Read here about tensegrity concepts as they relate to the tree.
A tree is considered here to be any plant with the general form of an elongated stem, or trunk, which supports the photosynthetic leaves or branches at some distance above the ground.
The original research agenda that culminated in the discovery of tensegrity was deeply inspired by trees. Richard Buckminster Fuller studied the trees in Lincoln Park, Chicago as he considered remaking shelter by isolating tension and compression. The original Dymaxion House had a tree-like pattern, with a central core (or trunk) supporting wires (branches) that formed the floors of the living quarters. Trees remained a constant trope in Fuller's lectures, he often spoke of the resilience of their structure and how their tension was enabled by water.
Tensegritree, Kent UK
The Tensegritree is a tree-like tensegrity sculpture, located on the Kent School of Architecture (KSA) campus between the Marlowe Building and the Templeman Library. The Tensegritree provides a canopy over a landscaped, outdoor teaching area on campus.
First conceived by Professor Don Gray in early 2013 and finished in 2015 the Tensegritree is a permanent memorial celebrating the 50th Anniversary of the University of Kent, and the 10th Anniversary of the founding of Kent School of Architecture. The idea for the structure dates back to the original planned extension of the library by architects Penoyre and Prasad, which included a designated space for a sculpture. Don Gray said, "As the excavations for the library continued, it was clear that a number of trees were being removed. This encouraged me to make a bid to produce something that marked the trees that had gone as well as celebrating both the University’s 50th and KSA’s 10th birthdays.]]
The sculpture was created by an international team of architects and engineers led by KSA Head, Professor Don Gray. Don Gray is a practising architect and academic, who worked with the visionary architect Cedric Price, and built major projects with Richard Rogers, Renzo Piano and Nicholas Grimshaw among others. In a distinguished teaching career, he has held senior appointments at the Bartlett and Architectural Association Schools in London and has written new learning programmes for De Montfort University and the University of the Arts, London.
The starting-point for the University’s Tensegritree structure was inviting world-leading tensegrity expert, Professor Andrea Micheletti to Kent. He worked alongside BA and MArch students of architecture at KSA to come up with a number of potential designs, before deciding on a central trunk with cantilevered tensegrity “branches”. The chosen design was subjected to a feasibility study conducted by Expedition Engineers (the team behind the London Olympic Velodrome) and tensegrity experts from the University of Cambridge. Contractor ES Global was then appointed to develop the design, with the help of KSA specialists including its digital workshop team, who produced 3D images to perfect the joints of the new structure. Assembly of the structure took less than one week on site and was unveiled by the Kent School Vice-Chancellor on the eve of the 50th Festival celebrations from 4-6 September 2015.
Standing at 7m high and 12m diameter, the structure comprises galvanized steel – for the compressive ‘strut’ elements – and stainless steel rods – for the tensile cable elements. The final stage is to create a seating area on the compass points below the structure, to provide the best viewing-points for the tensegrity elements.
The Role of Expedition Engineering
Expedition Engineering is an award-winning civil and structural engineering design practice based in central London. They wrote this report:
In 2014 Expedition were approached by Don Gray, head of the Kent School of Architecture, with a request to help create a placemaking sculpture to commemorate the 10th anniversary of the department and the 50th anniversary of the University of Kent in the summer of 2015. The brief was for a sculpture based on tensegrity principles which would create intrigue through the relationship between form and force, architecture and engineering. It was quickly apparent that without an unrealistically large budget this sculpture structure could never be the tallest/biggest/longest ever tensegrity. Rather the project was about creating something unique, a talking point at the entrance to the architecture faculty within a limited budget (as appropriate for a public body): a new tensegrity form.
Tensegrity structures, comprising a network of stressed cables and seemingly ‘floating’ compression members, are by their very nature difficult to build. They are amongst the least intuitive of structural engineering typologies to design and analyse, due to complex interdependent technical issues (effects of prestress, non-linearities, very low stiffness , form-finding, etc.). The fundamental mechanical behaviour is more complex than, say, concrete-framed buildings, lightweight footbridges, long span timber roofs, cable nets… Technical complexity also comes with the risk that key stakeholders, such as clients and building users, see it as a black-box design solution which they are not able to ‘own’ and do not feel a part of.
With the above challenges we could see from the outset that we needed to assemble the right experts to collaborate on the project. We invited:
- Prof Andrea Michaletti, University of Rome, with his expertise in physical modelling and form development of tensegrities, enabled us to run tensegrity model making workshops with the Kent architecture students; thereby having real engagement with the project and a sense of ownership, developing their ideas into the final sculpture form.
- Howard Woodliffe and Olly Watts, ESGlobal. As contractors with a track record of delivering unusual lightweight structures, it meant that all the way through the design process the team was developing proposals which were economic and practical.
- Dr Simon Guest, University of Cambridge, an academic specialist in mathematical stability modelling and mechanics. Simon provided validation of the Expedition design and insights to help resolve key technical challenges in a timely manner.
- Brian Wood, Kent School of Architecture technician and model making specialist, through whom prototyping enabled the students and client body to see the evolving sculpture and also the design team to test and refine key details.
- Don Gray, head of Kent School of Architecture, a well-informed client who engaged throughout the design and construction process; decisions were made based on a good understanding of the potential benefits and uncertainties of experimentation.
We have been involved with the International Association of Shell and Spatial Structures for a number of years, and the TensegriTree was presented and well received at the 2015 annual conference. Such is the complexity of realising tensegrity structures at-scale that one university research group planned to build one in a week, and ended up taking all summer. Another tensegrity sculpture had been immaculately designed by practicing engineers, but no contractors would tender for the job so it never got built!
References and Links
Kent Architecture School project: []
Kent Architecture School news release: []
Don Gray's faculty web page []