Concrete structures using fabric formwork

Using fabric formwork, it is possible to cast architecturally interesting, optimised structures that use up to 40% less concrete than an equivalent strength prismatic section, thereby offering the potential for significant embodied energy savings in new concrete structures. This paper reports on the philosophy of and background to fabric formwork before techniques for the design, optimisation and shape prediction of fabric formed concrete beams are presented. The practicality of construction with non-orthogonal elements is discussed before the results of new structural test data, undertaken at the University of Bath on 4m span ’T’ beam elements formed in reusable fabric moulds, are presented. Potential areas of future development for fabric formwork, including the use of woven advanced composite fabrics as permanent participating formwork and the feasibility of uniform strength prestressed beams, are then discussed The practicality of construction with non-orthogonal elements is discussed before the results of new structural test data, undertaken at the University of Bath on 4m span ‘T’ beam elements formed in reusable fabric moulds, are presented. Potential areas of future development for fabric formwork, including the use of woven advanced composite fabrics as permanent participating formwork and the feasibility of uniform strength prestressed beams, are then discussed

Experimental Investigation of Reinforced Concrete T-Beams Strengthened in Shear with Externally Bonded CFRP Sheets

An experimental investigation was undertaken into the effectiveness of unanchored and anchored externally bonded (EB) U-wrapped carbon fibre reinforced polymer (CFRP) shear strengthening for reinforced concrete T-beams at a range of realistic sizes. The T-beam sizes, geometry and reinforcement were chosen to reflect existing slab-on-beam structures with low levels of transverse steel shear reinforcement. Geometrically similar reinforced concrete T-beams were tested across three sizes ranging from 360 to 720 mm in depth and with different amounts of EB CFRP shear reinforcement. The beams were subjected to three-point bending with a span to depth ratio of 3.5. All the beams failed in diagonal shear. The experimental results indicate significant variability in the capacity of unstrengthened control beams, and a number of these control beams showed greater shear capacity than their EB CFRP strengthened counterparts. Greater thicknesses of CFRP reinforcement did not lead to increased shear capacity compared with lesser thicknesses of unanchored or anchored EB CFRP, but anchored EB CFRP did lead to moderate increases in shear capacity compared to both control and unanchored EB CFRP strengthened beams.The authors gratefully acknowledge the help of the laboratory staff of University of Bath and University of Cambridge. The authors would also like to acknowledge the financial support of: the UK Engineering and Physical Sciences Research Council (under grants EPSRC EP/I018921/1 and EP/I018972/1); the Universities of Bath and Cambridge; and the project partners and sponsors – Parsons Brinckerhoff, Tony Gee and Partners LLP, Arup, Highways England, Concrete Repairs Ltd, LG Mouchel and Partners, The Concrete Society, Fyfe Europe S.A., Fibrwrap UK, Hughes Brothers and Ebor Concrete Ltd.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by ASCE

Behaviour of fabric-formed concrete beams reinforced with FRP bars

Casting non-prismatic optimised concrete beams in flexible fabric formwork can lead to a significant saving of concrete material and reduction of the embodied energy in concrete structures. It also offers the possibility to create interesting architectural features. However, the flexibility of this formwork may not allow an adequate control for ensuring the protective concrete cover, while the curvilinear profiles of such beams require a labour intensive pre-bending of the conventional steel reinforcement. Therefore, using Fibre Reinforced Polymer (FRP) materials as internal reinforcement in fabric-formed concrete beams might offer a number of advantages mainly in terms of avoiding the durability concern of steel corrosion. The light weight and flexibility of FRP bars, in addition, contribute to the overall low selfweight of the construction system and allow innovations such as supplying the FRP bars attached to the fabric and using the fresh concrete selfweight to pull down the bars into their design position without compromising the concrete cover. Nevertheless, reinforcing structurally optimised shallow beams with FRP bars is likely to result in large deflections and design governed by serviceability criteria. This paper presents the results of an experimental study on the structural behaviour of optimised fabric-formed beams reinforced with glass and carbon FRP bars. The use of self-compacting concrete is considered in order to aid the construction process. Other important aspects related to the structural design and predictability of deflections, such as the construction accuracy of fabric-formed beams, are also examined. © 2013, NetComposite Limited

Innovative reinforcement for fabric formed concrete structures

Using fabric formwork, it is possible to cast architecturally interesting, optimised structures that use up to 40% less concrete than an equivalent strength prismatic section, thereby offering significant embodied energy savings. This paper reports on the latest techniques for the design, optimisation and shape prediction of fabric formed concrete beams before new test results of an innovative anchorage method for both steel and fibre reinforced polymer longitudinal reinforcing bars are presented. Two 2m span beams were tested and the ‘helically confined splayed bar’ was shown to provide full anchorage in both cases. The two beams both exceeded their design capacity and showed remarkably similar behaviour at the serviceability limit state, with the steel reinforced section going on to display considerable ductility. Potential areas of future development are then highlighted, with the use of woven advanced composite fabrics as participating formwork for both beam and shell elements being of particular interest

Innovative reinforcement for fabric formed concrete structures

Using fabric formwork, it is possible to cast architecturally interesting, optimised structures that use up to 40% less concrete than an equivalent strength prismatic section, thereby offering significant embodied energy savings. This paper reports on the latest techniques for the design, optimisation and shape prediction of fabric formed concrete beams before new test results of an innovative anchorage method for both steel and fibre reinforced polymer longitudinal reinforcing bars are presented. Two 2m span beams were tested and the 'helically confined splayed bar' was shown to provide full anchorage in both cases. The two beams both exceeded their design capacity and showed remarkably similar behaviour at the serviceability limit state, with the steel reinforced section going on to display considerable ductility. Potential areas of future development are then highlighted, with the use of woven advanced composite fabrics as participating formwork for both beam and shell elements being of particular interest

Conservativeness in FRP-based structural strengthening design process

The fibre reinforced polymer (FRP) composites have proved to be effective for strengthening of existing concrete structures. However, the appraisal of the safety or conservativeness in the strengthening design process is more complex than it may first appear. This is due to the distinct characteristics exhibited by the FRP, such as lack of ductility and possibility of debonding-based failure modes. The conservativeness in particular context of the FRP-based strengthening design process is presented in this paper in the form that makes it possible to operate it mathematically. A comprehensive framework is presented that classifies the conservativeness involved in FRP-based structural strengthening into that applied on the material properties and that on the resistance contribution of the FRP. The conservativeness arising from same sources is presented in condensed form that makes it convenient to segregate and identify propagation of the conservativeness within the strengthening design process. The possibility of multiple failure modes of the externally-bonded FRP component is addressed through devising different conservativeness propagation paths, each representing a specific failure mode of FRP. It is shown that each of the possible conservativeness propagation paths is differently sensitive to the prescribed material conservativeness. Finally, the usefulness of the methodology in quantifying conservativeness is demonstrated for the case of FRP-based shear strengthening design process, for ACI440 and TR55 design guidelines. The methodology, however, can be applied to any guideline by appropriately calibrating it. The proposed methodology is a useful tool for fine-tuning and/or calibrating the design guidelines

Concrete structures using fabric formwork

Using fabric formwork, it is possible to cast architecturally interesting, optimised structures that use up to 40% less concrete than an equivalent strength prismatic section, thereby offering the potential for significant embodied energy savings in new concrete structures. This paper reports on the philosophy of and background to fabric formwork before techniques for the design, optimisation and shape prediction of fabric formed concrete beams are presented. The practicality of construction with non-orthogonal elements is discussed before the results of new structural test data, undertaken at the University of Bath on 4m span 'T' beam elements formed in reusable fabric moulds, are presented. Potential areas of future development for fabric formwork, including the use of woven advanced composite fabrics as permanent participating formwork and the feasibility of uniform strength prestressed beams, are then discussed. © J. J. Orr, A. P. Darby, T. J. Ibell, M. C. Evernden & M. Otlet

Nature is (a) mine: conceptions of nature in the Dutch ecogenomics community

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