psf z := s K z K zt K d I z = 7.69 psf p := z GC pf GC p pressure category_2_min := max p, p 2 pressure category_2_min = 5.39 lbf Max pressure for Category 2 Hurricane V := V 2_max f( V) := if V if V > 00 fv si V 2 2 si = s := si psf s = psf z := s K z K zt K d I z = psf

7 p := z GC pf GC p pressure category_2_max := max p, p 2 pressure category_2_max = lbf Min pressure for Category 3 Hurricane V := V 3_min f( V) := if V if V > 00 fv si V 2 2 si = s := si psf s = psf z := s K z K zt K d I z = 8.2 psf p := z GC pf GC p pressure category_3_min := max p, p 2 pressure category_3_min = lbf Max pressure for Category 3 Hurricane V := V 3_max f( V) := if V if V > 00 fv si V 2 2 si = s := si psf s = psf

8 z := s K z K zt K d I z = psf p := z GC pf GC p pressure category_3_max := max p, p 2 pressure category_3_max = 2.73 lbf Min pressure for Category 4 Hurricane V := V 4_min f( V) := if V if V > 00 fv si V 2 2 si = s := si psf s = psf z := s K z K zt K d I z = psf p := z GC pf GC p pressure category_4_min := max p, p 2 pressure category_4_min = lbf Max pressure for Category 4 Hurricane V := V 4_max f( V) := if V if V > 00 fv si V 2 2 si = 6.504

9 s := si psf s = psf z := s K z K zt K d I z = psf p := z GC pf GC p pressure category_4_max := max p, p 2 pressure category_4_max = lbf Min pressure for Category 5 Hurricane V := V 5_min f( V) := if V if V > 00 fv si V 2 2 si = 62.3 s := si psf s = 62.3 psf z := s K z K zt K d I z = psf p := z GC pf GC p pressure category_5_min := max p, p 2 pressure category_5_min = lbf Summary of Pressure Due to Hurricane Winds pressure category min = lbf pressure category max = 5.07 lbf pressure category_2_min = 5.39 lbf pressure category_2_max = lbf

10 pressure category_3_min = lbf pressure category_3_max = 2.73 lbf pressure category_4_min = lbf pressure category_4_max = lbf pressure category_5_min = lbf pressure category min pressure category max pressure category_2_min pressure category_2_max Pressure := pressure category_3_min pressure category_3_max Pressure = pressure category_4_min pressure category_4_max pressure category_5_min 0 psf psf

Wind tunnel study on load combination including torsion for design of medium-rise buildings

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