As
the unstable unit cell shows, the lattice lacks stability in the 

diagonal direction. It is vulnerable to twisting, or torsion, forces
if 
its perimeter is not supported at all four corners. It is best
used for 
short spans where only a few modules are required, or where the 
loading is uniform across the structure and perpendicular to its

plane. The figure to the right shows how this lattice can be
twisted 
into a curved hyperbolic parabola, or hypar, shape by making use 
Fig. 254  Bus stop 
of
its lack of torsional stability. 
with hypar cover 

. 
In a
variation of the Square2 design, called Square 2a, the square
checkerboard pattern 
of the
grids is rotated fortyfive degrees so that the perimeter slices the
outermost squares 
diagonally in half. This variation is useful for matching the angled
edge of a building. 
. 



click image to enlarge 
a) outer grid (looking
down) 
b) strut diagram 
c) Kiosk with Square2a roof 
. 
Fig. 255  Square2a spaceframe
[demonstration model made with
small triangles (ST) ] 

. 
As with
the triangular spaceframes, the depth of square spaceframes can be
increased to 
increase
their spanning or load bearing capacity, When the depth/module ratio
is equal to 
0.707
all of the struts comprising the structure are the same length. 
side
view 



depth/module = .707 
depth/module = .707 
depth/module = 1.26 
top view 



a) w/ small triangles (ST) 
b) w/ large triangles (LT) 
c) w/ isosceles triangles (IT) 
click image to enlarge 
Fig. 256  Square2 unit cells with varying depth/module ratios
(demonstration models) 

. 
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to Knowhere 

Page 143
 Building stability  Square2 spaceframe 

