Space Frames

A space frame refers to a spatial structure whose members are connected rigidly to each other so that they transfer moment and shear in addition to axial forces. In comparison, space trusses are pin-jointed and as a result, their members are in tension or compression and do not transfer moment or shear.

In most cases, the additional reduction in member forces and deflection of space frames is less than 10% as compared to space trusses. Therefore, the additional material required to provide rigid connections does not justify the saving in the size of structural members. As a result, the term “space frame” is also the term used for pin-jointed three-dimensional structures, such as space trusses. Space frames are also called ‘braced frameworks’, ‘latticed structures’ or ‘reticulated structures’.

Space frames are either constructed from prefabricated modular units (modular system) or individual members assembled together using different types of connectors or nodes (nodular system). These systems are typically proprietary.

It is also possible to construct space frames by field-welding members to each other; this is generally a more costly alternative. When field welding, the joints are considered to be rigidly connected, capable of transferring moment and shear in addition to axial forces.

Nature has many examples of repetitive spatial packing configurations used in space frames: The hexagonal prisms of honeycomb; plant cell organisms, the repetitive organization of crystals and snowflakes, etc. The triangle is the simplest stable geometry, which means that it is not possible to change its shape in-plane because there are three interconnected members. This is not the case for polygons such as squares, rectangles, hexagons, or octagons. The bracing members of space frames create the triangulation that stabilizes the structure.

Space frames generally consist of double and multi-layer grids in flat or free forms. Flat space frames have been typically used as roof systems, but they can also be used to support floors. Atriums, entryways, canopies, arenas, exhibit pavilions, hangars, convention centers, mosques, terminals, grandstands, sport facilities, reservoir covers, churches, swimming pool covers, shopping malls, stadium pavilions, sloped glazing, large-span warehouses, towers, space stations, and floating platforms may also be constructed from space frames.