Installation Guide

Page
8
Unirac Code-Compliant Installation Manual SunFrame
R
1411 Broadway Boulevard NE
Albuquerque NM 87102-1545 USA
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
B C D
Table 4. Adjustment Factor (λ) for Roof Height &
Exposure Category
Source: ASCE/SEI 7-05, Minimum Design Loads for Buildings and Other
Structures, Chapter 6, Figure 6-3, p. 44.
Exposure
Mean roof
height (ft)
Step 7: Determine adjustment factor for height and
exposure category, λ:
Using the Exposure Category (Step 6) and the roof height, h
(ft), look up the adjustment factor for height and exposure in
Table 4.
Step 8: Determine the Importance Factor, I:
Determine if the installation is in a hurricane prone region.
Look up the Importance Factor, I, Table 6, page 9, using the
occupancy category description and the hurricane prone
region status.
Step 9: Calculate the Design Wind Load,
p
net
(psf):
Multiply the Net Design Wind Pressure,
p
net30
(psf)(Step 4) by
the adjustment factor for height and exposure, λ (Step 7),the
Topographic Factor, K
zt
(Step 5), and the Importance Factor, I
(Step 8) using the following equation:
p
net
(psf) = λK
zt
I p
net30
p
net
(psf) = Design Wind Load (10 psf minimum)
λ = adjustment factor for height and exposure category (Step 7)
K
zt
= Topographic Factor at mean roof height, h (ft) (Step 5)
I = Importance Factor (Step 8)
p
net30
(psf) = net design wind pressure for Exposure B, at height
= 30, I = 1 (Step 4)
Use Table 5 below to calculate Design Wind Load.
The Design Wind Load will be used in Part II to select the
appropriate SunFrame Series rail, rail span and foot spacing.
Variable Description Symbol Value Unit Step Reference
Building Height h ft
Building, Least Horizontal Dimension ft
Roof Pitch degrees
Exposure Category 6
Basic Wind Speed V mph 1 Figure 1
Effective Roof Area sf
2
Roof Zone Setback Length a ft 3 Table 1
Roof Zone Location 3 Figure 2
Net Design Wind Pressure
p
net30
psf 4 Table 2, 3
Topographic Factor K
zt
x 5
Adjustment factor for height and exposure category λ x 7 Table 4
Importance Factor I x 8 Table 5
Total Design Wind Load
p
net
psf 9
Table 5. Worksheet for Components and Cladding Wind Load Calculation: IBC 2009, ASCE 7-05