CVEEN 3210, Fall 2016
Solutions
HW # 4
1
Problem I.
Compute the design wind pressures on the following steel building for the wind direction
shown in the figure for all walls and roof, according to ASCE 7
‐
10. Assume the following:
a. The penthouse is a rigid structure.
b. The building is located on an open terrain in one SLC, UT suburb.
c. It is an enclosed building.
d. The building is in a flat terrain.
SOLUTION:
The penthouse is located in SLC, UT.
The building is considered Category II (Table 1.5-1), and
from Figure 26.5-1A, the wind speed is 115 mph.
The building is in a flat terrain and, therefore, the topographic factor,
ܭ
௭௧
= 1.
Load combinations will be computed. Thus, the wind direction factor for a building is
ܭ
ௗ
= 0.85,
according to ASCE Table 26.6-1.
Then, the static wind pressure is modified by several factors to obtain
ݍ
௭
, at a height
ݖ
:
ݍ
௭
ൌ 0.00256ܭ
௭
ܭ
௭௧
ܭ
ௗ
ܸ
ଶ
ൌ 0.00256ܭ
௭
ሺ1.0ሻሺ0.85ሻሺ115ሻ
ଶ
ൌ 28.78ܭ
௭
ሺݏ݂ሻ
To compute
ݍ
௭
as a function of the height, we take into account that the building is in
open
terrain
. Thus, the Exposure Category is C, and based on ASCE Table 27.3-1:
Height (ft)
ࢠ
(Cat. B)
ࢠ
(psf)
0-15
0.85
24.46
15-20
0.90
25.90
20-25
0.94
27.05
25-30
0.98
28.20
30-40
1.04
29.93

CVEEN 3210, Fall 2016
Solutions
HW # 4
2
For the wind pressure at the mean roof height (
ݍ
), we need to consider that the height is
݄
= 40
ft. Thus, by linearly interpolating we find that
ܭ
௭
= 1.04, and that
ݍ
ൌ ݍ
,ସ௧
= 29.93 psf.
Once the
ݍ
௭
and
ݍ
values have been computed, we can get the design wind pressures based
on the equation:
ൌ ݍܩܥ
െ ݍ
ሺܩܥ
ሻ
Because the building can be considered enclosed,
ܩܥ
ൌ
േ
0.18 (Table 26.11-1). Also, the
structure is assumed to be a rigid building, and the gust factor can be taken as
ܩ
= 0.85. Then,
the equation can be expressed as:
ൌ ݍሺ0.85ሻܥ
െ 29.93ሺേ0.18ሻ ൌ 0.85ݍܥ
∓ 5.39
psf
The pressures at different surfaces are:
Windward Wall
This is the only surface in which
ݍ ൌ ݍ
௭
. Also, based on ASCE Table 27.4-1,
ܥ
= 0.8.
௪,ିଵହ
ൌ 0.85ݍܥ
∓ 8.5 ൌ 0.85ሺ24.46 ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݏ݂ ൌ . ∓ . ૢ ݏ݂
௪,ଵହିଶ
ൌ 0.85ሺ25.90 ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݏ݂ ൌ ૠ. ∓ . ૢ ݏ݂
௪,ଶିଶହ
ൌ 0.85ሺ27.05 ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݏ݂ ൌ ૡ. ૢ ∓ . ૢ ݏ݂
௪,ଶହିଷ
ൌ 0.85ሺ28.20 ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݏ݂ ൌ ૢ. ૡ ∓ . ૢ ݏ݂

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