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As
the unstable unit cell shows, the lattice lacks stability in the |
 |
|
diagonal direction. It is vulnerable to twisting, or torsion, forces
if |
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its perimeter is not supported at all four corners. It is best
used for |
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short spans where only a few modules are required, or where the |
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loading is uniform across the structure and perpendicular to its
|
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plane. The figure to the right shows how this lattice can be
twisted |
|
into a curved hyperbolic parabola, or hypar, shape by making use |
Fig. 254 - Bus stop |
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of
its lack of torsional stability. |
with hypar cover |
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|
. |
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In a
variation of the Square-2 design, called Square 2a, the square
checkerboard pattern |
|
of the
grids is rotated forty-five degrees so that the perimeter slices the
outermost squares |
|
diagonally in half. This variation is useful for matching the angled
edge of a building. |
|
. |
|
 |
 |
 |
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click image to enlarge |
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a) outer grid (looking
down) |
b) strut diagram |
c) Kiosk with Square-2a roof |
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. |
|
Fig. 255 - Square-2a spaceframe
[demonstration model made with
small triangles (ST) ] |
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|
. |
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As with
the triangular spaceframes, the depth of square spaceframes can be
increased to |
|
increase
their spanning or load bearing capacity, When the depth/module ratio
is equal to |
|
0.707
all of the struts comprising the structure are the same length. |
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side
view |
|
 |
 |
 |
|
depth/module = .707 |
depth/module = .707 |
depth/module = 1.26 |
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top view |
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 |
 |
 |
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a) w/ small triangles (ST) |
b) w/ large triangles (LT) |
c) w/ isosceles triangles (IT) |
|
click image to enlarge |
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Fig. 256 - Square-2 unit cells with varying depth/module ratios
(demonstration models) |
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|
. |
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Back
to Knowhere |
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Page 143
- Building stability - Square-2 spaceframe |
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