Square-3 Spaceframe:  ( two-way small square outer grid over two-way larger square

                                       inner grid)

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click image to enlarge

a) outer grid

b) inner grid

c) strut diagram

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Fig. 262 - Square-3 spaceframe  [demonstration model built with small triangles (ST) ]*

* can also be built with LT, and IT

 

The openness of the large square grid pattern of the inner layer is apparent. 

 

The unit cell is inherently unstable against torsional movement.  Like Square-2, the entire
structure lacks torsional stability since both the outer and inner square grids run parallel
to each another.  Therefore its perimeter must be adequately supported to resist twisting.
The framework can be stabilized with panels or skylights inserted in the square openings.
 

 

 

square-3_spaceframe.jpg

 

Fig. 263 - Square-3 unit cell

 

 

click image to enlarge

M = 52     J = 20

 
 

52 < 3 (20 ) - 6

(demonstration model)

unstable,  need +2 M

 

 

 

 

In terms of structural efficiency, it is midway between the more dense Square-2 design

and the less dense Square-1 spaceframe.

 

 

 

 

Fig. 264 - Carport with

Square-3 roof

 

(scale visualization model)

click image to enlarge

 

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Page 146 - Building stability - Square-3 spaceframe

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