Square-3 Spaceframe: ( two-way small square outer grid over
two-way larger square |
inner grid) |
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click image to enlarge |
a) outer grid |
b) inner grid |
c) strut diagram |
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Fig. 262 - Square-3 spaceframe
[demonstration model built with
small triangles (ST) ]* |
* can also be built with LT, and IT |
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The
openness of the large square grid pattern of the inner layer is apparent.
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The unit
cell is inherently unstable against torsional movement. Like
Square-2, the entire |
structure
lacks torsional stability since both the outer and inner square grids run
parallel |
to each another. Therefore its perimeter must be adequately
supported to resist twisting. |
The framework can be
stabilized with panels or skylights inserted in the square openings. |
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Fig. 263 - Square-3 unit cell |
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click image to enlarge |
M = 52 J = 20 |
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52 < 3 (20 ) - 6 |
(demonstration model) |
unstable, need +2 M |
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In terms
of structural efficiency, it is midway between the more dense Square-2
design |
and the less
dense Square-1 spaceframe. |
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Fig. 264 - Carport with |
Square-3 roof |
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(scale visualization model) |
click image to enlarge |
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to Knowhere |
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Page 146
- Building stability - Square-3 spaceframe |
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