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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...
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... has relatively low embodied energy but is used in vast quantities: in 2008 world production of cement was approximately 2.8x10 9 metric tons 3 (2.8x10 12 kg) and its manufacture accounted for almost 3% of global CO 2 emissions 4 , suggesting that concrete should be cast in optimised structures. Fabric formwork at last provides a suitable method to achieve these reductions by facilitating the production of variable section members (Figure 1). Concrete volume savings of up to 40% 5,6 are feasible and the use of fibre-reinforced polymers as either internal or external reinforcement presents exciting new opportunities for the practical use of fabric formwork. ...
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... material properties for both beams (as measured prior to testing) are provided in Table 1 and salient dimensions of the beams, which vary in both cross section and elevation, are provided in Figure 9. The beams were constructed in a hanging hessian fabric mould that was fixed in posi- tion along two line supports, with the 'T' section created using curved timber formers, as shown in Figure 10. Construction methods for fabric formed beams are discussed in fur- ther detail elsewhere 2 . ...
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... an approximately linear initial load-displacement response, Beam 1 exhibited considerable ductility before failing at a total load of 26kN (5.85kips). Flexural cracking, as shown in Figure 12(l), was considerable, and failure occurred due to crushing of the compression zone after the longitudinal steel had yielded. Cracking was well distributed along the length of the beam, indicating a constant stress in the bar, as expected by merit of the design procedure used. ...
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... "14"&56003%$5 Beam 2 ( Figure 13) displayed a similar response to Beam 1 in the serviceability condi- tion, yet failed in a more brittle diagonal tension mode close to the supports after display- ing some flexural cracking in the main span. A wide inclined crack opened up close to the roller support at a total load of approximately 27kN (First Peak, Figure 13). ...
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... Beam 2 ( Figure 13) displayed a similar response to Beam 1 in the serviceability condi- tion, yet failed in a more brittle diagonal tension mode close to the supports after display- ing some flexural cracking in the main span. A wide inclined crack opened up close to the roller support at a total load of approximately 27kN (First Peak, Figure 13). Load was then reapplied and the beam reached a second peak of 25kN before complete failure of the CFRP bar occurred. ...
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... was then reapplied and the beam reached a second peak of 25kN before complete failure of the CFRP bar occurred. Analysis of the beam revealed that the splayed anchor had slipped by less than 1mm and that failure occurred after the CFRP bar ruptured at the po- sition of the inclined crack, as shown by the photographs in Figure 14. The load dis- placement responses of both beam tests are shown in Figure 15, where a reduction in stiffness is seen in Beam 2 under re-loading. ...
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... of the beam revealed that the splayed anchor had slipped by less than 1mm and that failure occurred after the CFRP bar ruptured at the po- sition of the inclined crack, as shown by the photographs in Figure 14. The load dis- placement responses of both beam tests are shown in Figure 15, where a reduction in stiffness is seen in Beam 2 under re-loading. Figure 15 illustrates that the serviceability behaviour of both beams was very similar, as was their peak load capacity. ...
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... load dis- placement responses of both beam tests are shown in Figure 15, where a reduction in stiffness is seen in Beam 2 under re-loading. Figure 15 illustrates that the serviceability behaviour of both beams was very similar, as was their peak load capacity. Beam 1 displayed an ideal failure mode, moving from almost linear elastic to perfect plastic behaviour after the section cracked. ...
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... (4) In a hypothetical, fully bonded section the strain in the longitudinal reinforcement and its surrounding concrete are the same. At the onset of cracking, local strains in the bar increase rapidly and since fibre reinforced polymer bars are unable to yield and maintain compatibility by stretching plastically, they will fail as soon as a limiting strain capacity is reached 18 (Figure 16). Conversely, in a section with zero bond between the bar and concrete, strains in the reinforcement are low since it is able to move relative to the con- crete and whilst failure due to high local strains may now be prevented, lower strains in the reinforcement limit the moment capacity of the section. ...
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... larger structures, or to satisfy the requirements of reinforced concrete design codes, the provision of shear reinforcement may become a necessity, yet the provision of such reinforcement to a continuously varying cross section has the potential to add signifi- cantly to construction costs. The use of a participating fabric formwork system, in which the fabric acts as both formwork and reinforcement, may therefore be advantageous (Fig- ure 17). Advanced composites could allow the designer to simply specify weave direc- tions and densities at various critical points along the length of a beam based on the ap- There are, however, a number of technical hurdles to clear before such a method could be used in general construction. ...
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... prestressed structures the use of high and ultra-high performance concrete becomes increasingly advantageous, allowing long span beams to be cast with minimal cross sec- tional areas and potentially excellent behaviour at the ultimate and serviceability limit states. The use of ultra-high performance concrete in fabric formed concrete structures (Figure 18(r)) is a further part of ongoing research at the University of Bath. ...
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... work is required in the use of flexible carbon fabrics and grids as both external participating reinforcement in beam structures and as internal reinforcement in thin-shell elements. A summary of the reinforcement opportunities and challenges for fabric formed concrete beams is provided in Figure 21. Fabric formwork provides an innovative construction method that has the potential to significantly reduce material use in the construction industry. ...
Citations
... The logical continuation of the exploration of fabric formwork was the integration of the reinforcement function within the formwork itself (e.g. [36,37]). In a way, this process revisits the principles of the Cottancin and Lilienthal systems [38] with modern technologies, enabling the fabrication of non-prismatic beams with low thicknesses of concrete covers. ...
... Shape optimisation is a proven strategy to reduce material usage by providing the necessary amount of material in the right places. Orr et al. [177,172] and Garbett et al. [80] demonstrated the use of fabric as a formwork to cast concrete beams in optimised shapes. Hawkins et al. [102] reviewed that shape optimisation using flexible formwork can reduce concrete consumption in beams by up to 44%. ...
... According to Orr et al. [177], the depth profiles of the shape optimised beams can be developed considering the flexural performance, and the width profile can be developed considering shear performance. Some adjustments to the depth profile might be required to incorporate shear capacity. ...
... The designs discussed are achievable using flexible fabric formwork and bending steel rebar into the required shapes. Participating fabric formwork that functions as both reinforcement and formwork can therefore bring additional benefits [177]. Fibre composite fabrics that can be tailored for the design requirements considering fibre densities and alignment can theoretically achieve the required structural performance. ...
Limiting global warming has become an internationally agreed target to stop the rapid and devasting consequences of climate change. Though reducing CO2 emissions is the path forward, a substantial component of the emissions stems from the processes related to the construction industry. The manufacture of cement alone accounts for 6% of global CO2 emissions. A significant challenge arises as CO2 reduction objectives must be achieved alongside the increasing demand for infrastructure caused by rapid urbanisation. This thesis explores how exploring different design solutions by varying design parameters, analysing alternative construction forms, and optimising shapes can reduce the embodied carbon of steel-reinforced concrete floors. Four interconnected optimisation studies are illustrated in this thesis: (1) shape optimisation of reinforced concrete beams using a parametric design approach to achieve practical and technically feasible solutions, considering deflection performance; (2) parametric optimisation for reinforced concrete flat slabs, coupled with a finite element model to estimate non-linear long-term deflections; (3) simultaneous optimisation of the cost and carbon emissions of concrete floors using different conventional slab designs; and (4) comparing the potential carbon savings of different optimisation strategies for concrete floors against the timeline for potential implementation. Possible variations of the optimisation outcomes depending on the selected embodied carbon coefficients and cost rates are also analysed. Shape optimised construction methods offer solutions with the minimum embodied carbon for a given set of design criteria in the long term. In the ascending order of possible reductions in embodied carbon, concrete floors can be optimised in the short term by: (1) minimising section depth to satisfy deflection limitations; (2) adopting low-strength concrete in flexural members; (3) analysing conventional alternative slab types; and (4) optimising column layouts. Nonlinear relationships observed in optimisation methods highlight key design aspects to target for maximum reductions in embodied carbon. The conclusions reached herein are presented as a set of guidelines for structural engineers to minimise the embodied carbon of concrete floor designs.
... Block Research Group (BRG) (BRG 2012) explored the fundamental analysis and design of geotextile or coated fabric made formworks. Orr et al. (2011b) and Orr (2012) presented fabric formed concrete beams shape prediction method and optimization procedure. Also, Orr et al. (2012a) illustrated some methods for the optimized design of ultra-high performance fiber reinforced concrete elements using fabric formwork and structural tests. ...
... Each application of flexible formwork has its own unique form-finding requirements, and 594 the complexity of the analysis can often be reduced by making appropriate simplifying 595 assumptions. For example, a stiff or lightly stressed formwork material may be modelled 596 as inextensible, or a three dimensional object can be simplified as a series of two 597 dimensional sections in some cases [133]. 598 ...
Concrete is the most widely used construction material. Worldwide consumption of cement, the strength‐giving component in concrete, is now estimated to be 4.10 Gt per year, having risen from 2.22 Gt just 10 years ago. This rate of consumption means that cement manufacture alone is estimated to account for 5.2 % of global carbon dioxide emissions.
Concrete offers the opportunity to create structures with almost any geometry economically. Yet its unique fluidity is seldom capitalized upon, with concrete instead being cast in rigid, flat moulds to create non‐optimized geometries that result in structures with a high material usage and large carbon footprints. This paper will explore flexible formwork construction technologies that embrace the fluidity of concrete to facilitate the practical construction of concrete structures with complex and efficient geometries.
This paper presents the current state of the art in flexible formwork technology, highlighting practical uses, research challenges and new opportunities.
... Such a method of anchoring allows one not only to locally increase the bonding area between the composite rod and the potted material, but also to change the conditions of transfer of the external tensile load. This design solution can also be used as an end anchorage in the tensile part of concrete structures to prevent the slippage of rebars after the cracking of concrete [7]. ...
A finite element analysis is carried out to determine the stress-strain state of anchors for round rods made of a high- modulus, high-strength unidirectional carbon-fiber reinforced plastic. The rods have splitted ends in which Duralumin wedges are glued. Three types of contact between the composite rods and a potted epoxy compound are considered: adhesion, adhesion-friction, and friction ones. The corresponding three-dimensional problems in the elastic statement are solved by the finite-element method (FEM) with account of nonlinear Coulomb friction. An analysis of stresses on the surface of the composite rod revealed the locations of high concentrations of operating stresses. The results of FEM calculations agree with experimental data.
