Tri-3
spaceframe: (three-way
triangular outer grid over three-way hexagonal inner grid) |
. |
The
Tri-3 spaceframe is created by periodically removing groups of six struts
from the |
inner
layer of the Tri-1 design. This forms a honeycomb-like inner layer
of edge-connected |
hexagons. Some diagonal struts are also removed. |
. |
 |
 |
|
click image to enlarge |
a) outer grid |
b) inner grid |
c) strut diagram |
. |
Fig. 237 - Tri-3 spaceframe
[demonstration model constructed from
small triangles (ST) ] |
|
. |
As with
the model of the Tri-1 unit cell shown previously, the depth of the Tri-3
model can |
be
varied by using right triangles (RT), large triangles (LT), or isosceles
triangles (IT). |
|
A
stability analysis of the unit cell of the Tri-3 spaceframe indicates that
it is inherently |
unstable (Fig. 238 a) |
|
|
|
a) M = 27 J = 12 |
b) M = 30 J = 12 |
c) M = 30 J = 12 |
27 < 3 ( 12 ) - 6 |
30 = 3 ( 12 ) - 6 |
30 = 3 ( 12 ) - 6 |
unstable, need +3 M |
stable |
stable |
click image to enlarge |
Fig. 238 - Stability analysis of the Tri-3 spaceframe unit cell
(demonstration models) |
|
. |
Theoretically, the cell can be stabilized by inserting three more bracing
struts as shown in |
either
b) or c) above to create a hybrid structure. Or rigid panels or
skylights can be |
inserted
into the hexagonal openings of the inner layer to stabilize the structure
by means |
of plate
action as shown in Fig. 239 following. Either way, adequate perimeter support |
must be
provided to help stabilize the structure. |
. |
 |
◄ Fig. 239 Tri-3 spaceframe |
 |
stabilized with skylights |
|
Fig. 240 Toll booth with |
Tri-3 spaceframe roof ► |
(scale visualization model) |
click images to enlarge |
|
. |
Back
to Knowhere |
 |
Page 138
- Building stability - Tri-3 spaceframe |
 |
|