Buildings |
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Thus far we have discussed primarily how structures like beams,... |
columns, and bridges support downward acting loads applied in |
the same plane as the structure. That is, basically parallel
to the |
two dimensions of height and span. Buildings, however, can |
experience significant sideways, or lateral, loads also due to |
two-dimensional loading |
|
winds blowing against the exposed walls, snowdrifts, earthquakes,
etc. This is in addition to |
vertical acting external and internal loads such as snow, and loads
borne by the floors above |
ground.
In the following section you will see how structural engineers stabilize
buildings, |
spaceframes, and towers to withstand forces in three-dimensions. |
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Three
dimensional stability |
. |
Building
designs vary widely to serve many different purposes. In simplest
terms, a building |
can be
considered to be a three-dimensional box-like framework designed to
envelop an |
interior
space. Attached to this framework is a floor upon which rests the
people, animals, |
and
equipment being housed; a roof that shelters the interior from rain, snow,
and wind; |
and
walls that support the roof and supply shelter. The skeletal
framework is created by |
joining
beams and columns end to end at right angles to each other like the edges
of a cube. |
When the
sides of this box are viewed face-on the inherent instability of each of
the square- |
shaped
faces is self-evident. Recall the previous discussion of stable
polygons. |
. |
|
 |
Fig. 194 - Instability of the |
|
square faces of a cube |
|
◄ 4 < 2 ( 4 ) - 3 |
|
therefore unstable |
|
(visualization model) |
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. |
There
are four basic ways to stabilize the structural members framing the faces
of a cube. |
. |
 |
 |
 |
 |
a) single cross brace |
b) double cross brace |
c) diaphragm |
d) rigid joints |
. |
Fig. 195 - Four basic ways of stabilizing the faces of a cube
(visualization models) |
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to Knowhere |
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Page 117
- Building stability - Buildings |
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