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Wind on sawtooth roofs with a slope between 10 and 30 degrees for C&C

Figure 4.1.7.6.-H (NBC2020)
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Climatic Data

Source
Region
Location
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Velocity Pressure
Return Period:
Reference Velocity Pressure
q:
kPa

Factors

Importance factor
Category:
Limit state:
Exposure Factor
Terrain:
Height, h:
m (Reference height in meters above grade)
Topographic Factor
Ct:
Internal pressure
Category, Cpi:
info
Building Openings: [CL: 4.1.7.1]
Category 1: Uniformly distributed small openings amounting to less than 0.1% of the total surface area of the building.

Category 2: Non-uniformly distributed openings of which none is significant or significant openings that are wind-resistant and closed during storms.

Category 3: Large openings likely to remain open during storms.

For cladding on parapets use Category 3.
Midheight of dominant opening (for Cei)
Midheight, hi:
m (leave empty if no dominant opening.)

Building

Roof pitch:
/12
Tributary Area, A:
m2
End-zone width, z
(If H or the least horizontal dimension are left blank, z will not be calculated.)
Building Height, H:
m (Height of building at eave)
Least horizontal dim:
m
Region
Region 'c'
Region 'r'
Region 's'
wind sawtooth 10-30

Factors

User input values:
q: 1kPa
Importance Factor, ULS: Iw = 1.0
Ce = (h/10)0.2 (but not less than 0.9) = 0.9
Roof slope: 26.57 degrees

External Wind Pressure

Using figure for sawtooth roofs with slopes between 10 and 30 degrees.
Zone CpCg pe (kPa)
c (Span A)-7.7-6.93
c (Spans B,C,D)-4.8-4.32
r--4.2-3.78
s--5.9-5.31
c+1.611.45
r+1.311.18
s+2.111.9

Internal Wind Pressure

Cgi = 2
Cpi = -0.45 to 0.3
Reference height (max H/2 or 6m)= 6 m
Cei = (hi/10)0.2 (but not less than 0.9) = 0.9

pi = Iw*q*Ce*Ct*Cgi*Cpi
pi = -0.81kPa to 0.54kPa

Combined Wind Pressure

Zone Cpi=-0.45
p (kPa) 		Cpi=0.3
p (kPa)
c- (Span A)-6.12-7.47
c- (Spans B,C,D)-3.51-4.86
c+0.912.26
r--2.97-4.32
r+0.641.99
s--4.5-5.85
s+1.362.71

End Zone Width

The end-zone width is the lesser of:
• 10% of the least horizontal dimension = 0.1m
• 40% of the height of the building (H) = 0.4m
but not less than:
• 4% of the least horizontal dimension = 0.04m
• 1m
z = 1m

This information must be read or used in conjunction with Part 4 of the NBC 2020. In the event of discrepancies, Part 4 of the NBC 2020 shall govern.

© 2009–2025 Modulo Software Inc.
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