Square-1 spaceframe: (two-way small square outer grid rotated 45o
relative to two-way |
large square inner grid) |
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click image to
enlarge |
a) outer grid |
b) inner grid |
c) side view |
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Fig. 258 - Square-1 spaceframe
(demonstration model constructed from ST
and RT) |
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The
struts of the inner grid are 1.414 times longer than the struts of the
outer grid. |
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The unit
cell is inherently unstable. The lattice can be stabilized by adding
extra bracing |
struts
to its perimeter cells as shown in Fig. 258 b) above (orange). Panels or skylights |
inserted
into the square openings will further stabilize the structure. Also,
sufficient support |
must be given to the perimeter for torsional stiffness. |
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M = 16 |
J = 8 |
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16 < 3 ( 8 ) - 6 |
unstable, need +2 M |
RT (blue), ST (yellow) |
(demonstration model) |
click image to enlarge |
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Fig. 259 - Strut diagram |
Fig. 260 - Square-1 unit cell |
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The
Square-1 design is more efficient than Square-2 because it has one-half
the number of |
diagonal
struts and fewer, longer struts in its inner grid. This is an
advantage for long |
spans
since the inner struts experience tensile stresses primarily. Thus their
slenderness |
ratio is
not a concern. Also the diagonal arrangement of the inner grid
relative to the outer |
grid
gives it increased torsional stability compared to the Square-2 design.
As a result the |
Square-1
design uses about 80 % of the material used in Square-2 for a given span. |
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Fig. 261 - Square-1 glazing |
framework for solarium |
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(scale visualization model) |
click image to enlarge |
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to Knowhere |
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Page 145
- Building stability - Square-1 spaceframe |
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