Other long span structures employ networks of interconnected grids.  These include grids,

spaceframe lattices, and vaults.  These "space" structures have considerable width as well

as length.  They are designed to support external loads applied perpendicular to their

plane.  This is in contrast to relatively narrower, long span structures such as bridges, that

are designed to support loads applied parallel to their plane.





Fig. 223 - Loaded planes


◄  a)  parallel to plane

b) perpendicular to plane ►

(demonstration models)

click image to enlarge




Grids, or tessellations, are planar structures created from the intersection of regularly

spaced parallel members that form a repeating pattern of polygons.  Grids can be broadly

classified by the number of differently oriented parallel lines that intersect to form the grid

pattern.  Fig. 224 a), below shows a two-way pattern in which the members run parallel to

the boundary of the grid (i.e. lines oriented 0o and 90o).  Figure b) is an identical two-way

grid but the lines run diagonal to the boundary (i.e. 45o and 135o).  Figure c) is a three-way,

grid with lines parallel to 90o, 150o, and 210o.  Variations of these grids can be created by

the systematic elimination of some of the members to form more open grids. 



a)  two-way grid

b) two-way grid

c ) three-way grid

0o and 90o

45o and 135o

90o, 150o, and 210o


Fig. 224 - Two-way and three-way grid patterns    (visualization models)


Exercise:  Draw or model other types of two-, three-, or ?-way grids you can imagine.


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Page 132 - Building stability - Grids

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