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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