Design, Construction and Testing of a Low Carbon Thin-Shell Concrete Flooring System

Abstract

Rapid global urbanisation and population growth is driving unprecedented levels of building construction, with the total worldwide floor area expected to almost double over the next 40 years. Since most of the structural material in a building exists within the floors, these present a significant opportunity for structural engineers to contribute to a more sustainable construction industry. This paper examines a novel flooring system of textile-reinforced concrete shells with a foamed concrete fill, which has the potential to halve the amount of materials in a building's entire structure. A new design and geometry optimisation method is described, as well as the construction and testing of two prototypes; each 18mm thick, 2m in span and 200mm tall.These textile-reinforced concrete shells are unconventional in their low total depth, low reinforcement content and lack of rigid supports. Both were reinforced with AR-glass fibre textile and constructed using fine-grained concrete, however only one featured a foamed concrete fill. Each was tested to destruction under an asymmetric load. In both cases, a hinged collapse mechanism was formed rather than sudden catastrophic failure, with positive implications for safety and robustness.A non-linear finite element model was developed which replicated the observed behaviour well, including cracking patterns. Inaccuracies in geometry arising from the hand-made construction methods were measured and their structural impact was assessed and found to be small.The investigations confirm the strength, robustness and buildability of the structural system, and establish a reliable analysis method.

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

“…These have been previously shown to have only a minor inuence on the predicted deformation in this application, through a direct comparison between linear and non-linear models [30]. Buckling also cannot be assessed by a linear model, although again this has been shown not to be critical in this application in previous publications, using both non-linear FE analysis and physical testing [29,30]. Linear analysis ignores redistribution of peak forces caused by cracking and crushing, which is conservative in the context of the lower-bound design approach described in Section 2.5 of this paper.…”

“…In addition, the ll provides vibration damping, thermal insulation and acoustic absorption. In a previous study [29], two prototype shells were constructed and tested, with and without a foamed concrete ll of 800kg/m 3 density. The inclusion of the ll was found to have only a small eect on strength and stiness, and can therefore be conservatively ignored in analysis.…”

“…It has been shown previously [27,30] that minimising bending strain energy has positive implications for structural performance, by maximising stiness, natural frequency and buckling resistance whilst reducing the strength requirements of the TRC section and, correspondingly, material quantities. The tness landscape is smooth across these three parameters (a, b and "), with a single global minimum, ensuring reliable optimisation [29].…”

“…This paper begins by introducing a proposed structural system and corresponding design methodology, building upon previous publications [27,28,29,30], which is veried through comparison with experimental tests. Once established, this methodology is used to further rene the design and compare its performance with at slabs, enabling embodied carbon savings to be quantied.…”

Automated Framework for the Optimisation of Spatial Layouts for Concrete Structures Reinforced with Robotic Filament Winding

“…However, short fibres do not reinforce specific directions to carry high local tensile stresses based on an optimised layout. Reinforcement mats can carry higher tensile stresses, but the use of non-optimal, homogeneous and orthogonal meshes demands more material, and their placement is hard to automate, requiring patching and overlapping to map large-span plates or shells with double curvature [8,9]. High, local, oriented tensile capacity can be provided by long fibres, or filaments [10].…”