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Diagrams
Notation
a
h
θ
10% of least horizontal dimension or 0.4 h, whichever is smaller, but not less than either 4% of least horizontal dimension or 3 ft
(0.9 m).
EXCEPTION: For buildings with θ = 0 to 7° and a least horizontal dimension greater than 300 ft (90 m), dimension a shall be
limited to a maximum of 0.8 h.
Mean roof height, in ft (m), except that eave height shall be used for roof angles < 10°.
Angle of plane of roof from horizontal, in degrees.
Notes
1. Pressures shown are applied to the horizontal and vertical projections, for Exposure B, at h = 30 ft (h = 9.1 m). 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 (See Fig. 28.3-1).
3. For Case B, use θ = 0°.
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° and 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. 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.
9. Unit conversions for tables:
Adjustment Factor for Building Height and Exposure, λ
Exposure
Mean roof height (ft)
15
20
25
30
35
40
45
50
55
60
B
C
D
1.00
1.00
1.00
1.00
1.05
1.09
1.12
1.16
1.19
1.22
1.21
1.29
1.35
1.40
1.45
1.49
1.53
1.56
1.59
1.62
1.47
1.55
1.61
1.66
1.70
1.74
1.78
1.81
1.84
1.87
Note: Unit conversions for tables: 1.0 ft = 0.3048 m; 1.0 lb=ft2 = 0.0479 kN=m2 ; 1 mph = 1.6 km=h
FIGURE 28.5-1 Main Wind Force Resisting System, Part 2 [h ≤ 60 ft (h ≤ 18.3 m)]: Design Wind Pressures for
Enclosed Buildings—Walls and Roofs
continues
316
STANDARD ASCE/SEI 7-16