Compression only

A compression only structure is the ideal stereotomic realization, an abstraction that is mostly useful as an utopian archetype when the designer strives for most compression efficiency. A common image used in literature is that of voussoirs made of polished ice, removing any friction which would compensate for inaccuracies in voussoir materialisation.

A compression only structure is mainly characterized by the solutions employed, rather than the phenomena taking plane within the materials. In this type of structures, there is a strive to depend mainly in the compression resistance of materials owing much of the responsibility of structural efficiency to the correct distribution of forces due to a funicular^[1] shape.

Theoretically, it is possible to build a very thin funicular shell^[2] of a material which is very resistant to compression (such as ice), and it would remain structurally sound under gravity alone. Because of other forces (such as wind, or earthquakes) which are exerted by vectors other than -Z, this theoretical shell model is not plausible in a real case scenario and solutions ranging from larger overall shell thickness, contact face friction or voussoir interlock and tension resistant materials have always been applied throughout history.

[1] “The word funicular originates from the Latin word fu niculus meaning “cord, rope”. (…) Such a funicular form achieves a unique staticequilibriumforgivensupportpoints, ropelengthandloadingcase. Ahanginginelasticropewithoutanyadditionalweightsattached is a specific funicular shape known as catenary. A funicular form can be inverted, meaning its defined stress state changes for the same loading case from pure tension to pure compression.”(Matthias Rippmann, 2016)

[2] A shell structure is described by Williams (2014) as “a structure defined by a curved surface. It is thin in the direction perpendicular to the surface, but there is no absolute rule as to how thin it has to be.”