Just as
the amount of load a truss bridge can carry relative to its own dead
weight, its L/W |
ratio,
is an important measure of its structural efficiency, so to is the ratio
of a spaceframe's |
module
size to its span. In general as the size of the module increases,
the number of |
struts
and hubs required to span a given area decreases. |
|
For
example, as shown by the following demonstration, doubling the module size
can |
reduce
the number of struts and hubs by a factor of four and the total length of
the struts |
by
one-half for a given span. |
|
|
|
a) module size = 5 units |
b) module size = 10 units |
. |
struts = 32 hubs = 8 |
struts = 8 hubs = 2 |
total strut length = 160 units |
total strut length = 80 units |
. |
Fig. 257 - Comparison of the number of
hubs and struts required to |
span 100 square units of area with different module sizes |
|
. |
The
economic cost of a spaceframe is due primarily to the number of hubs and
struts used |
in the
structure. As a result, doubling the module size can reduce the cost
by as much as |
one-half. As a rule of thumb, a spaceframe's module size should be 8
- 16 % of its span for |
greatest
structural and economic efficiency. |
|
Eliminating some of the struts and hubs used in the inner grid of the
Square-2 spaceframe |
results
in two variations called Square-1, and Square-3, which are more open
structures. |
|
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to Knowhere |
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Page 144
- Building stability - Square-2 spaceframe |
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