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SWH Solar Racking Installation Guide | Version 12.10.v2
192a
STANDARDS 7-10
[1.2.] Procedure to Calculate Total Design Wind Load per ASCE 7-10
Step 3. Determine Wind Load Parameters
Step 3a:
Determine the proper Exposure
Category (B, C, or D)
for the project by
using the following definitions for Surface
Roughness Categories.
ASCE 7-10 defines wind surface
roughness categories as follows:
Surface Roughness B: Urban and suburban
areas, wooded areas, or other terrain with
numerous closely spaced obstructions
having the size of single-family dwellings
or larger.
Surface Roughness C: Open terrain with
scattered obstructions having heights
grasslands.
Surface Roughness D: Flat, unobstructed
areas and water surfaces. This category
includes smooth mud flats, salt flats, and
unbroken ice.
Step 3b:
Determine the Topographic
Factor, Kzt.
For the purposes of this code compliance
document, the Topographic Factor, K
zt
, is
taken as equal to one (1) as per Section
26.8-2 or as determined by Figure 26.8-1
in ASCE 7-10. Also shown in pages 13-14`.
Step 4. Determine Effective Wind Area
Determine the smallest area
of continuous modules you will be
installing. This is the smallest area
tributary (contributing load) to a support
or to a simple-span of rail. That area is
the Effective Wind Area, the total area of
the fewest number of modules on a run
of rails. If the smallest area of continuous
modules exceeds 100 sq ft, use 100 sq ft,
if less round down to values available in
Table 3, page 17.
Step 5. Determine the appropriate roof
zone for the installation.
The Design Wind Load will vary
based on where the installation is located
on a roof. Arrays may be located in more
than one roof zone.
Using Table 2, page 15, determine the
Roof Zone Dimension Length, a (ft)
,
according to the width and height of the
building on which you are installing the pv
system.
category includes flat open country and
generally less than 30 ft (9.1 m). This
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