RECIPROCAL FRAME STRUCTURES
Reciprocal frame structures are defined as a total of self-supported elements in a closed structure; a pretty comprehensive but difficult to assimilate definition without a good drawing as an example.
In the next picture is shown the simplest arrangement of a mutual structure: three bars that overlap to lean on each other and achieve a simple and elegant structural balance.
Reciprocal structures were proposed as an ingenious solution to the problem of covering a distance, or rather a surface, using elements of limited size. As shown in the schemes extracted from Reciprocal Frame Architecture Book, grids are formed by elements with lower dimension than the space to cover, being its geometrical arrangement which enables a stable structure.
It is a structural idea as simple as ancient. There were found building techniques based on this structural design in documents attesting that in Japan at the XII century and there are many different examples of building throughout history that have used structural arrangements based on this principle.
Maybe it was Sebastiano Serlio and Leonardo Da Vinci who established the first geometric and structural studies of reciprocity around 1500. A clear example of using a reciprocal structure can be found in the Codex Madrid of Da Vinci where is described how to build bridge wood beams.
We can see more recent examples such as those in the Catalan architecture of the early XX century by Josep Maria Jujol close associate of Antoni Gaudí, with reciprocal structures used in Bofarull Can Negre House around 1915.
More recently, Cecil Balmond and his team, the advance geometry unit of Arup designed the Weave Bridge for the University of Pennsylvania. Inspired, theoretically, in the structural principle of reciprocity.
Tensegrity structural principle is based on the use of isolated components are tensioned within a continuous network, such that the compressed elements (usually bars) do not touch each other and are connected only through pulling components (usually cables) that delimit spatially the system. The balance between both types of efforts lends rigidity and shape to the structure. This kind of construction combines extensive design possibilities with high strength and lightness and economy of materials.
Tensegrity structures were explored by the artist Kenneth Snelson, producing sculptures as Needle Tower, 18 meters high and built in 1968. The term “tensegrity” was adopted by Buckminster Fuller.
Fuller developed in the early 40’s geodesic domes, which among other structures, is the most emblematic and transcendent that came to conceive, which can still be seen at military installations, civil buildings and exhibitions. The idea of these domes was covering long distances at a lower cost. His most famous work was the sphere for the USA pavillion in the Universal Exhibition in Montreal in 1967, which was 76 m in diameter and 41’5 m high.
Its construction is based on the basic principles of tensegrity structures, which allow mounting simple structures assuring his tensional integrity (tetrahedral, octahedral and closed sets of spheres). Being made in this way is extremely lightweight and stable.
Construction of a geodesic and self-sufficient housing in Yecla, Murcia (Spain)
The frame of the dome has been executed in a short time, just four days, having previously assembled the triangles in workshop. The speed and the fact that is mounted in one operation structure and facade make these types of buildings a very economical construction.
After the wooden structure come the enclosure envelope, consisting of OSB wooden boards inwards and outwards (already cut in workshop), using recycled cellulose insulation and external coat of lime mortar.
Other fact is that the environmental impact of the work is minimal as is made of natural materials and much of the operation is made in the workshop, which greatly reduces dirt and debris.