Upcycling Space Structures (Preface to special issue)

The construction industry’s contribution to the deterioration of Earth’s ecosystem is huge. 11% of all anthropic greenhouse gas emissions worldwide are due to the construction, demolition, and transformation of buildings and infrastructure. Construction and demolition waste are the largest waste stream by volume and weight in the European Union making up about a third of all waste produced – other continents follow the same trend or are doomed to follow it in the near future. The construction industry contributes to both natural resource depletion and the degradation of ecosystem services. By 2050, 70% of the world’s population will live in urban areas: growth and densification of cities will accelerate the obsolescence of buildings, leading to their premature partial or full demolition. The structural designers’ toolset to tackle this multi-faceted environmental challenge traditionally consists in (1) avoiding waste and new production by re-assessing and/or improving existing structures; (2) reducing newly-produced material volumes by optimizing structural layouts and sizing; and (3) substituting classical materials with low-carbon alternatives – e.g. bio-based or recycled materials. While these three strategies are necessary, they are not satisfactory. The current special issue explores the potential of a fourth strategy, consisting in designing new structures, and in particular space structures, made of reused components. Contrary to recycling, the aim of component reuse is to avoid reprocessing material and to make the most of the geometrical features and mechanical capabilities of given products, while extending their lifespan. In other words, component reuse aims at designing structures that upcycle waste generated elsewhere. From sorting out the inherent variability of a reusable set of components, to dealing with the incomplete description of their predefined capabilities, the change of paradigm triggers a series of new design tasks that are yet to be supported by appropriate algorithms and computational tools. More importantly, a whole new world of design opportunities opens up. The papers in this special issue address these challenges and opportunities frontally. The first one explores the reuse of steel or timber bar members in spatial truss layouts. It is authored by J. Brütting from EPFL, and P.O. Ohlbrock, P. D’Acunto, and J. Hofer from ETHZ. The second one studies the reuse of non-standardized metal sheets for corrugated shell structures. It is authored by S.M. Moussavi, H. Svatoš-Ražnjević, A. Körner, Y. Tahouni, A. Menges, and J. Knippers from the University of Stuttgart. The third one deals with the reuse of small timber pieces for reciprocal floor systems. It is authored by D. Parigi and L. Damkilde from Aalborg University. The fourth one addresses the reuse of thin strips with rectangular sections – e.g. skis – in elastic geodesic gridshells. It is authored by C. Haskell, N. Montagne, C. Douthe, O. Baverel from ParisTech, and C. Fivet from EPFL. The fifth one considers the reuse of magazines to form structural membranes. It is authored by A. Le Pavec, S. Zerhouni, N. Leduc, K. Kuzmenko, and M. Brocato from the ENSA Paris-Malaquais. The idea of this special issue emerged during discussions within the Working-Group 18 on “Life-Cycle Design and Assessment of Shell and Spatial Structures”, hosted by the International Association for Shell and Spatial Structures (IASS), and chaired by the guest editors of this issue. We thank the IASS for their support and invite all interested readers of this IJSS issue to join Working-Group 18, as we will continue generating fascinating discussions on upcycling structures. Waste – whose etymological root *h1weh2- means “to leave, abandon, give out”– is a transient state and must urgently be reclaimed by structural designers. Because of its ubiquity, diversity and historical marginalization, waste upcycling in structural applications is a source of yet untapped technological developments. By providing a ready-to-use, time-proven mechanical behavior, upcycled waste presents a one-of-a-kind industrial value. By exhibiting non-duplicable physical traces of its prior purpose or of wear and tear, upcycled waste can have more cultural or aesthetic value than any newly-manufactured materials. By avoiding the production of new materials, upcycled waste presents a unique potential to alleviate global warming and resource depletion. In short, waste may be of higher value for future human developments than any other construction material. It is the structural designers’ and researchers’ current duty to make this possibility a reality.

Reuse in Architecture & Structural Design

Jan Friedrich Georg Brütting

Introduction The construction industry has an extensive impact on the global environment and will be facing three big challenges in the next decades: reducing its resource consumption, decreasing its energy use, and limiting its waste production. This is even more crucial, considering global population growth and increasing urbanization. Consequently, a shift of paradigm from a linear economy of make-use-dispose, towards a circular economy that advocates closed loops within the service life of materials and components is required. Recycling currently is the common strategy to make use of obsolete materials; however, it involves energy for reprocessing (e.g. melting steel scrap). Instead, direct reuse of components close to their original form has the potential to reduce environmental impacts further because sourcing additional raw material is avoided and only few energy is spent for transformation [1]. In the case of buildings and infrastructures, load-bearing systems contribute the most to the embodied environmental impacts. This is because of their big mass and energy intensive construction process. These observations suggest that reusing structural elements has large potential to reduce the environmental footprint of building structures. Reused components may consequently have a longer service life than the systems to which they initially belonged and disassembled buildings become a mine for new constructions. This idea is of course not a today’s invention, but has found application already far in the past as well as in recent building projects. Before industrialization, most building materials were sourced locally and reuse of building materials and components was the rule because it was more cost and time efficient than new production [1]. The scarcity of building materials had to be considered in design and construction. A classic example is the reuse of bricks throughout the Roman and Greek eras or in post-war times. Remarkable are also the stone columns of the Great Mosque of Cordoba, Spain, which were reused from nearby Roman and Visigoth ruins to support Moorish double arches (Fig. 1a). More recently, the steel structure of the BedZED project in London (Fig. 1b) was constructed from 90 % locally reclaimed elements [2]. Many other contemporary case studies in which bricks, timber, or steel elements have been reused are reported in [1] and [2]. An outstanding structure is the London Olympic Stadium (Fig. 1c), whose roof truss incorporates 2000 tons of steel pipeline tubes reused from a nearby development project [3]. At smaller scale, a strained grid-shell pavilion made of reclaimed skis has been built by the researchers at EPFL’s Structural Xploration Lab (Fig 1d). Recently this environmental-aware architectural and structural design is evolving. In addition, governments have understood the potential of circular economy and circular design. For instance, the European Commission has issued an EU action plan for the circular economy in order to reduce waste and landfill. Research While historic and contemporary projects, especially in Europe, highlight the environmental, time or cost benefits of building with reclaimed (structural) elements, many technological challenges remain. Buildings have to be carefully disassembled, which is often only possible for steel or wooden structures that are joined with reversible connections, or when elements can be cut and member ends are reshaped to fit new settings. Further, the quality and structural capacity of reclaimed elements has to be ensured. Under these assumptions, this research focuses on the standpoint of composing building structures from a stock of reclaimed elements. This entails reversing the conventional design process. The constrained availability of elements dictates the layout (topology and geometry) of the designed structure due to the a-priori set geometric and mechanical properties. The design shifts towards a “form follows availability” paradigm [1]. Structural optimization methods, which traditionally seek best performing structural systems under given boundary conditions, can be extended to integrate and facilitate element reuse in structural design. This research uses the combination of combinatorial optimization and form-finding methods to design reticulated structures from a given stock of reclaimed elements [4], where: 1) available elements are grouped by material, structural capacity and dimensions, 2) an optimal assignment of a subset of stock elements into a structural system is performed, and 3) the structure geometry is optimized. Generally, the assignment step 2) minimizes the structural weight to optimally utilize the available element capacities, whereas the geometry optimization step 3) is carried out to match truss geometry and available element lengths. This method is applied to optimize truss systems subject to differently composed stocks. In each case, varying cross section sizes or element lengths result in a different outcome of the designs. Figure 2 (a) shows a typical roof truss design, which is loaded at the top chord and is used as the initial topology for the introduced optimization method. The obtained layout for the case of using Stock A is reported in Fig. 1b. This stock consist of elements with 3.00m length which are n = 4 times available for each of the six cross-section groups. The use of the stock is indicated by the superimposed magenta colored bars on top of the grey ones. Due to limitations of the stock to 3.00 m elements only, the truss layout contains two arrays of three almost equilateral triangles. For the truss made from Stock B, which is composed of equivalent cross section groups but with variable element lengths, the found geometry is shallower and vaulted. In both cases, the geometry optimization allows to use most of the stock members with their full length. The exploration of these case studies concludes that the availability of elements has a significant influence on the final structural design as well as its structural performance. For example, if an insufficient amount of elements with small cross-sections is available, the structure will be oversized (i.e. the capacity of available members is not utilized) and environmental savings are diminished. Conclusion The proposed optimization and form finding method renders a first step towards facilitating the design with reused elements where the outcome is not as predictable as in the well-established conventional structural design process. Future research will extend this method towards different structural typologies such as bending and frame systems. Further, the question of customized connection details enabling the joining of stock elements has to be addressed.

2018

Reconsidering traditional timber joinery for sustainable structures

Jan Friedrich Georg Brütting, Corentin Jean Dominique Fivet

Timber construction plays an important role in architectural history, in modern construction methods and in sustainable design, for which wood-only joinery techniques have been used for centuries. Traditional joinery typologies are the product of successive, empirical improvements over generations of artisans [1]. However, over the industrialization era, many traditional wood-only construction techniques were abandoned in favor of more profitable connections with mechanical fasteners [2]. This shift of practice lead to the development of connections with quantifiable capacity but neglecting the intrinsic anisotropic properties of natural timber. Specialized knowledge of carpenters and typical building traditions were lost. Yet, examples of historic timber buildings with a life span of multiple centuries have demonstrated many advantages of interlocking timber joints, e.g. in severe loading cases as in the case of earthquakes [2]. New technologies and recent developments in digital fabrication allow the custom and automated manufacturing of traditional wood-only connections for new buildings [3]. A big potential of such contact-only connections is their fast assembly and non-destructive disassembly. Remarkable examples include the Japanese Ise-Shrines, which are rebuilt in a 20-year frequency for the past 1300 years. Traditional joinery techniques allow for sustainable solutions through the replacement, long-term maintenance and repair of structural elements [4]. They also ease recycling and energy-recovery. In times of global environmental problems where the building sector is highly responsible for resource depletion, greenhouse-gas emissions and waste pollution, these advantages will become even more important for regenerative architecture or transformable building design. Buildings need to become more adaptable to frequent changes in ownership or use to avoid superfluous demolition. For example in Japan in the past, entire cities made from timber were constructed for disassembly and transport in order to accommodate for recurrently changing administrative centers [3]. Some joint typologies were designed to allow the later vertical or horizontal extension of buildings [2]. In Japan also, contemporary buildings are not understood as permanent edifices but as structures made to be replaced or removed. This could only be achieved through highly developed timber joinery techniques. A combination of traditional joinery with contemporary post and beam construction and CNC prefabrication is already well established in Japan in the construction of residential buildings [3]. However, a straightforward application of traditional joinery techniques in today’s construction is not always possible. In the past, the structural integrity of traditional joinery techniques was proven mainly through in-situ, de-facto testing. Today, building codes include little-to-no information about the application of wood-only carpentry connections in comparison to those with mechanical fasteners [2]. Research on interlocking joints concentrates on a very precise analysis of few different joint typologies. There are limitations in literature in terms of analyzing a variety, or a library of ancient interlocking wood joints to develop an extensive relative comparison between them. As a first step, the present research initiates a FEM campaign to catalog a library of Asian joints. To align traditional techniques with modern construction and typically used North American timber, solid Douglas fir was considered as the material. The goal of the analysis is to extract the relative capacity and stiffness of different joints to understand their mechanical behavior. This comparative record, which should be extended to additional Asian and European joint types, will allow academics and designers to push the capabilities of these ancient techniques while benefitting from modern materials, construction techniques and fabrication tools. Other research will also address the optimization of joint geometries to customize demanded capacity or stiffening. In addition, Life Cycle Assessment of constructions with conventional and advanced traditional joinery technology will be carried out to quantify potential environmental savings.

2018

Low Carbon Pathways for Structural Design

Catherine Elvire L. De Wolf

To avoid an increase in greenhouse gas emissions, a depletion of resources, and waste accumulation, structural engineers have a major role to play in low carbon structural design. For example, cement- based materials represent one-third of all materials extracted each year [1]. This paper offers three pathways for lowering the embodied carbon of building structures – the emissions related to material extraction, production, transport, construction, maintenance and demolition – through the lens of three case studies of building structures in Switzerland. The first pathway focuses on the structural scale by reducing material intensities in terms of material use per unit of floor area. The second pathway focuses on the material scale by lowering the impact of the materials themselves through the choices of the materials typically used in structures. The third pathway focuses on potential changes to current construction practices by (re-)introducing reuse strategies in the building sector. A simplified version of Life Cycle Assessment (LCA) is used to evaluate each Swiss case study compared to current practice. The material quantities are collected from literature, architectural drawings, Bill of Quantities (BoQ), and Building Information Models (BIM). This research illustrates the challenges and opportunities of three pathways for low carbon structural design: the optimization of material efficiency, the use of low- carbon materials, and the reuse of structural elements from other demolition sites.

2018

Reuse in Architecture & Structural Design

Jan Friedrich Georg Brütting

2018

Reconsidering traditional timber joinery for sustainable structures

Jan Friedrich Georg Brütting, Corentin Jean Dominique Fivet

2018