| Sustainability and Construction Scale Additive Fabrication: Opportunities for Architecture and the Construction Industry
Additive Fabrication also known as Rapid Manufacturing is emerging as an important new field that is revolutionizing the way goods are manufactured, with a broad range of materials including high strength plastics and titanium and products available online including toys, jewelery and furniture to parts in jet fighters. These developments are now being adapted to the construction industry, with the first projects commissioned in Italy using the D_Shape technique.
Construction sustainability is increasing in importance and urgency as the developing world strives toward Western living standards and the world is faced with human induced global warming. The construction industry consumes much of the world's resources and produces approximately a third of the world’s waste. The current rate of construction in China provides an alarming example; China will build and replace in just 15 years from 2000, more than half of its urban residential and commercial building stock (Zhu and Lin, 2004). Government sponsored agencies are increasingly calling for the construction industry to modernize to meet the challenges presented by the environment and resource depletion. The industry is struggling to meet this challenge through industrialization and adoption of processes from industries such as aerospace and automotive industries.
This article evaluates the application of current and emergent technologies combined with construction scale additive fabrication, to assess how these technologies could be employed to assist the construction industry tackle issues of construction sustainability in buildings.
The term construction sustainability has not been clearly defined to date and terms such as; sustainability, green and ecological are often used interchangeably, despite the terms having quite different meanings. The Brundlandt report broadly defined sustainability more than two decades ago; ‘Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs’ (United Nations, 1987,Ch. 2.1). This definition however is too broad for the purposes of this article, therefore ‘construction sustainability’ is used and includes the following:
Material use – raw and processed material inputs throughout the life of the building, sustainability of the resource, waste, recyclability.
Energy use – embodied energy of raw and processed materials, sustainability of the resource, fabrication of the building, operation of the building, decommissioning, capture of energy from the environment.
Air – pollution, recycling
Water – use, collection, waste and recycling
Bio-diversity – support and improvement of flora and fauna
Human factors – functional, thermal, acoustic, daylight access, ventilation.
It is important to add that the assessment of a design and its built product need to be assessed broadly as a system within the much larger eco-system of its surrounding environment. This is at present very difficult to achieve and assessment is largely broken down into incremental calculations of separate systems to comply with regulations.
Construction Scale Additive Fabrication
Additive fabrication techniques derive from the field of rapid prototyping, developed in Japan and the USA during the late 1980’s and 90's. Additive fabrication is defined as a process, which builds up three dimensional objects by the automated curing and/or deposition of successive layers of material.
The additive fabrication industry (also referred to as rapid prototyping and rapid manufacturing) is fast maturing. An excellent signal for this is that rapid prototyping devices can now be desktop-sized1 and available at a price point that enfranchises even students. Current rapid prototyping technology is now being scaled-up for the manufacture of full-size components and systems and can be defined to neatly fit into three categories.
- Synthetic stone
A number of construction scale additive fabrication techniques have been developed since the mid 1990’s. These techniques include a system by Dr. Khoshnevis in 1996 called contour crafting, Pegna in 1997 based on Navajo sand painting, Robocrane by Williams in 2004, D-Shape 2006 and Freeform Construction developed at Loughborough University. The techniques developed by Pegna and Williams have not been actively pursued, while the Contour crafting, D-Shape and the Freeform Construction machines are all actively undergoing development, producing walls of various sizes and large sculptural objects. Each of the fabrication techniques use subtly different fabrication methods, processes and materials but can all be defined as producing synthetic stone. Below is a brief summary of two of the techniques actively being developed.
Contour crafting developed at the University of Southern California, by Dr. Khoshnevis is a deposition machine that uses concrete with added chemicals to control the viscosity and curing time of the material. The extrusion head places material with a robotically controlled top and side trowel, which controls the profile of the deposited material allowing a smooth surface finish on the exposed side of the build. The contour crafting machine deposits two layers of material parallel to each other, leaving a cavity, which is filled with bulk material as the build progresses; this should allow relatively fast fabrication of a sacrificial formwork, that becomes part of the finished structure. www.contourcrafting.org/
The D_Shape technique has demonstrated true freeform construction with the fabrication of a two meter tall prototype (Figure 1) of the full size ‘Radiolaria’ presently under construction and due for installation on a roundabout in Pontedera, Italy by June 2010. The fabrication process begins with depositing a layer of sand 5-10mm deep over the entire build area. A gantry controlled deposition head then moves across the surface and selectively prints an inorganic binder onto the sand. This process is repeated with subsequent layers of sand and deposition of the binder until the build is complete (Figure 2). http://www.d-shape.com/
Figure 1 (left) – D_Shape scaled ‘Radialaria’ 2008
Figure 2 (right) – Printing of the ‘Parametric column 1’ 2009
There are interesting benefits inherent in the D_Shape process; the base materials and the resulting synthesized stone have good credentials as a sustainable construction process, the materials used are all naturally occurring substances, which require little processing before use in the fabrication process. The material produced is stone, although created in a fraction of the time that nature takes to create it naturally. This results in a process that produces very little carbon, unlike concrete and cement, which are a major source of CO2 emissions. D_Shape also reprocesses almost all of its waste for reuse in the fabrication process.
Construction scale additive fabrication has an intrinsic advantage of producing very little waste compared to ‘subtractive’ (milling stone to the desired shape) and ‘formative’ processes (use of formwork with concrete) and even other ‘additive’ building processes (brick laying). During the entire visit to the D_Shape plant over nine weeks from July 2009, very little waste was produced, due to the efficiency of the process and the reuse of almost all waste materials throughout the process, from production of the catalyst to post processing of 'printed parts.'
Virtual Prototyping, Analysis and Optimization
Parallel Industries, especially aerospace and automotive industries, have significantly embraced the use of parametric design, virtual prototyping and analysis. Many of the companies interviewed in my research in 2008 are now reaching the stage where the 3D model is the primary data resource. This trend is also emerging within leading architecture and engineering practices, with increasing reliance on 3D computational design, as well as the use of optimization tools as part of the design process. Arup consulting engineers have been developing and implementing an array of computational tools to deal with the escalating complexity within their projects. Projects such as the ‘Water Cube’ for the 2008 Beijing Olympics benefited through the use of optimization of the highly complex tubular structural steel frame canopy based on soap bubble formations. Running thousands of iterations of analysis and optimization to minimize weight and ensure structural integrity.
Figure 3 - Cox & Arup rectangular stadium (image courtesy of Arup).
A further development of the optimization process developed for the Water Cube project was made on the Rectangular Pitch Stadium in Melbourne, Australia (Figure 3). Where the optimization process identified 10 percent savings of tonnage in the roof steelwork members and an optimum roof profile. The outcome was increased material efficiency and reduced demand on natural resources. Emerging optimization techniques have an even greater potential within the construction industry especially used in concert with emerging construction techniques.
Topology optimization has been developed by a number of universities around the world, such as the Department of Mechanical Engineering, Technical University of Denmark and the Innovative Structures Group, RMIT University Melbourne. Bi-directional structural optimization (BESO) developed at RMIT University can be used to optimize structures with a variety of loads and constraints within a design domain. This model can include ‘non-design elements’ which will not be modified in the optimization process, such as floors in a building. The BESO software runs parallel to the Abaqus finite element analysis software (FEA). Analyses of material stress is made at each iteration prior to BESO adding or subtracting material.
Figure 4 – BESO optimization tests on a cantilevered 3 story building - James Gardiner, SIAL RMIT 2009
Topology optimization is well suited to be paired with construction scale additive fabrication techniques, as the non-Euclidean geometry generated is difficult to build using conventional building methods (Figure 4). The primary cost constraints for additive fabrication are build time and material usage, regardless of geometrical complexity, which is often an issue with using optimized structures produced by topological optimization techniques.
Topology optimization offers significant opportunities in the future for the development of designs which are highly calibrated to calculated loads, at the building scale and also at an elemental scale such as internal structures of columns or walls. For example Figure 4 (left) above illustrates a fairly conventional multi-story building, which has been optimized through the experimental RMIT university BESO software. Figure 4 (mid) illustrates an early stage within the optimization and Figure 4 (right) illustrates the optimized structure. The program is at present primarily useful for determining optimal topologies, rather than determining the ideal topology and material required based on optimal material loadings, a much more complex issue2 and one which would be extremely useful for architects and engineers.
The projects discussed above indicate how broadly such optimization techniques can be applied, with multiple parameters being assessed and outcomes that enable highly complex problems to be explored with tangible construction sustainability outcomes. There are however still very real constraints that are imposed by software efficiency and computer processing power that are making the optimization in concert, of the multiple issues that architects and engineers must negotiate, difficult to achieve at present.
Construction Scale Additive Fabrication
Construction scale additive fabrication technologies are well suited to take advantage of virtual prototyping, analysis and optimization technologies for construction sustainability, due to their complete dependence on CAD data for fabrication. As construction scale additive fabrication and associated material technologies mature, there will be considerable opportunity to integrate both passive and active systems into buildings, incorporating construction sustainability in both the fabrication and operation of the buildings.
Figure 5 - (Left) Modular optimized assembly. James Gardiner, 2006 SIAL RMIT
The cut away section perspective above (Figure 5) illustrates the potential of Construction Scale Additive Fabrication techniques in the buildings; the walls are no more expensive if they are freeform rather than rectilinear, allowing increased expression on the building façade and interior, while also responding to breezes and light. Wall thickness does not need to be constant and the internal structure of the wall can be hollowed out to use less material, while responding to thermal requirements and to structural loads with the incorporation of internal structure. Joints between building elements can be fabricated directly, incorporating waterproofing caskets and connecting dowels. Acoustic treatments and textures could be applied to the internal and external surfaces of the building, improving noise pollution and audibility. Allowance for fixings for elements such as windows, raised floors and services. Some of these aspects have been demonstrated with the fabrication of a column with D_Shape.
Figure 6 - (left) ‘Parametric column 1’ designed by James Gardiner, faan studio.
Figure 7 - (right) ‘Parametric column 1’ printed in sections (fabricated by D_Shape 2009).
The parametric column 1 (above Figure 6 & Figure 7) is the first test demonstrating methodologies to be implemented in the ‘Villa Rocce’ house commissioned for construction in 2010 in Sardinia Italy. The 3.2 meter column demonstrates the integration of internal geometry for reduction of materials, while increasing structural strength based on distribution of loads. The column also integrates internal ‘conduits’ for the integration of reinforcement within the column at time of assembly.
Current virtual prototyping, analysis and optimization techniques are well suited for use on projects using additive fabrication, due to the ability of these additive fabrication techniques to fabricate complex non-Euclidean structures, with a high level of internal or external complexity. Optimization and analysis tools have been demonstrated to have positive benefits, increasing environmental responsiveness and optimizing performance of materials within fabricated elements.
Integration of passive and active systems for regulating building performance can be achieved through variation of material densities and geometries in response to function, enabling increased levels of sustainability within buildings. Reducing the need for heating and cooling, catching desirable breezes, increasing occupant comfort with acoustic treatment all while substantially increasing design freedom and control of the final product.
Tangible and realizable opportunities are emerging with Construction Scale Additive Fabrication Technologies combined with digital design software. These techniques could soon deliver buildings that can genuinely challenge niche areas of construction, while adding value of construction sustainability and carbon reductions. Combining the advantages of using renewable, recyclable and non-polluting material sources, reducing waste in the building process while also reducing energy use and carbon emissions with digital design opportunities in responsive design.
Some of the developers of these construction scale additive fabrication techniques will be fabricating large-scale structures within the next year and the two most developed techniques described in this paper have good prospects for future implementation within the construction industry. Construction scale additive fabrication paired with an emerging array of sophisticated CAD software for design and analysis have the potential to meet the formidable challenges of sustainability within the construction industry.
James Gardiner is the director of Faan Studio and PhD researcher for Spatial Information Architecture Laboratory (SIAL), RMIT University, Australia
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1Fabber 3D printer email@example.com
2 Discussion with developer of the BESO software, Xiaodong Huang, RMIT University