Reciprocal Structures (Reciprocal Frame)
Introduction
A reciprocal frame is a three-dimensional assembly of mutually supporting elements.
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Characteristics
The principle of structural reciprocity, that is, the use of load-bearing elements to compose a spatial configuration in which they are mutually supported by each other, has been known since ancient times. Its characteristics are:
• - A certain coefficient of friction between them is necessary to achieve balance.
• - The minimum number of elements required is three.
• - The basis of its balance lies in the fact that one element is supported by the next element, and so on, until the last element is finally supported by the first, closing the circle of self-sustaining.
• - A reciprocal frame structure can be decomposed into basic elements that circumscribe a polygon "Polygon (geometry)") with at least three of its sides for which the figure can be regular or irregular. A reciprocal raster structure can be constructed from identical or non-identical building blocks, as long as a tessellation pattern exists.
In the world of construction, the application of the principle of reciprocity requires:
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- The presence of at least two elements that allow the generation of a certain forced interaction.
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- That each element of the composition must support and be supported by another.
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- That each support element must fulfill its support along its length and never at the vertices.
The joining of the elements at the contact points can generally be carried out without mechanical connections, but only by pressure and friction. To support the friction force, there are simple connection techniques such as tying the elements or making notches in the elements at the contact points. Directly dependent on the development of the connections is the deformation of the entire system under load. The increase in slip that occurs with simple joining, such as tying the elements, results in an increase in the deformability of the entire structure.
This type of structures has the ability to span spans (or rather cover surfaces) greater than the lengths of its elements, its geometric arrangement being what makes a stable structure possible. Normally its elements are beam type, although those formed by equal elements can also be accepted as reciprocal structures. As they do not need external support elements, they are used to build bridges, decks or similar structures.[2].