You
should understand from these demonstrations that the geometry of the
stable, hinged |
triangle
structure allows several essential things to happen. The external
forces and |
internal
reactions are intimately linked. That is, increasing the external
forces directly |
increases the internal reactions. Also the internal compressive and
tensile stresses induced |
by the
external load and the internal compressive and tensile reactive forces
exerted by |
the
structure's material are in direct opposition to each other. As a
consequence these |
internal
induced and reactive forces are aligned axially, that is, parallel to each
other along |
the
longitudinal axis of the members. It is these properties that cause
the hinged triangle |
structure to be stable since they enable the external and internal forces
to be balanced. |
. |
Now that
you have a basic understanding of what makes structures stable and how
external |
loads
cause structural members to experience compressive and tensile stresses;
let's see |
how
these factors affect the design and performance of real structures like
columns, beams, |
bridges,
buildings, spaceframes, and towers. |
. |
 |
. |
Columns
and beams of some form are the fundamental building blocks of most
man-made |
structures. They are complimentary structural elements that function
together to enclose |
space or
support a framework. Columns (colored green above) are upright members
whose |
function
is to support an elevated framework and transfer its loads to the ground.
They are |
subjected to compressive stresses mainly since they are being squeezed
between the load |
bearing
down on the top of the column and the ground pushing back on the base of
the |
column.
Beams (colored yellow above) are horizontal members that span between
columns |
or
walls. Their function is to collect the load of the elevated
framework of which they are a |
part and
transfer it to the tops of the columns or walls. They are subjected
to bending |
induced
stresses of tension and compression mainly since they are supported on
their ends |
by
columns or walls and loaded in the middle by the weight of the elevated
framework. |
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Back to
Knowhere |
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Page 84 -
Building stability - Columns and beams |
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