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Structural Behaviours of a Concrete Façade Panel Prototype Facilitated by 3D Printed Formwork
Abstract
Façades are key building components, determining building performance and forming the interface between inhabitants and the general public. Accordingly, façades should integrate high aesthetic value with the capability to bear relevant loads. Contemporary architectural façade design strategies often employ complex shapes, which presents civil engineering challenges in terms of assessing structural performance as well as determining effective fabrication strategies. Using 3D concrete printing for fabrication can achieve freeform shapes but has several limitations including limited structural performance. Instead of directly 3D printing concrete elements, this paper presents an approach to fabricating geometrically complex façade elements in ultra-high-performance fibre-reinforced concrete using 3D printed formwork to achieve greater accuracy and cost efficiency compared to conventional fabrication methods. Following compression test and flexural test to examine the feasibility of using 3D printed formwork for concrete fabrication, a façade prototype with a non-standard shape using 3D printed polymer formwork and UHPFRC is examined for its structural behaviours. Results show that compressive strength and flexural strength are not affected negatively by the exterior 3D printed formwork. Meanwhile, the proposed façade prototype demonstrates good concrete flowability and load test results, promising a new construction method for concrete fabrication.
... Image: authors (UHPC) to mold modular kite panels. This material offers the durability and finish required for architectural elements exposed to environmental conditions (Gao et al. 2023;Harsono et al. 2023). This modular approach ensures consistent quality and streamlines the installation, reducing costs and enhancing efficiency for large-scale construction projects (Laufs and Nefedov 2019;Zhuang et al. 2023). ...
This study investigates the development of the Hat monotile, a singular tile designed by David Smith and his team, capable of covering surfaces with unique, non-repeating, aperiodic patterns. We enhance this tiling concept by integrating diverse motifs into the Hat monotile, improving its attractiveness and adaptability. Utilizing computational tools, we experiment with these tiles to assess their potential in architecture, specifically focusing on their ability to innovate facade designs through simplified fabrication processes, cost reduction, and greater design flexibility. Our research demonstrates the practical applications of these distinctive patterns, bridging the gap between mathematical theories and architectural implementation. The objective is to encourage further exploration and innovation in applying aperiodic patterns, underlining their potential to discover the beauty in asymmetrical forms.
... Many research studies used bespoke 3DPF where the formwork has been destroyed with a heat gun (Jipa et al. 2019), stayed in place (Aghaei-Meibodi et al. 2018), or dissolved (Sitnikov 2019). Another study used PETG formwork for casting one unit façade element (Gao et al. 2024). However, the 3DPF needs is used multiple times which is compatible with the economics of scale. ...
3D printing formwork (3DPF) is a leading method for enhancing the surface quality of precast elements while creating custom complex geometries. Bespoke fabrication methods for 3DPF are incompatible with economic scalability. With increasing awareness of circular economy principles and a growing interest in complex geometric elements, there is a need to explore the design of reusable 3DPF for casting of intricate precast elements. Topological interlocking assemblies (TIA) which are compatible with reversible assembly practices, present an opportunity to design individual blocks with complex curvatures allowing for mortarless assembly. A studio project tasked students with designing TIA blocks and reusable 3DPF for casting them. The project produced installations demonstrating proof-of-concepts for 3DPF for repeated casting of precast blocks. The results bridge the gap between geometric complexity in precast elements and the additively manufactured reusable molds for casting them.
The average academic programs appear not to contain sufficient elements in favor of computational methods, which remain strongly ghettoized in important modules like design studios in Architecture and structures modules in Engineering. Undergraduate programs are extremely hard to change due to the educational frameworks. Several authors have discussed the difficulties of embedding digital strategies and techniques within the academic realm, even with a specific focus to Architecture. Extra-curricular activities ranging from Parametric Design to BIM, to more appealing technologies such as AI and Robotic Fabrication, have been organized in response to the need for innovation. The paper illustrates the outcomes of a series of teaching activities carried out to frame needs and solutions in Architecture pedagogy. The paper discusses new educational trends which will foster enhanced and sustainable design processes and built environment.
Concrete is a material favored by architects and builders alike due to its high structural strength and its ability to take almost any form. However, to shape concrete structures, heavy-duty formwork is usually necessary to support the fresh concrete while curing. To expand geometrical freedom, three-dimensional (3D) printed concrete formwork has emerged as a field of research. This article presents one possible application, a novel fabrication process that combines large-scale robotic fused deposition modeling 3D printing with simultaneous casting of a fast-hardening, set-on-demand concrete. This fabrication process, known as ''Eggshell,'' enables the production of nonstandard concrete structures in a material-efficient process. By casting a fast-hardening concrete in a continuous process, lateral pressure exerted by the fresh concrete is kept to a minimum. In this way, a 1.5-mm-thin thermoplastic shell can be used as a formwork, without any additional support. Geometries of different scales are tested in this article to evaluate the feasibility of the Eggshell fabrication process in an architectural context. An array of printing materials are also tested, and several different reinforcement concepts are analyzed. The findings are used to produce a full-scale architectural demonstrator project. This article shows that a wide range of concrete geometries can be produced in a material-efficient fabrication process, paving the way toward mass customization and structural optimization within concrete architecture.
3D Construction Printing (3DCP) is a new and emerging technology that is set to revolutionise construction. Currently the technology is in its early stages of development and many hurdles are yet to overcome. Particularly in the field of extrusion 3DCP with cementitious materials, one of the primary hurdles is the weak interface bonds. The weakness in bonds is hypothesised to be present due to the layered fabrication of a stiff cementitious mix that creates a localised void structure. Due to the time gap intervals between depositions, the bond strength decreases due to lack of intermixing. This paper seeks to explore a method to strengthen the interlayer bonds, by applying a cementitious paste at the interface, to minimise voids and promote bond area. Using a flatbed scanner and a unique method of image processing on printed colour layers, a quantitative evaluation of the contact area, “effective bond” area, was determined. The application of these experimental and analytical methods shows that an increase in bond strength is achieved, which is proportional to the effective bond area.
Submillimetre Formwork is a novel method for fabricating geometrically complex concrete parts with 3D printed plastic formwork (Figure 1). This research investigates how 3D printing can be used to fabricate submillimetre-thin formwork. To achieve this, computational methods for optimizing the fabrication speed of formwork with plastic deposition 3D printing are developed, as well as methods to stabilize the minimal formwork during the casting process. Without any coating and post-processing steps, the plastic formwork is easily removable, recyclable and biodegradable. The implications of Submillimetre Formwork are a considerable material reduction, faster off-site fabrication time for the formwork, ease of transportation to site, ease of on-site assembly and unprecedented design opportunities for free form and highly detailed concrete components. Figure 1. Prototype for an architectural concrete element cast in Submillimetre Formwork. DBT, ETH Zűrich, 2017
An advancing technology that combines the concrete extrusion with a motion control to create structures with complex geometrical shapes without the need for formwork is known as 3D concrete printing. Since this technique prints layer by layer, the time taken to reach the same position in the subsequent layer is important as it will create an anisotropic property that has a weaker tensile strength at the bond interface of the two printed filaments. Through rheological measurement, which reveals the material deformation and flow behaviour, it is possible to examine the material structural build-up due to time-gap effect by measuring at different time delay. This paper focuses on investigating the time-gap effect on the printed filament with rheological and observation at macroscopic-scale to understand the material behaviour of the initial and subsequent printed layer during its fresh phase. Rheological experiment findings reveal that the tensile strength of the printed specimen is correlated to the material modulus at the initial layer.
This paper presents the first stage of a study examining the digital design and fabrication of a parametrically defined sculptural concrete façade element employing fibre reinforced concrete. On the background of a literature review of related precedent studies, the paper extends the scope of previous studies by offering a detailed insight into the process of integrating architectural considerations with material properties of fibre reinforced concrete, detailed structural analysis and construction constraints. The paper offers technical details with a focus on material to similar ongoing studies.
The imperative need for complex geometries in architecture is driving innovation towards an unconstrained fabrication freedom in building components. Fabrication constraints are a critical obstacle when material efficiency through complex, optimized topologies is sought. To address this constraint, this research investigates the use of 3D printed plastic formwork for fibre reinforced concrete at large scale. This novel construction method makes complex topologies and precise details possible for full-scale, load bearing structures. To demonstrate its potential applications, SkelETHon —a functional four-meter-long concrete canoe— was designed, built and raced in a regatta on the Rhine river.
Fiber reinforced concrete (FRC) has been widely used due to its perfect mechanical performance, but inclusion of fibers has a decisive influence on the fresh properties. Workability as a short-term property is expected to affect long-term properties of concrete. In this paper, the definition of workability, rheological models of FRC, measurement methods of workability and rheological properties, as well as the measure techniques of the fiber orientation and distribution were discussed in detail. This paper presents a complete and updated literature review on the effects of fiber, various constituent, mixing and temperature on the fresh and rheological characteristics. It also reveals the relationship between workability, rheological properties and mechanical performance of FRC. Most importantly, the paper discusses plausible strategies to control rheological properties of FRC, which makes workability and mechanical performance of FRC simpler and more predictable.
This study investigated 3D concrete printing of permanent formwork for concrete column construction. The effect of different hydroxypropyl methyl cellulose (HPMC) contents (0, 0.0003 and 0.0006 by mass of binder) and the water-to-binder (W/B) ratios (0.27, 0.29 and 0.31) on the rheological properties, structural build-up and mechanical performance were studied using several mixtures for manufacture of the permanent formworks. The results showed that the mixture with the HPMC = 0.0006 and the W/B = 0.27 showed the maximum static yield stress, largest thixotropy and maximum green strength, and thereby selected as the optimum mixture. The plastic failure of the optimum mixture was also predicted using a thixotropy model and was compared with the experimental results. Subsequently, three concrete columns with different longitudinal steel reinforcement ratios (0.0%, 1.9% and 2.5%) were constructed using the printed concrete as the permanent formwork and tested in compression. Good bonding was observed at the interface of the cast-in-place concrete and the printed concrete permanent formwork. In addition, it was observed that the initial stiffness, the maximum bearing capacity and the corresponding longitudinal displacement of the concrete columns increased, as the longitudinal reinforcement ratio increased. The counterpart concrete columns using the conventional formworks were also constructed and tested for comparison. In comparison, the concrete columns made using the printed concrete as the permanent formwork obtained a higher stiffness and bearing capacity than the counterpart conventional concrete columns. The reasons for the differences are explained.
After 35 years of development, 3-D printing is slowly entering civil engineering research programmes.
The majority of civil engineering research effort is focused on 3-D printing of fresh concrete mix. 3-D
printed concrete is limited by weak bonding between printed layers of concrete and lack of reinforcement.
Authors propose a different approach for utilization of 3-D printing in civil engineering. 3-D
printed plastic formworks for concrete with internal elements substituting steel reinforcement is a
way to go. Mechanical characteristics of 3-D printed plastics is much weaker than characteristics of steel
but an unconventional internal shape of formwork and the influence of a 3-D printed formwork itself can
substitute much of the weaker mechanical characteristics of a plastic
Building façades play an important role in building aesthetics and in protecting the structural system and contents from deterioration due to exposure to an aggressive environment. Well-designed façades can also help improve the durability and energy efficiency of the building as well as elevating the level of human comfort. In general, façade design and detailing have not received the same level of rigor and overall scrutiny as the load-bearing components of buildings. Current codes and standards require safety provisions for environmental separating elements of a building. However, there is an urgent need for the development of detailed procedures for the design of durable and sustainable building façades. This paper reviews the needed considerations in each stage of an optimal façade life cycle and compares them with the current available practices and discusses various safety-related issues, failure modes, and the risks involved throughout the system service life.
The emphases on reduction of construction time and production costs have profound
influences on the construction process that has led us to investigate a new
paradigm, known as 3D concrete printing. This technique can fabricate complex 3D
building components directly from computer aided design models without any tooling
and human intervention. However, compatibility of the presently available materials
has impeded its widespread application and commercialization. This paper introduces
an overview of concrete printing processes and its noteworthy potentials
in the building and construction sector. After sketching the potential, a novel fly ash
based inorganic geopolymer is printed and characterized in terms of fresh and
hardened properties with an aim for sustainable built environment.
In the current contribution for the first time a mechanistic model is presented that can be used for analysing and optimising the mechanical performance of straight wall structures in 3D printing processes. The two failure mechanisms considered are elastic buckling and plastic collapse. The model incorporates the most relevant process parameters, which are the printing velocity, the curing characteristics of the printing material, the geometrical features of the printed object, the heterogeneous strength and stiffness properties, the presence of imperfections, and the non-uniform dead weight loading. The sensitivity to elastic buckling and plastic collapse is first explored for three basic configurations, namely i) a free wall, ii) a simply-supported wall and iii) a fully-clamped wall, which are printed under linear or exponentially-decaying curing processes. As demonstrated for the specific case of a rectangular wall lay-out, the design graphs and failure mechanism maps constructed for these basic configurations provide a convenient practical tool for analysing arbitrary wall structures under a broad range of possible printing process parameters. Here, the simply-supported wall results in a lower bound for the wall buckling length, corresponding to global buckling of the complete wall structure, while the fully-clamped wall gives an upper bound, reflecting local buckling of an individual wall. The range of critical buckling lengths defined by these bounds may be further narrowed by the critical wall length for plastic collapse. For an arbitrary wall configuration the critical buckling length and corresponding buckling mode can be accurately predicted by deriving an expression for the non-uniform rotational stiffness provided by the support structure of a buckling wall. This has been elaborated for the specific case of a wall structure characterised by a rectangular lay-out. It is further shown that under the presence of imperfections the buckling response at growing deflection correctly asymptotes towards the bifurcation buckling length of an ideally straight wall. The buckling responses computed for a free wall and a wall structure with a rectangular lay-out turn out to be in good agreement with experimental results of 3D printed concrete wall structures. Hence, the model can be applied to systematically explore the influence of individual printing process parameters on the mechanical performance of particular wall structures, which should lead to clear directions for the optimisation on printing time and material usage. The model may be further utilised as a validation tool for finite element models of wall structures printed under specific process conditions.
This paper presents a numerical investigation on assessing whether the concrete damage plasticity (CDP) constitutive model can be used to simulate new ultra-high performance fibre reinforced concrete (UHP-FRC) material under impact loading rates at different damage stages. The performance of the numerical models is verified by comparing numerical results to the experimental data that were previously tested by the authors. This paper also presents experimental tests that aimed to characterize the strain rate effect on UHP-FRC. The numerical simulations have been performed using ABAQUS/Explicit. CDP parameters are identified based on impact test results of a control specimen. Subsequently, the predictive capability of calibrated model has been investigated by simulating two UHP-FRC plates with varied steel reinforcement ratios tested under repeated drop-weight impact loads.
It has been found that compressive and tensile strength enhancement predicted using CEB-FIP Model Code
(1990) fits well with test results of the strain rate effect on UHP-FRC material. The numerical results demonstrate the feasibility of the CDP constitutive model for analyzing UHP-FRC under dynamic loading rates. Computed responses are sensitive to CDP parameters related to the tension, fracture energy, and plastic volumetric change. The effect of tensile strain hardening response could be ignored in the nonlinear finite element (FE) analysis of UHP-FRC materials with low strain-hardening behaviour.
The construction industry is expected to go through large transformations since construction automation is anticipated to drastically alter standard processing technologies and could lead to possible disrupting technologies such as 3D concrete printing (3DCP). While 3D printing techniques have been successfully applied in a wide range of industries such as aerospace and automotive, its application in concrete construction industry is still in its infancy. 3DCP can allow freeform construction without the use of expensive formwork, which in return offers excellent advantages compared to conventional approach of casting concrete into a formwork. In the last few years, different 3DCP technologies have been developed. This paper presents the current progress of 3DCP technologies. An innovative methodology recently developed by the authors of this study for formulating geopolymer-based material for the requirements and demands of commercially available powder-based 3D printers is also briefly presented.
The use of 3D printing for rapid tooling and manufacturing has promised to produce components with complex geometries according to computer designs. Due to the intrinsically limited mechanical properties and functionalities of printed pure polymer parts, there is a critical need to develop printable polymer composites with high performance. 3D printing offers many advantages in the fabrication of composites, including high precision, cost effective and customized geometry. This article gives an overview on 3D printing techniques of polymer composite materials and the properties and performance of 3D printed composite parts as well as their potential applications in the fields of biomedical, electronics and aerospace engineering. Common 3D printing techniques such as fused deposition modeling, selective laser sintering, inkjet 3D printing, stereolithography, and 3D plotting are introduced. The formation methodology and the performance of particle-, fiber- and nanomaterial-reinforced polymer composites are emphasized. Finally, important limitations are identified to motivate the future research of 3D printing.
World's First 3D Printed Bridge Opens in Spain
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