Department of Architecture and Civil Engineering

Flexibly formed concrete structures

At a glance

Funding: EPSRC CASE Award with Atkins Ltd
Researcher: John Orr
Supervisors: Antony Darby (lead), Tim Ibell and Mark Evernden
Industry partners: Mike Otlet (Atkins Ltd)
Dates: 2009-2012

Objectives

  • To develop design, optimisation and construction techniques for fabric formed concrete structures
  • To carry out full scale structural testing and verification of proposed methods.

Details

Cement, 2.8x109t of which was produced worldwide in 2007, results in a global concrete usage approaching 1.5m3 per person per year, making concrete our most widely used man made material. Whilst its constituent raw materials are widely available and easily extracted, cement has high embodied energy and its manufacture is estimated to account for 3% of global CO2 emissions.

This suggests that concrete should be cast in optimised structures that minimise material use and take advantage of the mouldability of concrete. Concrete’s fluidity is rarely exploited and today tends to be cast in rigid, material intensive formwork systems. The optimisation of concrete structures such that they use less material, are structurally efficient and easy to construct will bring real innovation.

Using fabric formwork, it is possible to cast architecturally interesting, structurally optimised shapes based on simple design rules that are analogous to the growth of bone. When a bone is overstressed, it grows; when it is understressed, it atrophies. Fabric formwork can be used in the construction of optimised concrete structures to place material only where it is required, and research has shown that this is both a predictable and practical approach that can achieve material reductions of up to 50% when compared to an equivalent orthogonally cast beam. The principal advantage of fabric formwork lies in its simplicity, allowing the casting of unique structures using readily available, inexpensive materials.

Previous work in this field has focused predominantly on the architectural applications of fabric formwork, and relatively few full-scale structural tests have been carried out. Therefore, the main objectives of this project are to develop, test and verify the design, optimisation and construction methods required for the fabrication of flexibly formed concrete beams. In doing so, current concerns surrounding the provision, location and anchorage of longitudinal and transverse reinforcement will be resolved, thereby facilitating the future design of fabric formed concrete structures.

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