Fostering innovative and sustainable mass-market construction using digital fabrication with concrete

Bischof, Patrick; Mata‐Falcón, Jaime; Kaufmann, Walter

doi:10.1016/j.cemconres.2022.106948

Cited by 34 publications

(23 citation statements)

References 43 publications

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“…Table 3 elaborates on characteristics (i) inherent to the choice concerning the cross-section of floor systems and (ii) deemed necessary to discuss the potential and challenges of ribbed floor systems. The current share of the different floor types developed through the last century depends on tradition and market-specific reasons, such as the availability of material and workforce, architectonic individualism, requirements on building systems, or the available infrastructure for on-site or prefabricated construction [3]. Flat slabs, T-beams, and hollow-core-slabs are the most frequently applied floor systems.…”

Section: Concrete Floor Systemsmentioning

confidence: 99%

“…For showcasing the slab design, a full-scale column-slab segment was fabricated (Figure 7c) with the following steps: (i) printing of the rib formwork with FDM, including reinforcing bars crossing the formwork on the printing platform (as suggested in [3]); (ii) adding prefabricated reinforcement cages for the ribs; (iii) closing the ribs by 3D printing the 'roof' formwork (Figure 7b); (iv) casting the ribs;…”

Section: D Printed Polymeric Slab Formworkmentioning

confidence: 99%

“…With slab elements being produced upside down, this concept requires prefabrication as the slab must be turned over after production. While the flipping process might be risky, on-site connections of partially or fully prefabricated elements are essential to employ such solutions reliably [3]. At the same time, this concept benefits from the limited casting height of concrete, allowing the use of conventional concrete, albeit with stiffeners integrated into the formwork (Figure 7b).…”

Section: D Printed Polymeric Slab Formworkmentioning

confidence: 99%

“…75% in Switzerland [2]). Floor slabs constitute 40%...60% of the concrete volume within typical three to eight-storey buildings, while the foundations account for 20%...30% [3]. With increasing building height, the share of floor slabs increases compared to that of the foundations.…”

Section: Introductionmentioning

confidence: 99%

“…Despite its relevance, environmental sustainability is not the only requirement floor slabs need to fulfil. Bischof et al [3] suggested six main criteria that buildings and infrastructure need to comply with today: (i) structural safety, (ii) durability, (iii) serviceability, (iv) aesthetics and integration, (v) environmental sustainability and (vi) construction efficiency. Table 1 elaborates on these criteria with corresponding descriptions.…”

Section: Introductionmentioning

confidence: 99%

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Digitally fabricated ribbed concrete floor slabs: a sustainable solution for construction

et al. 2022

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The concrete used in floor slabs accounts for large greenhouse gas emissions in building construction. Solid slabs, often used today, consume much more concrete than ribbed slabs built by pioneer structural engineers like Hennebique, Arcangeli and Nervi. The first part of this paper analyses the evolution of slab systems over the last century and their carbon footprint, highlighting that ribbed slabs have been abandoned mainly for the sake of construction time and cost efficiency. However, highly material-efficient two-way ribbed slabs are essential to reduce the environmental impact of construction. Hence, the second part of this paper discusses how digital fabrication can help to tackle this challenge and presents four concrete floor systems built with digitally fabricated formwork. The digital fabrication technologies employed to produce these slab systems are digital cutting, binder-jetting, polymer extrusion and 3D concrete printing. The presented applications showcase a reduction in concrete use of approximately 50% compared to solid slabs. However, the digitally fabricated complex formworks produced were wasteful and/or labour-intensive. Further developments are required to make the digital processes sustainable and competitive by streamlining the production, using low carbon concrete mixes as well as reusing and recycling the formwork or structurally activating stay-in-place formwork.

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Section: Concrete Floor Systemsmentioning

confidence: 99%

Section: D Printed Polymeric Slab Formworkmentioning

confidence: 99%

Section: D Printed Polymeric Slab Formworkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Digitally fabricated ribbed concrete floor slabs: a sustainable solution for construction

et al. 2022

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Structural design and testing of material optimized ribbed RC slabs with 3D printed formwork

Huber

Burger

Mata‐Falcón

et al. 2023

Structural Concrete

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Most of the concrete volume in multistorey buildings is cast in solid slabs, which are frequently flat slabs supported on columns. By using two-way spanning ribbed slabs, concrete consumption could be significantly reduced. However, due to the high costs associated with formwork, such a complex rib configuration is rarely used nowadays. With the advent of technologies for automated formwork fabrication, the material-saving potential inherent in this structural system could again be exploited. This paper investigates the feasibility of material-efficient ribbed concrete slabs on a building scale using conventional concrete and steel reinforcing bars cast inside a three-dimensionalprinted plastic-based formwork. To that end, the code-compliant design of ribbed slabs is first discussed, followed by the introduction of a concept for an automated design-to-production workflow. The sustainability of this slab system is compared to a solution using conventional formwork in a case study consisting of a multibay office building with slabs spanning 8 m in both directions, revealing that ribbed slabs use 40% less concrete than solid slabs. Several representative structural elements of the case study (ribs, slab-column transition) were produced at full-scale and tested until failure to investigate the feasibility of production and structural performance. Three T-beams with various rib shapes (straight, kinked with diaphragms, curved) were tested in a threepoint bending configuration, showing a ductile behavior with longitudinal reinforcement yielding and indicating the relevance of torsional effects in curved ribs. Punching tests on two slab-column connections (ribbed, solid) revealed that the optimized ribbed slab could prevent brittle punching failures and achieve an ultimate load 105% higher than the solid reference slab. All specimens' load-bearing behavior could be predicted using established design formulas, showing the feasibility of producing code-compliant ribbed slabs with the applied technology.Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.

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Digitally fabricated weak interfaces to reduce minimum reinforcement in concrete structures

Bischof

Mata‐Falcón

Ammann

et al. 2022

Structural Concrete

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Crack initiators in reinforced concrete structures can facilitate fulfilling the serviceability requirements. They can be used as a design parameter to diminish the minimum reinforcement for members subject to imposed deformation and exposed to the environment as they reduce the crack spacing and width when arranged close enough. While crack initiators in conventional concrete construction are cumbersome to provide (e.g., by construction joints or taperings), they are inherent to layered extrusion processes with digital fabrication technologies: the tensile strength is typically reduced locally in interfaces between layers. Rather than trying to avoid these weak interfaces, this paper discusses the potential of taking advantage of them to act as crack initiators reducing the minimum reinforcement content. A tension chord-based model is developed to (i) account for the local strength reduction and (ii) predict the effect of weak interfaces on the expected crack spacing and width. As a key finding, the model predicts a reduction of the required minimum reinforcement ratio proportional to the locally decreased concrete tensile strength for a specified maximum crack width requirement under imposed deformations. An experimental campaign on five layered and three reference tension ties confirmed the clearly positive impact of weak interfaces on crack spacings and widths.

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Fostering innovative and sustainable mass-market construction using digital fabrication with concrete

Cited by 34 publications

References 43 publications

Digitally fabricated ribbed concrete floor slabs: a sustainable solution for construction

Digitally fabricated ribbed concrete floor slabs: a sustainable solution for construction

Structural design and testing of material optimized ribbed RC slabs with 3D printed formwork

Digitally fabricated weak interfaces to reduce minimum reinforcement in concrete structures

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