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  1. The wind shall be assumed to come from any horizontal direction.
  2. An importance factor I shall be determined in accordance with Section 1609.5.
  3. An exposure category shall be determined in accordance with Section 1609.4.
  4. A height and exposure adjustment coefficient, λ, shall be determined from Table 1609.6.2.1(4).
1609.6.2.1 Main Wind Force-Resisting System
Simplified design wind pressures, ps, for the main wind force-resisting systems represent the net pressures (sum of internal and external) to be applied to the horizontal and vertical projections of building surfaces as shown in Figure 1609.6.2.1. For the horizontal pressures (Zones A, B, C, D), ps is the combination of the windward and leeward net pressures. ps shall be determined from Equation 16-43).



where:

λ = Adjustments factor for building height and exposure from Table 1609.6.2.1(4).
I = Importance factor as defined in Section 1609.5.
Ps30 = Simplified design wind pressure for Exposure B, at h = 30 feet (9144 mm), and for I =1.0, from Table 1609.6.2.1(1).



For SI: 1 foot = 304.8 mm, 1 degree = 0.0 174 rad.

FIGURE 1609.6.2.1 MAIN WINDFORCE LOADING DIAGRAM
Notes:
1. Pressures are applied to the horizontal and vertical projections for Exposure B, at h = 30 feet, for I = 1.0. Adjust to other exposures and heights with adjustment factor λ.
2. The load patterns shown shall be applied to each corner of the building in turn as the reference corner.
3. For the design of the longitudinal MWFRS, use θ = 0°, and locate the Zone E/F, G/H boundary at the mid-length of the building.
4. Load Cases 1 and 2 must be checked for 25° <θ ≤ 45°. Load Case 2 at 25° is provided only for interpolation between 25° to 30°.
5. Plus and minus signs signify pressures acting toward and away from the projected surfaces, respectively.
6. For roof slopes other than those shown, linear interpolation is permitted.
7. The total horizontal load shall not be less than that determined by assuming PS = 0 in Zones B and D.
8. The zone pressures represent the following:
Horizontal pressure zones — Sum of the windward and leeward net (sum of internal and external) pressures on vertical projection of:

A — End zone of wall C — Interior zone of wall
B — End zone of roof D — Interior zone of roof
Vertical pressure zones — Net (sum of internal and external) pressures on horizontal projection of:
E — End zone of windward roof G — Interior zone of windward roof
F — End zone of leeward roof H — Interior zone of leeward roof

9. Where Zone E or G falls on a roof overhang on the windward side of the building, use EOH and GOH for the pressure on the horizontal projection of the overhang. Overhangs on the leeward and side edges shall have the basic zone pressure applied.
10. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4 percent of least horizontal dimension or 3 feet.
h: Mean roof height, in feet (meters), except that eave height shall be used for roof angles <10°.
θ: Angle of plane of roof from horizontal, in degrees.


TABLE 1609.6.2.1(1) SIMPLIFIED DESIGN WIND PRESSURE (MAIN WINDFORCE-RESISTING SYSTEM), ps30 (Exposure B at h = 30 feet with I = 1.0) (psf)

ROOF
ANGLE
(degrees)
ROOF
RISE IN
12
LOAD
CASE
ZONES
Horizontal Pressures Vertical Pressures Overhangs
A B C D E F G H EOH GOH
0 to 5° Flat 1 12.0 -6.0 8.0 -4.0 -14.0 -8.0 -10.0 -6.0 -20.0 -15.0
10° 2 1 22.0 -9.0 15.0 -5.0 -23.0 -14.0 -16.0 -11.0 -33.0 -26.0
15° 3 1 24.0 -8.0 16.0 -5.0 -23.0 -15.0 16.0 -12.0 -33.0 -26.0
20° 4 1 27.0 -7.0 18.0 -4.0 -23.0 -16.0 16.0 -12.0 -33.0 -26.0
25° 6 1
2
24.0
4.0
18.0
4.0
-11.0
-4.0
-15.0
-8.0
-8.0
-1.0
-12.0
-5.0
-20.0
-17.0
30° to
45°
7 to 12 1
2
22.0
22.0
15.0
15.0
17.0
17.0
12.0
12.0
2.0
9.0
-13.0
-7.0
1.0
7.0
-12.0
-5.0
-8.0
-4.0
-9.0
-9.0

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0174 rad, 1 mile per hour = 0.44 m/s, 1 pound per square foot = 47.9 N/m2.


TABLE 1609.6.2.1(2) NET DESIGN WIND PRESSURE (COMPONENT AND CLADDING), pnet30 (Exposure B at h = 30 feet with I = 1.0 and kzt = 1 and 98 mph 3 sec. gust basic wind speed) (psf)

ZONE EFFECTIVE
WIND AREA
PRESSURE/ SUCTION
Roof 0 to 7 degrees 1 10 7.0 -17.0
1 20 7.0 -16.0
1 50 6.0 -16.0
1 100 6.0 -15.0
2 10 7.0 -28.0
2 20 7.0 -25.0
2 50 6.0 -21.0
2 100 6.0 -18.0
3 10 7.0 -42.0
3 20 7.0 -35.0
3 50 6.0 -26.0
3 100 6.0 -18.0
Roof > 7 to 27 degrees 1 10 10.0 -15.0
1 20 9.0 -15.0
1 50 8.0 -14.0
1 100 7.0 -14.0
2 10 10.0 -27.0
2 20 9.0 -25.0
2 50 8.0 -22.0
2 100 7.0 -20.0
3 10 10.0 -39.0
3 20 9.0 -37.0
3 50 8.0 -33.0
3 100 7.0 -31.0


Roof > 27 to 45 degrees 1 10 15.0 -17.0
1 20 15.0 -16.0
1 50 14.0 -15.0
1 100 14.0 -14.0
2 10 15.0 -20.0
2 20 15.0 -19.0
2 50 14.0 -18.0
2 100 14.0 -17.0
3 10 15.0 -20.0
3 20 15.0 -19.0
3 50 14.0 -18.0
3 100 14.0 -17.0
ZONE EFFECTIVE
WIND AREA
PRESSURE/ SUCTION
Wall 4 10 17.0 -18.0
4 20 16.0 -18.0
4 50 15.0 -17.0
4 100 14.0 -16.0
4 500 13.0 -14.0
5 10 17.0 -22.0
5 20 16.0 -21.0
5 50 15.0 -19.0
5 100 14.0 -18.0
5 500 13.0 -14.0

For SI: 1 foot = 304.8 mm, 1 degree = 0.0 174 rad,
1 mile per hour = 0.44 m/s, 1 pound per square foot = 47.9 N/m2.
Note: For effective areas between those given above, the load is permitted to be interpolated, otherwise use the load associated with the lower effective area.


TABLE 1609.6.2.1(3) ROOF OVERHANG NET DESIGN WIND PRESSURE (COMPONENT AND CLADDING), pnet30 (Exposure B at h = 30 feet with Iw = 1.0 and 98 mph 3 sec. gust basic wind speed) (psf)

ZONE EFFECTIVE
WIND AREA
(sq. ft.)
PRESSURE/
SUCTION
Roof 0 to 7 degrees 2 10 -24.0
2 20 -24.0
2 50 -23.0
2 100 -23.0
3 10 -40.0
3 20 -31.0
3 50 -20.0
3 100 -12.0
Roof > 7 to 27 degrees 2 10 -31.0
2 20 -31.0
2 50 -31.0
2 100 -31.0
3 10 -52.0
3 20 -47.0
3 50 -41.0
3 100 -35.0
Roof > 27 to 45 degrees 2 10 -28.0
2 20 -28.0
2 50 -26.0
2 100 -26.0
3 10 -28.0
3 20 -28.0
3 50 -26.0
3 100 -26.0

For SI: 1 foot = 304.8 mm, 1 degree = 0.0174 rad,
1 mile per hour = 0.45 m/s, 1 pound per square foot = 47.9 N/m2.
Note: For effective areas between those given above, the load is permitted to be interpolated, otherwise use the load associated with the lower effective area.


TABLE 1609.6.2.1(4) ADJUSTMENT FACTOR FOR BUILDING HEIGHT AND EXPOSURE, (λ)

MEAN ROOF
HEIGHT
EXPOSURE
(feet) B C/C1 D
15 1.00 1.21 1.47
20 1.00 1.29 1.55
25 1.00 1.35 1.61
30 1.00 1.40 1.66
35 1.05 1.45 1.70
40 1.09 1.49 1.74
45 1.12 1.53 1.78
50 1.16 1.56 1.81
55 1.19 1.59 1.84
60 1.22 1.62 1.87

For SI: 1 foot = 304.8 mm.
a. All table values shall be adjusted for other exposures and heights by multiplying by the above coefficients.
1609.6.2.1.1 Minimum Pressures
The load effects of the design wind pressures from Section 1609.6.2.1 shall not be less than assuming the pressures, ps, for Zones A, B, C and D all equal to + 20 psf (0.96 kN/m2), while assuming Zones E, F, G, and H all equal to 0 psf.
1609.6.2.2 Components and Cladding
Net design wind pressures, pnet, for the components and cladding of buildings represent the net pressures (sum of internal and external) to be applied normal to each building surface as shown in Figure 1609.6.2.2. The net design wind pressure, pnet, shall be determined from Equation 16-44:



where:

λ = Adjustments factor for building height and exposure from Table 1609.6.2.1(4).
I = Importance factor as defined in Section 1609.5.
Pnet30 = Net design wind pressure for Exposure B, at h = 30 feet (9144 mm), and for Iw =1.0, from Tables 1609.6.2.1(2) and 1609.6.2.1(3).


FIGURE 1609.6.2.2
COMPONENT AND CLADDING PRESSURE

For SI: 1 foot = 304.8 mm, 1 degree = 0.0174 rad.

Notes:
  1. Pressures are applied normal to the surface for Exposure B, at h = 30 feet, for Iw = 1.0. Adjust to other exposures and heights with adjustment factor λ.
  2. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.
  3. For hip roofs with θ ≤ 25°, Zone 3 shall be treated as Zone 2.
  4. For effective areas between those given, the value is permitted to be interpolated, otherwise use the value associated with the lower effective area.
  5. Notation:

    a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4 percent of least horizontal dimension or 3 feet.
    h: Mean roof height, in feet (meters), except that eave height shall be used for roof angles < 10°.
    θ: Angle of plane of roof from horizontal, in degrees.
1609.6.2.2.1 Minimum Pressures
The positive design wind pressures, pnet, from Section 1609.6.2.2 shall not be less than + 20 psf (1.44 kN/m2), and the negative design wind pressures, pnet, from Section 1609.6.2.2 shall not be less than — 20 psf (-1.44 kN/m2).
1609.6.2.3 Load Case
Members that act as both part of the main wind force-resisting system and as components and cladding shall be designed for each separate load case.

Related Code Sections

1609.6.2 Structural Design, Simplified Design Procedure-I (For Low-Rise Buildings)
corner of the building in turn as the reference corner. For the design of the longitudinal MWFRS, use θ = 0°, and locate the Zone E/F, G/H boundary ...
1609.6.2.3 Structural Design, Load Case
Members that act as both part of the main wind force-resisting system and as components and cladding shall be designed for each separate load case ...