Conference PaperPDF Available

Digital Design and Fabrication of a 3D Concrete Printed Funicular Spatial Structure


Abstract and Figures

In recent years, additive manufacturing (AM) and 3D concrete printing technologies have been increasingly used in the field of construction engineering. Several 3D concrete printing bridges were built with post-tensioning technology. However, the current post-tensioned 3D concrete printing projects are mostly in a single direction of force. There are fewer cases of concrete printing funicular spatial structures, and most funicular spatial structures are currently manufactured by casting-in-place in formwork. This paper presents a case of manufacturing spatial 3D concrete printed structure using post-tensioned technology with multiple force direction. The design of the non-parallel printing path, the joints between single units, and the post-tensioned steel cable system in the design and research process are discussed. A funicular spatial structure is built, and a method of manufacturing 3DCP funicular spatial structure is proposed.
Content may be subject to copyright.
1,3,6College of Architecture and Urban Planning, Tongji University
2,4,5School of Architecture and Urban Design, RMIT University, 0000-0002-0503-1696, 0000-0002-2027-9227, 0000-0002-2543-2307, 0000-0002-0616-6787, 0000-0003-1395-8747, 0000-0002-2871-377X
Abstract. In recent years, additive manufacturing (AM) and 3D
concrete printing technologies have been increasingly used in the field
of construction engineering. Several 3D concrete printing bridges were
built with post-tensioning technology. However, the current post-
tensioned 3D concrete printing projects are mostly in a single direction
of force. There are fewer cases of concrete printing funicular spatial
structures, and most funicular spatial structures are currently
manufactured by casting-in-place in formwork. This paper presents a
case of manufacturing spatial 3D concrete printed structure using post-
tensioned technology with multiple force direction. The design of the
non-parallel printing path, the joints between single units, and the post-
tensioned steel cable system in the design and research process are
discussed. A funicular spatial structure is built, and a method of
manufacturing 3DCP funicular spatial structure is proposed.
Keywords. 3D concrete printing; Robotic fabrication; Prestressed
concrete; Funicular spatial structure; Structural optimization; SDG 9;
SDG 11; SDG 13.
1. Introduction
In the last decade, 3D concrete printing has demonstrated its potential to change the
traditional construction way by printing concrete walls without conventional
formworks (Le et al., 2012), which creates new possibilities in both architectural design
and environmental protection. The application strategies for 3D concrete printing in
building construction can be generally divided into on-site printing (Scott, 2020)
(Mechtcherine, 2019) and prefabricated assembly. For prefabricated assembly 3DCP
project, post-tensioned technology is widely applied to make separated printed units
become a whole. The past five years have seen the completion of several post-
tensioned 3D concrete printing bridge projects (Vantyghem et al., 2020) (Salet et al.,
POST-CARBON, Proceedings of the 27th International Conference of the Association for Computer-
Aided Architectural Design Research in Asia (CAADRIA) 2022 , Volume 2, 71-80. © 2022 and published
by the Association for Computer-Aided Architectural Design Research in Asia (CAADRIA), Hong Kong.
2018) (Zhan et al., 2021). However, these projects are tensioned in a single direction,
which is why all are beam-like structures, namely bridges.
Typically, elements printed in concrete are achieved by extruding wet paste-
material in layers which eventually build up the desired shape, which is first described
as Contour Crafting in 2004 (Khoshnevis et al., 2004) and has been popular still now.
However, the CC technology is limited to vertical extrusion, hence yielding 2.5D
topologies (vertical extension of a planar shape) (Gosselin et al., 2016). Concrete units
printed in this way are best stressed in the vertical direction, which is why many 3D
printed structures are tensioned in one direction.
From the research of Gosselin, the method of non-parallel printing is described,
which makes it possible to realize multi-angle printing (Gosselin et al., 2016). The
arched masonry structure from BRG et al. (2021) fully demonstrates the advantages of
this printing method in building funicular spatial structure. Separated units are printed
in layers orthogonal to the main structural forces and they compress each other to form
a compression-only funicular structure. In this arched masonry structure, there are no
joints connecting the separate units, yet joint design is important in post-tensioned
spatial structures.
The research project described in this paper is committed to exploring how to
achieve post-tensioned 3DCP funicular spatial structure. Macroscopically, post-
tensioning technology has been applied to achieve the efficiency and rationality of the
structure. At the micro-level, non-parallel printing technology is applied to realize the
printing of all separated units. A set of steel plate system for positioning and a set of
post-tensioned pre-stressed steel bar system were applied. Finally, an experimental
funicular spatial structure with a range of about 6m*6m*3m was built. The project
discussed the rationality of the structural design of large-scale concrete printing
funicular spatial structure and how to use these techniques to achieve the complexity
of the printing structure.
2. Research and Prototyping
In order to verify the feasibility of prestressed 3D concrete printed spatial structure and
to discover potential problems during installation, a simple small-scale experimental
prototype was designed, and the printing and installation tests were carried out.
Figure 1. The development of the prototyping design
This simple funicular spatial structure is designed using PolyFrame (Masoud et al.
2019), a Grasshopper plugin based on 3D graphic statics. This plug-in is good at
constructing purely compressed space structures. While in this prototype, prestressed
steel bars can be used to simulate this compressed state. It is designed into a uniform
structure composed of four identical units and four curved steel bars. The four concrete
members are compressed tightly together to form a stable structure that presses and
restrains each other. Figure 1 shows the development of the prototyping design.
The segmented units are geometries with multiple direction, which means that they are
non-developable curved surface. In Lim et al.’s (2020) work, a method of printing a
non-developable curved surface is described (Lim et al., 2020). Compared to traditional
method, it required temporary fabric formwork supported by height-adjustable rods.
Lim has proposed in his theory within this technology, which is to print with saddle
and dome surface on the temporary fabric formwork. The limitation of this kind of
method is that a specific height-adjustable system is required, and each piece of printing
will consume one piece of fabric. In addition, the temporary fabric formwork has
relatively low accuracy and hard to control, which will increase the printing error and
may eventually lead to the failure of the entire structure when assembly.
In prototype design, a method of printing the base with concrete material is
proposed. As shown in Figure 2, a triangular base was designed according to the shape
of the printed segment in this experiment. This base has three inclined surfaces that
need to be printed with a specific printing path. After base printing, a piece of plastic
flim was in use to separate the unit from the base that it attaches to. With this technique,
four identical structural segments are printed.
Figure 2. Left: printing process, Mid: toolpath, Right: steel bar system
Although the printed base can ensure that the inclinations of the three slope surfaces of
each unit are accurate. However, from a micro perspective, as it's shown in Figure 3,
the inclined surface of the printed base is stepped. The bottom of the final printed object
cannot fit this inclined curved surface completely, which makes the connecting surface
of the prints uneven.
Figure 3 shows that because the nozzle has an unchangeable size, the printing
height of the first layer needs to be raised to prevent the print head from rubbing against
the inclined surface of the base. Therefore, the first layer of the printed component is
obviously wider, and the layer height is also different from others.
Figure 3. A micro view of the filament
Due to the superposition of the previous two reasons, the stability and accuracy of
the entire prototype structure were declined from expectation. When the printed
components were assembled, the connecting surface could not be fully attached. This
leads to insufficient assembly accuracy of the printed parts and affects structural
stability. Figure 4 describes the printing process and the assembly process.
Figure 4. Record of printing and assembly process
3. Computation design
The design result is attributed to the collaboration of two software, Polyframe, which
generates a purely compressed frame, and Ameba (Xie et al. 2016), which calculates
the volume through topological optimisation. With the help of PolyFrame, a system of
purely compressed funicular spatial structure is created upon the basis of 3D graphical
statics. Then optimization based on Ameba was introduced into the design. Some
members were set as non-designed regions under the same boundary conditions, and
then the Ameba algorithm was used, followed by 90 iterations. Figure 5 shows the
development of the design process. As a result, an efficient spatial structural system
based on mesh optimization was obtained, which predicts the basic material
distribution of the final pavilion shape and improves the feasibility of concrete 3D
Figure 5. Iterations in Ameba
The final structure design needs to be divided into small pieces for printing. The
direction of the force, the maximum printing height, and the maximum printable
inclination are 3 main factors that need to be considered during the segmentation
process. Finally, the whole structure is divided into 18 segments, each of which is less
than 1500mm in height. To meet the requirements of reliable printing, every segment
has at least one horizontal surface, with a maximum inclination angle no more than 45
degrees. Each column and beam are divided into two and three segments respectively.
The remaining three outward heads each become an independent piece. Each segment
is attached with one or two steel plates, which are used for positioning in assembly
process. The division of the segments, the position and the serial number of steel plates
are shown in Figure 6.
Figure 6. Segmentation
To simulate the calculation results of PolyFrame, 9 steel bars were added to this
system. Three of them are connected to the column foundation from the overhanging
ends and each beam has two steel bars. All steel bars are pre-stressed by post-
Figure 7. Nine steel bars
This funicular structure is post-tensioned in multiple force direction, which create
another difficulty in accurate positioning. The joints between single units need to be
specially designed. 3D printing concrete ink usually has good fluidity during
movement and satisfying standing behavior at static state (Zhang et al. 2018). The
printing filament is in a wet-state and maintains a certain degree of plasticity for a
certain period of time after extrusion. Exploit this property of 3DCP filaments, some
scholars have demonstrated the feasibility of implanting micro cable during filaments
deposition process (Ma et al. 2019) (Li et al. 2020). In this study, a method of
implanting steel plates as positioning joints between the units during the printing
process was employed.
Each segment has at least one steel plate, the segment in the middle of the beam has
two steel plates. The printing of a single unit is paused during the printing process and
the steel plates are then manually placed. After inserting steel plate, the printing process
is continued. The concrete and the steel plates will become a whole when concrete gain
The thickness of the steel plate processed by CNC milling machine is 4mm. There
are two kinds of holes with diameters of 20mm and 50mm on the steel plate. 20mm
holes are used for steel pipe welding during assembly. It plays the role of positioning
between segments. The 50mm hole is where the steel bar passes through. The edge of
the steel plate is designed to be zigzag, as shown in Figure 8, so that the steel plate and
the concrete printing filament can be combined more firmly. The jagged edges make
the filaments on both sides have a larger contact area. This is because, through the early
printing experiments, it was found that the steel plate with a smooth edge will cause
poor connection of the filaments separated by the steel plate. The printing segment
brokes easily at where the smooth steel plate was placed.
Figure 8. Steel plates with zigzag edges
4. Robotic fabrication
The final structure is a multi-directional pre-stressed structure. The segmented unit is a
multi-directional block, which cannot be printed by the traditional horizontal printing
path. As shown in Figure 9, three sets of non-parallel planes are used to cut the printed
units and then the intersected curves are connected to form the final path. Filaments are
printed in non-uniform and non-parallel layers. The printing layers are orthogonal to
the prestressed tensile direction so that the printing filaments within the structural unit
can be tightly compressed together.
Figure 9. Toolpath generation
In the prototype experiment, the bottom of the printing segments was uneven which
will cause poor integrity when assembly. The accuracy of the connecting faces is not
only an important factor but also an essential guarantee for the structure stability.
To achieve good connectivity, the contact surface of each unit must be flat. Thus,
the printing strategy with the multi-directional side down in the experiment is
abandoned. Every unit is printed with one-direction side down to obtain a rational flat
surface connected with the base. This contact surface allows the unit to be stressed
evenly during the printing process to ensure stability of the final structure.
The printing process is described in Figure 10:
Place the tray (for the convenience of subsequent transportation)
Lay the plastic film
Print the base and pause for a horizontal surface)
Lay the plastic film (for the subsequent separation of the base and the unit)
Print the first 4 layers of the unit and pause
Manually place the steel plate
Print the remaining part
Manually place the 2nd steel plate (for units in the middle of the beam)
Print the remaining part (for units in the middle of the beam)
Figure 10. Printing process
After all the printing work is completed, each unit has been cured for at least 14 days
to ensure that it has obtained sufficient early yield strength. The installation process is
as follows:
What installed first is three pillars. The steel bars inside the three pillars are welded
to the foundation. Inside the three pillar legs, 300mm-thick mortar is poured to
connect the pillars with the embedded steel components.
Install the second section of the column.
The three beams are assembled on the ground respectively, and then the three beams
are hoisted up.
The three overhanging units are put on last.
The connections between the units are installed with anti-collision strips with a
width of 30mm. The steel pipes are welded to the steel plate in the 20mm hole, and
then assembled with the other segment whose steel plate they go through to achieve
Figure 11. Record of the assembly process and final outcome
precise positioning between the units. Pre-stressed steel bars with a diameter of 15mm
pass through the 50mm hole in the steel plate and reach three overhang ends
respectively. At the end of each overhang end, 9 steel bars are tightened with nuts to
realize the post-tension of the entire structure.
5. Result and discussion
The final structure presents a relatively good surface quality. Although there are some
discordant seams in some connections, but the overall quality is within the acceptable
range of the architectural scale. The reasons for this may be:
The error of non-parallel 3D printing is larger than that of traditional 3D printing.
The deviation of the position of the pillars.
The method of placing the steel plate during the printing process needs to be
optimized. It is found that the filament where holds the steel plate will sightly bulge,
which declare that the method of embedding the steel plate in the concrete need further
investigation. Methods such as optimizing the zigzag design, reducing the size or
thickness of the steel plate deserve further exploration.
At present, the mainstream concrete 3d printing construction is divided into two
categories: on-site printing and prefabricated assembly. The on-site printing
technology is relatively mature and there is no segmentation problem. When it comes
to prefabricated assembly, however, there are more issues to be settled.
In general, the concrete printing segments are relatively heavy and fragile, which
leads to lots of difficulties in assembly period. In this project and the arched masonry
structure from BRG et al. (2021), although each unit was manufactured using template-
free 3D printing technology, a large amount of supports were used for positioning,
including wood scaffold, during the assembly process, which led to a significant
increase in both construction and environmental costs. Recent years, non-parallel
concrete printing becomes popular and further eliminates the limitations of complex
shapes. It is foreseeable that more large-scale 3DCP funicular spatial structures will
emerge in the near future, which will also mean more complex scaffolds are needed.
In this context, perhaps 3DCP technology needs to be re-evaluated, because the best
option for these complex scaffolds is wooden waffle scaffold.
This spatial structure is part of the result of RMIT master studio "Intelligent Force
Printing", studio leaders and all students of the studio have made great contributions to
this project.
Studio leaders: Philip F. YUAN (RMIT Visiting Professor), Dingwen ‘Nic’ Bao
(RMIT lecturer)
Teaching Assistants: Hao Wu, Xinjie Zhou, Xiang Wang
Students: Bowen Li, Da Wang, Guowei Xia, Jingyi Liu, Ruoxing Wang, Wenjie
Gai, Xinyu Wu, Yuhan Bao, Zengwei Wang, Zhangxizhi Wang, Zhengqian Peng,
Zhuohua Tan, Ziyan Li, Ziyu Zhou (Sorted by initial letter)
This research was supported by National Key R&D Program of China (Grant
No.2018YFB1306903), National Natural Science Foundation of China (Grant No.
U1913603), and Shanghai Science and Technology Committee (Grant No.
Block Research Group (BRG), Zaha Hadid Architects Computation and Design Group
(ZHACODE), Incremental3D (in3D), Striatus - 3D concrete printed masonry bridge,
Venice, Italy, 2021. from
Gosselin, C., Duballet, R., Roux, P., Gaudillière, N., Dirrenberger, J., & Morel, P. (2016).
Large-scale 3D printing of ultra-high performance concretea new processing route for
architects and builders. Materials & Design, 100, 102-109.
Khoshnevis, B. (2004). Automated construction by contour craftingrelated robotics and
information technologies. Automation in construction, 13(1), 5-19.
Le, T. T., Austin, S. A., Lim, S., Buswell, R. A., Gibb, A. G., & Thorpe, T. (2012). Mix
design and fresh properties for high-performance printing concrete. Materials and
structures, 45(8), 1221-1232.
Li, Z., Wang, L., Ma, G., Sanjayan, J., & Feng, D. (2020). Strength and ductility enhancement
of 3D printing structure reinforced by embedding continuous micro-cables. Construction
and Building Materials, 264, 120196.
Lim, J. H., Weng, Y., & Pham, Q. C. (2020). 3D printing of curved concrete surfaces using
Adaptable Membrane Formwork. Construction and Building Materials, 232, 117075.
Ma, G., Li, Z., Wang, L., & Bai, G. (2019). Micro-cable reinforced geopolymer composite for
extrusion-based 3D printing. Materials Letters, 235, 144-147.
Masoud Akbarzadeh. Andrei Nejur.(2019). Polyframe. From
Mechtcherine, V., Nerella, V. N., Will, F., Näther, M., Otto, J., & Krause, M. (2019). Large-
scale digital concrete constructionCONPrint3D concept for on-site, monolithic 3D-
printing. Automation in Construction, 107, 102933.
Salet, T. A., Ahmed, Z. Y., Bos, F. P., & Laagland, H. L. (2018). Design of a 3D printed
concrete bridge by testing. Virtual and Physical Prototyping, 13(3), 222-236.
Scott, C. (2020, March 17). Chinese construction company 3D prints an entire two-story
house on-site in 45 days. from
Vantyghem, G., De Corte, W., Shakour, E., & Amir, O. (2020). 3D printing of a post-
tensioned concrete girder designed by topology optimization. Automation in
Construction, 112, 103084.
Xie, Y. M. (2016). Ameba. From
Zhan, Q., Zhou, X., & Yuan, P. F. (2021). Digital Design and Fabrication of a 3D Concrete
Printed Prestressed Bridge.
Zhang, Y., Zhang, Y., Liu, G., Yang, Y., Wu, M., & Pang, B. (2018). Fresh properties of a
novel 3D printing concrete ink. Construction and building materials, 174, 263-
... This is an optimization process for both design and construction, in which digital modelling methods and digital fabrication techniques are involved. Recently, several projects with structural performance-based 3D concrete printing have been constructed, proving that this shift is taking place and valued by designers (Bhooshan et al., 2022;Wu et al., 2022). These emerging practices signal a shift in 3DCP from an emphasis on formwork-free, rapid construction to an emphasis on less material usage and sustainability. ...
This paper presents the design and fabrication of an efficient steel–concrete composite beam prototype using structural optimization methods and innovative 3D concrete printing (3DCP). In traditional building industry, concrete objects like slabs or beams are cast by using low-cost standardized formwork, resulting in their high material usage and large carbon footprints. Although the development of large-scale 3DCP offers a formwork-free and rapid construction method, the elements created are like those created by standardized formwork. To achieve formwork-free construction of efficient concrete structures, this paper proposes the method of structural performance-based 3DCP. The work in this paper uses multi-material BESO technique and non-horizontal 3D printing to fabricate an efficient steel–concrete composite beam prototype with a span of 4 m. According to rough calculations, the optimized structure saves approximately 60% of concrete and 50% of steel compared to a conventional concrete beam. Combined with previous studies, this paper summarizes and proposes an important shift that is taking place in 3DCP. The general workflow of Structural Performance-Based 3D Concrete Printing is summarized, and future research topics are discussed. The study in this paper demonstrates the valuable outlook of the combination of structural performance-based design and precise material deposition methods, which could contribute to the UN Sustainable Development Goals.
... Compared to desktop 3D printing, LFAM for architecture and landscape projects needs to consider topography conditions and construction costs, which cannot be realized by simply increasing the number and volume of printers (Duty et al., 2017;Krishnamurthy et al., 2022). A more practical approach is to divide the structure into multiple components that fit the printing range of the printer, and then print and transport these components to the construction site for installation (Grasser et al., 2020;Wu et al., 2022a). A criterial research question of architectural scale LFAM is how to divide and convert the structure into transportable, printable, and easy-to-assemble components. ...
Full-text available
3D concrete printing (3DCP) technology is a construction method that offers a unique combination of automation and customization. However, when the printing area goes large, generating the print path becomes a sophisticated work. That’s because the customized print path should not only be expandable but also printable, such rules are hard to follow as both the printing area and construction requirements increase. In this paper, the Shenzhen Baoan 3D Printing Park project serves as a case study to introduce space-filling and print path generation methods for three types of large-area concrete pavement. The space-filling methods utilize geometry-based rules to generate complex and expandable paving patterns, while the print path generation methods utilize construction-oriented rules to convert these patterns into print paths. The research provides easy-to-operate design and programming workflows to achieve a pavement printing area of 836 sqm, which significantly increases the construction scale of large-format additive manufacturing (LFAM) and shows the potential of 3D printing technology to reach non-standard results by using standard workflows.
... Zhao et al., 2016). Studies and practices have shown that large scale additive manufacturing such as D-shape (Cesaretti et al., 2014) Contour Crafting (Khoshnevis et al., 2006) and 3D concrete printing (3DCP) (Wu et al., 2022) have demonstrated the potential of using 3D printing technology to produce building components. ...
Full-text available
The construction industry faces severe problems resulting from low productivity and increasing shortages of skilled labor. The purposeful digitalization and automation of all relevant stages, from design and planning to the actual construction process appears to be the only feasible solution to master these urgent challenges. Additive concrete construction has a high potential to be a key part of the solution. In the first place, technologies are of interest which would enable large-scale, on-site manufacturing of concrete structures in accordance with the demands of contemporary architectural and structural design. The article at hand evaluates the state-of-the-art with respect to these requirements and presents the CONPrint3D concept for on-site, monolithic 3D-printing as developed at the TU Dresden. This concept is driven by the demands and boundary conditions of construction practice. It complies with common architectural norms, valid design codes, existing concrete classes and typical economic constraints. Furthermore, it targets the use of existing construction machinery to the highest possible extent. The interdisciplinary team of authors illuminates various perspectives on the new technology: those of mechanical engineering, concrete technology, data management, and construction management. Some representative results of completed work in these fields are presented as well.
Full-text available
The current state of research and development into the additive manufacturing of concrete is poised to become a disruptive technology in the construction industry. Although many academic and industrial institutions have successfully realised full-scale structures, the limitations in the current codes of practice to evaluate their structural integrity have resulted in most of these structures still not being certified as safe for public utilisation and thus deemed as test prototypes for display purpose only. To realise a 3D concrete printed (3DCP) structure which could be certified safe for public use, a bridge was realised using the print facility of the Eindhoven University of Technology (TU/e) based on the concept of ‘Design by Testing’. This paper holistically discusses the complications encountered while realising a reinforced 3DCP bridge in a public traffic network and decisions taken to find solutions for overcoming them.
Full-text available
This paper presents the experimental results concerning the mix design and fresh properties of a high-performance fibre-reinforced fine-aggregate concrete for printing concrete. This concrete has been designed to be extruded through a nozzle to build layer-by-layer structural components. The printing process is a novel digitally controlled additive manufacturing method which can build architectural and structural components without formwork, unlike conventional concrete construction methods. The most critical fresh properties are shown to be extrudability and buildability, which have mutual relationships with workability and open time. These properties are significantly influenced by the mix proportions and the presence of superplasticiser, retarder, accelerator and polypropylene fibres. An optimum mix is identified and validated by the full-scale manufacture of a bench component. KeywordsAdditive manufacturing–Build–Concrete–Extrusion–Open time–Printing
In this paper, we study the printing of non-developable curved panels using existing 3D concrete printing technology combined with a novel Adaptable Membrane Formwork. The Adaptable Membrane Formwork consists of a grid of threaded rods, whose heights are adjustable and covered by a membrane sheet. Using this method, we were able to 3D-print, for the first time, Saddle and Dome-shaped concrete surfaces, which are non-developable. The printed specimens had good print quality and geometric fidelity, as shown by quantitative assessment. The proposed method thus demonstrates great potential for the 3D printing of freeform, curved and architectural facades.
3D concrete printing (3DCP) is used to manufacture freeform components by digitally controlling the distribution of concrete materials without requiring additional formwork. Recurring issues associated with 3DCP are low tensile strength and poor ductility of the nonreinforced structures. In this paper, a reconciliation printing methodology is presented for manufacturing reinforced geopolymer structures by simultaneously embedding micro-cables during the printing process. Structural arched beam and spiderweb-like structures were 3D printed and used to verify the feasibility of the proposed reinforcing method by evaluating their shape-based structural performance. A self-developed loading device was used to simulate the natural tension-only stress condition of a real spiderweb. The loading capacity of the cable-reinforced web structure was calculated and compared to the test results, which verified the bonding and the reconciliation between the micro-cable and the geopolymer matrix. As compared to the nonreinforced structures, the failure mode of the reinforced structures changed from brittle to ductile with multiple cracks, and the micro-cable reinforcement altered the strain evolution patterns. This study demonstrates that the strength of the reinforced structure was substantially increased. Further, both the method of reinforcement and the specific configuration of the 3D printed structures play a crucial role in resisting deformation and damage.
In this paper, the digital design and manufacturing of a post-tensioned concrete girder is presented. We bring together two emerging technologies that show great potential for realizing highly-efficient concrete structures: topology optimization for simulation-driven design and 3D concrete printing (3DCP) for manufacturing of optimized shapes. While this is not the first-ever 3D-printed concrete structure, it is the first demonstration of how topological design in combination with 3D concrete extrusion printing allows for creating efficient structures with reduced use of materials. As the implementation of a specific optimization procedure for post-tensioned concrete structures is so far available in 2D only, some design post-processing was necessary, and a 3D finite element analysis was performed. After realization of the 3DCP element (i.e. printing and assembly), the girder's structural performance was experimentally verified using digital image correlation. The deflection of the girder was compared with the numerical results. The manuscript includes thorough discussions on the manufacturing challenges-including printing setup, assembly and integration of reinforcement.
Geopolymer has been applied to accommodate the rapid development of 3D printing in civil engineering practices and contributed this technique to reach its maximum eco-friendly potentials by eliminating the use of Portland cement. However, inherent problems with 3D printing concrete lie in the low tensile strength and poor ductility due to non-reinforcement, which greatly limit the application of 3D printing materials and structures. Hence, this study experimentally explores the feasibility of directly entraining a continuous micro steel cable (1.2 mm) during filaments (12 mm) deposition process, forming a reinforced geopolymer composite material. Three different printing path configurations are deigned to verify the applicability of micro-cable reinforced geopolymer composite for extrusion-based 3D printing. Flexural bending capacities of the proposed composite is measured and evaluated through four-point bending test. The results prove the well bonding and coordination of the micro-cable and geopolymer. Significant improvement of mechanical strength, toughness and post-cracking deformation of geopolymer composite are demonstrated.
Although automation has advanced in manufacturing, the growth of automation in construction has been slow. Conventional methods of manufacturing automation do not lend themselves to construction of large structures with internal features. This may explain the slow rate of growth in construction automation. Contour crafting (CC) is a recent layered fabrication technology that has a great potential in automated construction of whole structures as well as subcomponents. Using this process, a single house or a colony of houses, each with possibly a different design, may be automatically constructed in a single run, imbedded in each house all the conduits for electrical, plumbing and air-conditioning. Our research also addresses the application of CC in building habitats on other planets. CC will most probably be one of the very few feasible approaches for building structures on other planets, such as Moon and Mars, which are being targeted for human colonization before the end of the new century.