Folded plate structures |
. |
As you
saw previously, plate-like structures have significant strength in
resisting shear |
stresses. Therefore they are used extensively to strengthen building
frameworks against |
wind and
seismic shear loads. Plates are also used on their own to build
stable structures |
like the
plate girders shown before. Such plate structures may be comprised
of relatively |
thin,
lightweight material such as plywood, fiberglass, aluminum plate, thin
plastic sheet, |
reinforced concrete, and even glass. This is due to the fact that
plate action dissipates the |
load
over the entire surface of the plate, which is then concentrated at the shear
line joints |
where
the plates
meet. |
. |
However,
an unsupported thin plate has relatively weak compressive strength.
It tends to |
buckle
easily when subjected to a load parallel to its plane (i.e. edge on), or
bend easily |
when
loaded perpendicular to its surface. This weakness can be
partially overcome by |
simply
folding the plate in an accordion-like, or corrugated, fashion.
This causes the plate |
. |
 |
Fig. 293 - Plate corrugation |
 |
◄ buckling of |
a thin plate |
corrugating the plate |
for rigidity ► |
(training aid model) |
click mage to enlarge |
|
. |
to be
triangulated thereby increasing its effective thickness, or height.
The corrugated |
plate
can now resist buckling and bending by plate-like action which resists the
tendency |
of the
individual folds of the plate to shear past each other. Each fold
also acts like an |
A-frame truss whose
strength is dependent on the height of the fold's peak versus the width |
of the channel between
the folds, that is its H/S ratio. The corrugated plate can be
further |
stabilized by bracing the ends of the V-shaped channels so that the plate
does not flatten |
out
under a perpendicular load. |
. |
 |
◄ Fig. 294 - Bracing a folded |
 |
plate to resist deflection |
|
Fig. 295 - Temple with |
corrugated roof ► |
(scale visualization model) |
click image to enlarge |
|
. |
Arching the folded plate strengthens it even more so that it |
 |
can enclose large spaces without the need for additional |
support. For example, corrugated steel plates are often |
used for aircraft hangers and warehouses. |
|
Fig. 296 - Aircraft hanger with corrugated
roof ► |
(scale visualization model built with LT (orange) and IT (blue) |
|
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to Knowhere |
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Page 154
- Building stability - Folded plate structures |
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