Spaceframe
lattices |
|
 |
Two single layer grids can also be stacked on top of each other so |
that the grid pattern of one layer is staggered relative to the grid
of |
the other layer (Fig. 227). The joints of one grid are aligned
with |
the center
points of the polygons of the other grid like dual |
tessellations. As a result the web elements, or struts, form
oblique |
angles with the grids they span between.
Fig. 228 following |
shows an example of two staggered,
single layer, three-way grids |
click to enlarge |
that are connected together with struts to form a completely |
Fig. 227 - Staggered |
triangulated lattice structure, or spaceframe. In this
particular |
three-way grids |
spaceframe, all of the struts making up the grid and web of the |
|
|
lattice
are of equal length. Each facet, or face, of the lattice is an
equilateral triangle. |
As
a structural framework it is
commonly referred to as a Tri-1 spaceframe, or octet truss. |
. |
 |
|
 |
Fig. 228 -Tri-1 spaceframe |
(octet truss) |
overhead view ► |
(static demonstration model) |
click image to enlarge |
|
. |
One of
the first practical uses of the octet truss lattice was a man-carrying
kite invented |
|
by Dr.
Alexander Graham Bell in 1907. This lattice was also |
 |
popularized later by R. Buckminster Fuller as the isotropic |
vector matrix, or IVM. Readers of the prior lesson on |
geometry will recognize it as a space filling of tetrahedra |
and octahedra in the ratio of two to one respectively. |
|
◄
Fig. 229 - Cygnet tetrahedral kite (Bell,
1907) |
click image to enlarge |
|
. |
It is
also identical to the FCC crystal lattice structure presented in the
previous lesson on |
crystallography. The Tri-1 spaceframe can be cut out of the
FCC crystal lattice by slicing |
it
parallel to the 111 plane. Two other basic spaceframe lattices
can be sliced out of the |
|
octet truss also. One is a two-way square lattice, called |
 |
the Square-2 spaceframe, which is a slice taken parallel |
to the
100 plane.
The other is a two-way rectangular |
lattice, Rec-2,
which is sliced parallel to the 110 plane. |
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Fig. 230 - Slicing the octet truss (blue) to
reveal the Tri-1 |
(purple), Square-2 (red), and Rec-2 (green) spaceframes |
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to Knowhere |
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Page 134
- Building stability - Spaceframe lattices |
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