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
onehalf 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 
onehalf. 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
Square2 spaceframe 
results
in two variations called Square1, and Square3, which are more open
structures. 

Back
to Knowhere 

Page 144
 Building stability  Square2 spaceframe 

