Shear behaviour of fabric formed T beams reinforced using W-FRP

A combination of flexible moulds as external formwork and bespoke robotically fabricated fibre reinforced polymer cages as tensile reinforcement offers a new opportunity for the manufacture of structural concrete components that have been optimised to minimise material use. This technology could potentially help in our quest to reduce carbon emissions in the construction industry, yet there remain technical issues to overcome if such flexibly formed concrete structures are to become a reality. This paper presents experimental research on fabric-formed T beams reinforced with Wound Fibre-Reinforced Polymer (W-FRP) to quantify the shear contribution of this novel system. It is shown that, depending on the geometry of the beam, carefully chosen flexural and shear reinforcement can resist shear in a predictable manner. Because of geometric variation along the length of the beam, shear resistance is found to move from being provided by both the W-FRP reinforcement and the sloping longitudinal reinforcement to being provided predominantly by the longitudinal FRP reinforcement as the W-FRP gradually ruptures. In turn, this demands higher anchorage capacity of the longitudinal bars than that might have been expected by design codes of practice. By overcoming such issues, this paper shows that savings in concrete of up to 64% can be made in the webs in such structures, compared with conventional T-beams.EP/M020908/

Effectiveness of design codes for life cycle energy optimisation

The built environment is materially inefficient, with structural material wastage in the order of 50% being common. As operational energy consumption in buildings falls, due to continued tightening of regulations and improvements in the efficiency of energy generation and distribution, present inefficiencies in embodied energy use become increasingly significant in the calculation of whole life energy use. The status quo cannot continue if we are to meet carbon emissions reduction targets. We must now tackle embodied energy as vigorously as we have tackled operational energy in buildings in the past.Current design methods are poorly suited to controlling material inefficiency in design, which arises as a risk mitigation strategy against unknown loads and uncertain human responses to these loads. Prescriptive codes are intended to result in buildings capable of providing certain levels of performance. These performance levels are often based on small tests, and the actual performance of individual building designs is rarely fully assessed after construction. A new approach is required to drive the minimisation of embodied energy (lightweighting) through the collection of performance data on both structures and their occupants.This paper uses an industry facing survey to explore for the first time the potential use of performance measurement to create new drivers for lighter and more usable designs. The use of ubiquitous structural, human, and environmental sensing, combined with automated data fusion, data interpretation, and knowledge generation is now required to ensure that future generations of building designs are lightweight, lower-carbon, cheaper, and healthier

Fabric formed concrete: Physical modelling for assessment of digital form finding methods

Fabric formwork is a novel concrete construction method which replaces conventional prismatic moulds with lightweight, high strength sheets of fabric. The geometry of fabric formed structures is therefore dictated by the behaviour of fabric under hydrostatic loading. While there are numerous examples of digital and physical modelling of this problem, there have only been limited efforts to link the two through measurement. In this investigation, a number of small scale fabric formed beams were manufactured using both ‘free hanging’ and ‘keel mould’ methods, and the resulting forms were accurately measured with a digital 3D scanner. Computational form finding tools were also developed, enabling a comparison to be made between the predicted and build geometries. This allowed assessment of both the accuracy of the construction methods and the limitations of the form finding techniques used. The data collected provides a useful assessment of existing form finding techniques and will be used as a reference data set as these are developed further

A design methodology to reduce the embodied carbon of concrete buildings using thin-shell floors

This paper explores the potential of thin concrete shells as a low-carbon alternative to floor slabs and beams, which typically make up the majority of structural material in multi-storey buildings. A simple and practical system is proposed, featuring pre-cast textile reinforced concrete shells with a network of prestressed steel tension ties. A non-structural ll is included to provide a level top surface. Building on previous experimental and theoretical work, a complete design methodology is presented. This is then used to explore the structural behaviour of the proposed system, refi ne its design, and evaluate potential carbon savings. Compared to at slabs of equivalent structural performance, signi cant embodied carbon reductions (53-58%) are demonstrated across spans of 6-18m. Self-weight reductions of 43-53% are also achieved, which would save additional material in columns and foundations. The simplicity of the proposed structure, and conservatism of the design methodology, indicate that further savings could be made with future refinements. These results show that considerable embodied carbon reductions are possible through innovative structural design, and that thin-shell floors are a practical means of achieving this

Development of new FRP reinforcement for optimized concrete structures

With the goal of achieving sustainable design, being able to combine optimized geometries with durable construction materials is a major challenge for Civil Engineering. Recent research at the University of Bath has demonstrated that fibre-reinforced polymers (FRP) can be woven into geometrically appropriate cages for the reinforcement of optimised concrete beams. This innovative construction method enables the replacement of conventional steel with non-corrosive reinforcement that can provide the required strength exactly where needed. The manufacturing of the reinforcement is achieved by means of an automated process based on a filament winding technique. Being extremely lightweight, the wound-FRP (WFRP) cages are well suited to speeding up construction processes, as they can be delivered on site ready to be cast. In this paper, the results of flexural tests on optimised full-scale flexibly formed concrete elements are reported and discussed. Two different case studies are taken in consideration: A structurally optimized joist supporting a lightweight floor;A structurally optimized beam with an in-situ casting of a concrete floor. The optimization objective is to obtain the minimal mass of concrete required to achieve the structural capacity design requirements from widely recognized design codes. The experimental results demonstrate the reliability of the technical solution proposed and provide the basis of a new concept for sustainable and durable reinforced concrete structures

Design method of fabric formed concrete beams reinforced with W-FRP

Flexible moulds as external formwork and a novel robotically fabricated reinforcement, Wound FRP (W-FRP), provide the solution for the manufacture of complex structural concrete components being optimised to minimise material use and further reduce the carbon emissions from constructional industry. However, previous research has shown that the non-prismatic geometries and linear-elastic reinforcement could result in very different structural behaviours from the traditional concrete beams and invalidity of the existing codified design approaches. This research proposes revisions to the empirical equation to calculate the tensile force of inclined flexural reinforcement and a design method to predict the shear capacity of the W-FRP reinforced non-prismatic beams based on Modified Compression Field Theory (MCFT). A full-scale test of fabric formed T beam reinforced with W-FRP was conducted to demonstrate the validity of this new design approach. The research in this paper shows that: 1) the invalidity of the codified design approach could be attributed to the empirical calibration with prismatic beams; 2) geometry of the beam and the W-FRP shear reinforcement ratio are the main factors influence the flexural bar force development and 3) the proposed equation for calculating tensile force of flexural reinforcement could accurately predict the force development. This research provides a practical and valid approach for the future design of non-prismatic beams reinforced with W-FRP and addresses technical challenges in the way to minimising material use in concrete structures

Thin-shell textile-reinforced concrete floors for sustainable buildings

Steel-reinforced concrete, cast in flat prismatic forms, dominates multi-storey building construction around the world. Despite the fluidity of the material, opportunities to create efficient geometries through manipulation of form are habitually overlooked, resulting in inefficient cracked sections, high steel requirements and large carbon footprints. This project brings together modern developments in computational design, materials and construction to propose a novel thin-shell concrete flooring system for multi-storey buildings, creating a low embodied energy and lightweight alternative to traditional reinforced concrete flat slabs. In this investigation, the performance of various shell geometries are compared using finite element analysis. A functional design is produced and found to offer reductions of 62% in embodied energy and 64% in weight compared to an equivalent flat slab

Anchorage and residual bond characteristics of 7-wire strand

© 2017 Elsevier Ltd The periodic assessment of our existing concrete infrastructure is a crucial part of maintaining appropriate levels of public safety over long periods of time. It is important that realistic predictions of the capacity of existing structures can be made in order to avoid unnecessary and expensive intervention work. Assessment is currently undertaken using codified models that are generally readily applied to infrastructure with simple geometric and reinforcement details that conform to design methods for new structures. This approach presents two significant challenges for prestressed structures: (1) design and construction practice has changed significantly in the past 50 years, and modern codified approaches can be incompatible with historic structures; and (2) deterioration of exposed soffits can lead to reduced cover to internal prestressing strand. Unless appropriate reductions are used in assessment of a structure with such problems, unnecessary load restrictions, or major strengthening or reconstruction work may be required, despite having carried a full service load since its construction. There are currently no widely accepted methods for the prediction of peak and residual capacities in prestressed concrete beams with inadequately detailed 7-wire strand. This paper presents a completely new prediction methodology, validated against new experimental results from 31 novel semi-beam tests. The proposed models for peak load, residual load, and bond stress-slip modelling provide reliable, accurate, and conservative results. Their results demonstrate feasible and appropriate capacity reduction factors for use in the assessment of existing concrete infrastructure

Genetic and environmental influence on foliar carbon isotope composition, nitrogen availability and fruit yield of 5-year-old mango plantation in tropical Australia

The aim of this study was to quantify the effect of different varieties, planting densities, tree training systems and canopy aspect (north and south) on tree water use efficiency and nitrogen (N) availability in relation to mango fruit yield and fruit size as well as soil fertility (particularly total carbon (C) and total N as well as C and N isotope compositions) in a 5-year-old mango plantation of tropical Australia