ME 309 Fall 2008
Section 2
Homework # 33
Due Friday 21 November 2008
Problem 331
A fiftystory office building in Chicago is 170
m
tall and is square with
30
m
long sides. Ignoring end effects, estimate the drag force exerted on the building
for wind velocities of 5, 15, and 45
m/s
at the following two directions:
a)
The wind is aligned with the face of the building and strikes the left side of the
building head on.
b)
The wind is aligned at 45° to the building.
The local temperature in Chicago is 250
K
, and the pressure is 1
atm
.
The viscosity may
be found from Sutherland’s law:
S
T
S
T
T
T
+
+
=
0
2
/
3
0
0
μ
μ
For air at normal temperatures, the coefficients in Sutherland’s law are given by:
s
m
kg
⋅
×
=

/
10
716
.
1
5
0
μ
,
K
T
273
0
=
,
K
S
111
=
c)
The same building is transported to Miami where the temperature is 305
K
but the
wind is still the same.
What effect does the increased temperature have on the
loading by the 45
m/s
wind?
Consider only the strongest wind aligned with the
building.
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 Spring '08
 MERKLE
 Drag force, frontal area

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