reciprocal frame
{{Short description|Arrangement of construction beams}}
File:Three stick reciprocal frame.JPG
A reciprocal frame is a class of self-supporting structure made of three or more beams and which requires no center support to create roofs, bridges or similar structures.
Construction
Reciprocal roofs tend to be constructed in one of two ways. If built using dimensioned timber, each rafter is usually jointed into the previous one. More commonly, these roofs are constructed with roundwood poles where each rafter is laid upon the previous one. In both of these approaches, the roof is assembled by installing a temporary central support that holds the first rafter at the correct height. The first rafter is fitted between the wall and the temporary central support and then further rafters are added, each resting on the last. The final rafter fits on top of the previous rafter and under the very first one. The rafters are then tied before the temporary support is removed. The structure is most effective at lower pitches where there is minimal spreading force exerted at the ringbeam, most being transferred directly downward. Unless some extra elements are added to create redundancy, the structure is only as strong as the weakest element, as the failure of a single element may lead to the failure of the whole structure.
History
The reciprocal frame, also known as a Mandala roof,{{cite book|url=https://books.google.com/books?id=3zp2hEozZ-oC&q=reciprocal+frame+mandala&pg=PA7|title=Reciprocal Frame Architecture | isbn=978-0-7506-8263-3 | year=2008 | publisher=Architectural Press}} has been used since the twelfth century in Chinese and Japanese architecture although little or no trace of these ancient methods remain. More recently they were used by architects Kazuhiro Ishii (the Spinning House) and Yasufumi Kijima, and engineer Yoishi Kan
Villard de Honnecourt produced sketches showing similar designs in the 13th century{{cite book|title=Reciprocal Frame Architecture|page=14|isbn=978-0-7506-8263-3|last1=Larsen|first1=Olga Popovic|year=2008}} and similar structures were also used in the chapter house of Lincoln Cathedral.{{cite book|title=Reciprocal Frame Architecture|page=9|isbn=978-0-7506-8263-3|last1=Larsen|first1=Olga Popovic|year=2008}} Josep Maria Jujol used this structure in both the Casa Bofarull and Casa Negre.{{cite book|title=Reciprocal Frame Architecture|page=8|isbn=978-0-7506-8263-3|last1=Larsen|first1=Olga Popovic|year=2008}}
Gallery
File:Simple reciprocal frame.JPG
File:Double reciprocal frame.JPG
File:Triple layer reciprocal frame roof.JPG
File:Grid reciprocal frame.JPG
File:Reciprocal frame roof.JPG
File:Longer reciprocal frame bridge.JPG
File:Leonardo da Vinci bridge Karby.jpg
File:Roundhouse moon.jpg|A design using primary & multiple secondary infill rafters (Tony Wrench)
File:Wholewoods reciprocal roof 0010.jpg|A design using primary & half length secondary rafters (Wholewoods)
File:Wholewoods reciprocal roof 0016.jpg|A design using primary and full length secondary rafters (Wholewoods)
File:Wholewoods reciprocal roof 0012.jpg|A redundancy technique using double rafter design (Wholewoods)
File:Wholewoods Reciprocal roof 0011.jpg|A primary rafter and purlin design (Wholewoods)
File:Wholewoods reiciprocal roof 0014.jpg|High frequency primary rafter design (Wholewoods)
File:Wholewoods reiciprocal roof 0013.jpg|Secondary reciprocal design (Wholewoods)
File:Roundhouse roof construction interior view.jpg
File:Reciprocal frame roof before turf.jpg
References
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External links
- [https://web.archive.org/web/20111109190659/http://www.designforward.net/newsletter04_2003.shtm Design forward]
- [http://greenbuildingelements.com/2008/10/01/the-reciprocal-roof-beauty-strength-and-simplicity-in-a-roof-frame/ Green Building elements]
- [https://books.google.com/books?id=3zp2hEozZ-oC Reciprocal Frame Architecture] by Olga Popovic Larsen
- [http://cat.inist.fr/?aModele=afficheN&cpsidt=2299273 The variety of reciprocal frame (RF) morphologies developed for a medium span assembly building : A case study]