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Design and Construction of an Innovative Pavilion Using Topological Optimization and Robotic Fabrication



This research explores innovations in structural design and construction through the generative design technique BESO (Bi-directional Evolutionary Structural Optimization)[1]and the application of robotic fabrication to produce efficient and elegant spatial structures. The innovative pavilion discussed in this paper demonstrates a design and fabrication process and thecollaborationbetween architecture and engineering research groups through a series of small-scale test models and a full-scale model of topologically optimized spatial structures. The focus of this work is the use of a modified BESO technique to optimize the structure which features branches of various sizes, inspired by Gaudi’s Sagrada Familia Bacilica, and the introduction of large-scalerobotic 3D printing developed at RMIT University.The advantages of the new design and construction process are efficient material usage and elegant structural forms.
Design and Construction of an Innovative Pavilion Using
Topological Optimization and Robotic Fabrication
Ding Wen BAOa,b, Xin YANa,c, Roland SNOOKSb, Yi Min XIEa,d,*
a,* Centre for Innovative Structures and Materials, School of Engineering, RMIT University,
Melbourne, 3001, Australia
b School of Architecture and Urban Design, RMIT University,
Melbourne, 3001, Australia
c Centre of Architecture Research and Design, University of Chinese Academy of Sciences,
Beijing, 100190, China
d XIE Archi-Structure Design, Shanghai, 200092, China
This research explores innovations in structural design and construction through the generative design
technique BESO (Bi-directional Evolutionary Structural Optimization) [1] and the application of robotic
fabrication to produce efficient and elegant spatial structures. The innovative pavilion discussed in this
paper demonstrates a design and fabrication process and the collaboration between architecture and
engineering research groups through a series of small-scale test models and a full-scale model of
topologically optimized spatial structures. The focus of this work is the use of a modified BESO
technique to optimize the structure which features branches of various sizes, inspired by Gaudi’s
Sagrada Familia Bacilica, and the introduction of large-scale robotic 3D printing developed at RMIT
University. The advantages of the new design and construction process are efficient material usage and
elegant structural forms.
Keywords: topological optimization, multi-agent, robotic fabrication, prefabricated building, pavilion, mass
1. Introduction
Throughout the history of architecture, the expression of building form has been limited by traditional
building method, in which even slightly irregular forms can significantly change the time and cost
needed for construction [2]. However, Since the introduction of computational aided design technology
into the architectural design at the end of the 20th century, the topic of form-finding based on structural
performance has gained new momentum [3]. The development of architectural technology is closely
related to the evolution of structural morphology, from barrel arches and domes in the period of Greece
and Rome to pendentives and flying buttresses in the period of Byzantium and Gothic; from physical
models used by Antonio Gaudi and Frey Otto to the application of topological optimization technology
to architectural designs, architectural morphology and structural optimization have always been
reinforcing each other.
The Bi-directional Evolutionary Structural Optimization (BESO) method [1] is one of the most popular
techniques for topology optimization. With the further enhancement of the BESO technique by Mike
Xie and his team, more and more architects will have opportunities to use a new intelligent method to
work with the computer interactively, to create innovative, efficient and organic architectural forms and
facilitate the realization of mass customization in the construction industry through the introduction of
Article published in
Proceedings of IASS Annual Symposium 2019 (5), 1-8
advanced 3D printing technologies, such as large robotic 3D printing and some hybrid fabrication
strategies developed by Roland Snook and his research team in RMIT Architectural Robotic Lab. The
concept of topological optimization and the inspiration of Gaudi’s Sagrada Familia Basilica will be
reflected through the pavilion form-finding and its optimization. The new approach of generative
architectural design and fabrication will be introduced in this project, which explores the architectural
implications of topological optimization design through robotic 3D fabrication.
2. Morphological conditioned design based BESO method
Using the BESO method, architects and engineers can generate many elegant and organic forms with
high structural performance. However, there are always inevitable constraints besides structure behavior,
such as functional requirements, construction limitations and aesthetic preference. As a result, it is
necessary to add some controlling methods into BESO process to obtain a form which can meet
composite demand. In this work, three main morphological conditioned design methods are introduced.
2.1. Geometrical restriction
In many practical projects, the geometrical restriction method is the most convenient and effective way
for designers to modify BESO results with some functional requirements manually and explicitly. For
functional cavities, like corridors and windows, they should be dug out of the geometries before
generating the calculating meshes and functional solids can be also reserved in BESO process by setting
them as the non-design domain. For example, the original design domain showed in Figure 1(a) without
any modification generates the form in Figure 1(c). However, with setting the functional cavity and non-
design domain into the model before calculation, the final design can be partly manipulated by designers
intently Figure 1(b) [4].
2.2. Properties influence
Another way to indirectly influence the BESO result is to set the material properties and evolutionary
parameters. With the different relative material Young’s modulus, the distribution density of BESO
structures between the two materials can be designed purposefully [5]. For example, Figure 2(a) shows
a façade model with the bottom boundaries fixed in all displacements and pressure acted on the top
boundaries. And the optimized structures vary significantly with the different material properties of the
top boundaries (blue areas in Figure 2).
(a) (b) (c)
Figure1: The geometrical restriction in BESO method
(a) (b) (c)
Figure 2: Façade optimized structure with different relative material properties:
(a)the load conditions; (b) the BESO result with solid material in non-design domain; (c) the BESO result with
soft material in non-design domain
2.3. Prototype inspiration
Gaudi’s understanding of ‘structural optimization’ in natural form and his strategy of physical structural
modeling are very conceptually close to the principle of BESO and BESO’s logic of form finding [6]
(Figure 3). As an evolutionary algorithm BESO can not only generate forms independently, but also
collaborate with other prototyping techniques in optimization process. The well-known Sagrada Familia
in Barcelona is designed based on anti-hanging physical models by Anthony Gaudi. As a result, using a
new topology optimization tool Ameba [7], this work integrates BESO method with Gaudi’s prototyping
strategy to obtain innovative structure/ pavilion (Figure 4)
Figure 3: The similarities between Sagrada Familia Basilica and pavilion’s top and columns by BESO method
Figure 4: The process of Sagrada Familia inspired pavilion design by BESO topological optimization method
3. Large advanced automated robotic arm 3D printing process
3.1. Application of KUKA Robotic Fabrication
The Advanced Manufacturing Precinct at RMIT University hosts a range of 3D printers for metallic and
polymeric materials and in the Architectural Robotics Lab there are several Kuka robots with various
functions (Figure 5)
Figure 5: RMIT Architectural Robotic Lab
These new techniques for 3D printing fireproof polymer developed by Roland Snooks and his team at
RMIT architecture, are now being used to build structures that can meet building code, which is used in
the National Gallery of Victoria (NGV) interior pavilion panels and partition wall of Monash University
SensiLab (Figure 6).
Figure 6: Monash SensiLab and NGV Floe pavilion
It is an innovative technology combination of KUKA 6 axis robot fitted with a plastic extruder that
designed for building scale prefabricated architectural components, compared with the significant
limitations of traditional small-scale plastic 3D printing (Figure.7).
(a) (b)
Figure 7(a): Small Scale Desktop 3D printer (printing area: 200mm x 200mm x 300mm)
Figure 7(b): Large Robotic 3D printer (printing area: 800mm x 1000mm x 1800mm)
3.2. Code development for printing fractal-like geometries
The whole tree branches system of the pavilion columns comprises four main translucent tree branches-
like polymer columns printed by a desktop printer first (Figure 8) then by a large robotic printer.
Figure 8: 3D printing model testing by small scale desktop 3D printer
The updated code of printing path helps robotic to achieve the aim of printing fractal-like geometries
rather than non-stop and one-curve printing path through introduction “start-stop” script into the original
printing C# code (Figures 9 and 10).
Figure 9: The process of robotic large 3D printing, using the updated code for project exhibited in Hong Kong
Figure 10: Grasshopper simulation of robotic printing path
(red ones are extruded path & blue ones are non-extruded path)
3.3. Testing of polymer materials for 3D printing quality
Material behavior in printing process is another issue that is hard to control. In this work, the relationship
between printing parameters and material stiffness is explored with a series of trials of fractal-like
geometries (Figure 11). From table 1, stability of printing will be significantly influenced by printing
speed once it is more than 200 mm/s; the Z height impacts the stability and speed of printing; and bead
size will cause the thickness of extrusion; one of the most influent parameters is extrude temperature, it
significantly effects the transparency of printing result. Thus, the most successful result is with the 60
mm/s, 2.8 mm Z-height, 4.2 bead size and 210 degree extrude temperature.
Figure 11: Printing example with various qualities (from left to right: bad to good printing qualities)
Table 1: Testing results of polymer materials with various parameters
3.4. Printing Constraints
Current technique has some printing limitation by the issue of large overhang angles without any
supporting material (Figure 12).Therefore a new BESO algorithm is currently being developed to
resolve this issue in the near future.
Figure 12: The result of overhang angles issue in digital and printed models: red part in digital model (left) is
over 32-degree overhang angles that fail to print showing in physical models (right)
4. Conclusion
This innovative pavilion is a demonstration of the combination of new design and construction
techniques, explaining the design and construct process of the pavilion through exploration of emerging
technologies in both digital design and advanced manufacturing, which are respectively topology
optimization-based form-finding and large-scale robotic 3D printing.
The testing results from a series of prototypes clearly illustrate that the optimized structures may play a
useful role in architectural form exploration or provide inspirations for it. The Bi-directional
Evolutionary Structural Optimization (BESO) method provides many possibilities in the process of
creating innovative and efficient forms. Each geometrical restriction, different material properties and
algorithmic parameter may result in different forms, meeting various requirements set by the user.
Also, compared with the traditional small-scale fused deposition modeling (FDM) 3D printing, robotic
3D printing has much greater potential to serve the building industry due to its capability of producing
large-scale printed architectural components with high structural performance.
However, major barriers to the implementation of these technologies in the building industry include a
lack of compression and strength test, UV degradation of the printed polymer components as well as the
significant issue of printing overhang angle, even though some of such printed structures have passed
the fire testing and building codes in Australia as well as partially been put into use. In this present study,
some of the advantages and insufficiencies of the new techniques have been examined. Much more
research and improvement are required in the future. Once the aforementioned issues are resolved, these
new technologies could be widely applied to the mass customized design and manufacturing in the
building industry.
The authors would like to thank several colleagues whose support helped fulfill the research project
described in this paper:
Mr. Charlie Boman and Mr. Hesam Mohamed (Snooks Research Lab, RMIT)
Mr. Yulin Xiong (Centre for Innovative Structures and Materials, RMIT)
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... stability of printing will be significantly influenced by printing speed once it is more than 200 mm/s; the Z height impacts the stability and speed of printing, and bead size will cause the thickness of extrusion; one of the most influent parameters is extruded temperature, it significantly affects the transparency of printing result. Thus, the most successful result is with the 60 mm/s, 2.8mm Z-height, 4.2 bead size and 210 degrees extrude temperature [10]. The purging step is important that can clean the nozzle and ensure the fused polymer extruded from nozzle equally and smoothly. ...
... Currently, the main robotic research is primarily focused on large 3D printing of polymers. Roland Snooks and his team have developed a series of innovative 3D printing technologies to build up several pilot project and large-scale prototypes, such as Monash SensiLab (2017) and NGV Floe pavilion (2018)[10]. ...
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Due to the potential to generate forms with high efficiency and elegant geometry, topology optimization is widely used in architectural and structural designs. This paper presents a working flow of form-finding and robotic fabrication based BESO (Bi-directional Evolutionary Structure Optimization) optimization method. In case there are some other functional requirements or condition limitations, some useful modifications are also implemented in the process. With this kind of working flow, it is convenient to foreknow or control the structural optimization direction before the optimization process. Furthermore, some fabrication details of the optimized model will be discussed because there are also many notable technical points between computational optimization and robotic fabrication.
... Therefore, an innovative structural design-fabrication working-flow based Multi-volume constraint BESO method [27] and Chinese traditional mortise and tension joint carpentry are introduced with a pavilion project named X-Form 3.0 in this paper. Compared with its two previous versions (X-Form 1.0 & 2.0) [12,28], X-Form 3.0 consists of timber components connected with mortise and tension joints, which means that the fabrication of this project is subtractive manufacturing rather than additive manufacturing in the past projects. Therefore, this paper proposes a new structural topology optimisation workflow oriented to subtractive manufacturing. ...
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... These methods can be classified into two categories. One category is the structural shape or topology optimization, which takes a certain index, such as strain energy [4,5] and stress uniformity [6], to measure the structural performance and as the optimization objective. The other category is based on the principle of physical model experiments. ...
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Shape and topology optimization techniques are widely used to maximize the performance or minimize the weight of a structure through optimally distributing its material within a prescribed design domain. However, existing optimization techniques usually produce a single optimal solution for a given problem. In practice, it is highly desirable to obtain multiple design options which not only possess high structural performance but have distinctly different shapes and forms. Here we present five simple and effective strategies for achieving such diverse and competitive structural designs. These strategies have been successfully applied in the computational morphogenesis of various structures of practical relevance and importance. The results demonstrate that the developed methodology is capable of providing the designer with structurally efficient and topologically different solutions. The structural performance of alternative designs is only slightly lower than that of the optimal design. This work establishes a general approach to achieving diverse and competitive structural forms, which holds great potential for practical applications in architecture and engineering.
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This paper presents the application of modern topology optimisation technology to bridge design. Topology optimisation aims to determine the best locations and shapes of cavities in the design domain and therefore is capable of effectively dealing with structural design of infrastructure such as bridges. Several methods of topology optimisation have been developed during the past three decades, among which the evolutionary structural optimisation (ESO) method is popular because of its simplicity in software implementation and effectiveness in solving a wide range of engineering problems. The development of ESO and its advanced version bi-directional evolutionary structural optimisation (BESO) has reached a level of maturity nowadays. Applications of this technique have emerged around the world especially in the past decade. In this paper, the implementation of this technique in structural design is presented, with a particular focus on the design of various bridges. The design applications involve the consideration of different constructional requirements such as support types and selections of the elevation/span. Geometric constraints are also taken into account in the design problem, such as the periodic constraint with which a variety of architecturally aesthetic yet structurally efficient designs are produced. This paper aims to present the application of this promising technology to bridge design and to reveal its potential in a wider range of applications.
In this paper, a new algorithm for bi-directional evolutionary structural optimization (BESO) is proposed. In the new BESO method, the adding and removing of material is controlled by a single parameter, i.e. the removal ratio of volume (or weight). The convergence of the iteration is determined by a performance index of the structure. It is found that the new BESO algorithm has many advantages over existing ESO and BESO methods in terms of efficiency and robustness. Several 2D and 3D examples of stiffness optimization problems are presented and discussed.
This paper will report on a generative performative modeling approach that engages architects and structural engineers in close dialog. We focus on knowledge shared between architects and engineers to apply the Finite Element Analysis based structural design technique Evolutionary Structural Optimization [ESO] as a way to understand or corroborate the performance factors that are significant in determining architectural form. ESO is very close conceptually to the dynamical system of matter and forces of growth itself. It has parallels both mathematical and metaphorical with natural evolution and morphogenesis so it has been poignant to apply the approach to a formal architectural case study in which the generative influence of these processes is inherent.
Towards a structural performance-based architectural design in digital age
  • P F Yuan
  • H Chai
  • Y M Xie
P. F. Yuan, H. Chai and Y. M. Xie, "Towards a structural performance-based architectural design in digital age," Architectural Journal, vol. 11, pp. 1-8, 2017.