Adaptable Buildings

The world is facing a gigantic construction boom, which will not be manageable with current approaches. That’s why interdisciplinary teams working in two collaborative research centres at the University of Stuttgart are looking into how novel approaches to planning, construction and engineering can help to design our built environment such that it can automatically adapt to meet changing challenges pertaining to such things as load-bearing behaviour or thermal insulation. One template from which the architects and engineers are drawing inspiration is nature.

When Konrad Zuse set about creating the world’s first computer in the 1930s, the global population was hovering around two billion people. Now, just 85 years later, that figure has risen to 7.5 billion. About 2 billion children and young adults will reach maturity in the next few years, and they’ll all need somewhere to live, jobs and shopping centres. According to Professor Werner Sobek, who heads up the Institute of Lightweight Structures and Conceptual Design (ILEK): “In the next 16 years, we’ll have to construct as much as was ever constructed up to 1930. To avoid damaging our planet beyond all repair”, he continues, “”we urgently need novel approaches that will allow us to build more with less and with the aid of which we will be able to fully reintegrate materials used in construction into natural and technical material cycles.” For, the construction industry is the world’s leading consumer of natural resources by far. It consumes the most energy, the most water, the most resources and produces the most waste.

Since 2014, architects and engineers working in Biological Design and Integrative Structures – Analysis, Simulation and Implementation in Architecture (SFB/TRR 141) at the University of Stuttgart have been collaborating with biologists and physicists at the University of Freiberg and with geo-scientists and evolutionary biologists at the University of Tübingen in a dedicated effort to identity the “underlying design and construction principles in biology and architecture”. As Professor Jan Knippers of the University of Stuttgart’s Institute of Building Structures and Structural Design explains: “Our objective is to develop multifunctional, adaptable and ecologically- efficient structures that transcend the boundaries of traditional building construction by far.” To this end, the researchers involved are taking their cue from the extraordinary variety and efficiency of natural structures and transferring the underlying principles to architecture and technology.

The “Adaptive Shells and Structures for the Built Environment of Tomorrow” (SFB 1244) collaborative research centre joined the collaborative effort at the start of 2017. Their spokesman Professor Werner Sobek wants to employ his own so-called “triple zero concept” to ensure that buildings in the future do not use more energy than they are able to extract themselves from sustainable sources (zero energy), and that they generate no damaging emissions of any sort (zero emissions) and that they can be fully recycled in natural or technical cycles without leaving any residual waste (zero waste).

Sobek had already researched this with other institutes in the past, particularly with the University of Stuttgart’s Institute for System Dynamics (ISYS), the head of which, Professor Oliver Sawodny, is also the Deputy Chairman of the new collaborative research centre. Previously, both of them had pooled their ideas in the “Hybrid Intelligent Construction Elements” research group (981), a productive collaboration which was to become the core of the current collaborative research centre. The “Stuttgart Smart Shell” was created in this context, which was the world’s first large-scale adaptable shell structure, which comprised a 4cm-thick wooden shell capable of spanning an area in excess of 100 square metres. It works because sensors continuously measure the loads throughout the structure. Three of its four support points can be moved by hydraulic cylinders, which enables the structure to adapt to unexpected loads caused, for example, by snow or strong gusts of wind, within milliseconds.

The SFB 1244 is continuing this research. 15 institutes from the University of Stuttgart and the Fraunhofer Institute of Building Physics are participating in the initiative alongside architects and structural engineers, aircraft and mechanical engineers and computer scientists. The researchers want to transfer the “Stuttgart Smart Shell” principle and investigate ways to use sensors and actuators to construct such things as intelligent high-rise buildings and bridges. Another sub-project under the auspices of the SFB 1244 involves the direct integration of socalled fluid actuators, i.e., hydraulic or pneumatic elements, into structural elements. These could then obviate the need for adaptations within the supports of the kind required by adaptive structures such as the “Smart Shell”. In another project, the team also wants to develop switchable breathability for building shells.

There is a tradition at the University of Stuttgart of catalysing innovations in the field of construction engineering through the collaboration of various disciplines. The university is the Alma Mater of such engineering and architectural luminaries as Fritz Leonhardt, Jörg Schlaich and the late Frei Otto (1925-2015), the latter of whom became only the second German to win the Pritzker Architecture Prize in 2015. Otto established collaboration in areas in which competition reigned supreme – thereby blazing a trail for those who followed: “Since the foundation of the Institute for Lightweight Structures by Frei Otto, which I took over in 1994 and merged with the Institute of Structural Design in 2000 to form the ILEK”, says Professor Sobek, “the University of Stuttgart has become a global leader in lightweight construction”. The field of “ultra lightweight construction through mechanically actuated structures”, which was developed at the ILEK is now a central component of the university's research profile.

As Professor Achim Menges, Head of the Institute for Computational Design (ICD) emphasises, another of Otto’s outstanding achievements has been the transfer of material innovations to new forms of construction. Otto took his inspiration from nature and attempted to minimise material consumption. His successors at the SFB/TRR 141 and SFB 1244 continue to work to both of these principles. We are currently experiencing a complete paradigm shift in the field of construction just as we were then, as Menges explains, whose own institute is a member of both collaborative research centres: “Without the advent of digital technologies”, he says “a structure such as the Stuttgart Smart Shell would have been inconceivable”.

The interdisciplinarity concept is also following by TRR 141 (Biological Design and Integrative Structures – Analysis, Simulation and Implementation in Architecture): “Transregio’s basic idea”, explains Jan Knippers, “is to bring scientists and engineering scientists together”. The team’s objective is to extract models for plant and animal structures from nature, to digitise them and to transfer them to the field of engineering. How the process, which involves numerous researchers from different disciplines, actually works can be understood through the example of an exhibition hall for the 2014 horticultural show in Schwäbisch Gmünd. The starting point for the work was a species of sea urchin known as the sand dollar. According to Knippers: “it lives in the breakwater and its inner structure is naturally adapted to high levels of mechanical stress.” The biologists captured it in computer tomographic images. A specially developed computer programme then converted the grey tones of the image to rigidity properties. These were then used to create a simulation, on the basis of which it was possible to work out how the skeleton of the sand dollar is arranged and constructed.

“This process follows certain rules that I can model algorithmically” says Achim Menges, who founded the Institute for Computational Design in 2008 to establish this type of process in architecture. Menges’ team programmed a digital planning tool for the sea urchin hall. Each of the plates was generated as an individual element with specific properties, based on such criteria as material restrictions, robot- based buildability and external forces. “These so-called agents” Menges explains, “wander around in the space until they find a condition in which all requirements are met. The architect designs the process, not the final form.” This results in a man-machine interaction that is beyond what either humans or computers have ever been able to achieve on their own until now.

In this case, the programme provided the data for the industrial robot, which worked out how it needed to saw, mill and drill the plates. This robotic wood processing is an innovation in itself. Next, the group built a research pavilion from these timber shell segments, which provided them with the necessary insights for the highly effi cient, self-supporting exhibition hall, whose 270 plates could be put together like a 3D puzzle and disassembled whenever necessary. “We were able to enclose a 605 cubic metre space with just 12 cubic metres of timber”, says Menges: “The shell has a span of 10 by 19 meters, but is only 50 millimetres thick”. Since then the fi rst construction projects that use the wooden shell segments have begun, so the principal has become established as an everyday construction activity. Describing the role of the researchers, Jan Knippers says: “In a highly developed industrialised nation, I see it as being our task to drive technological progress. When it has proven its value at the pinnacle then it will gradually trickle down to the broader base.”

Knippers offers the following explanation for why structures that are oriented on natural forms are superior to traditional structures: “We usually have a lot of components that we bolt together. But, the more complex the construction of a technical system, the more fault prone it is. Things jam and creak. Unless every joint is perfectly positioned exactly where it is supposed to be, there will be problems.” With the aid of bionics, this mechanical complexity is shifted to the material.

whereby one exploits two basic principles of natural forms: either an assemblage of fi bres or one made of porous structures. “In both cases it is about achieving extremely fi nely graded physical and chemical properties”, says Knippers. This is why numerous sub-projects run by TRR 141 are dedicated to the question of how one can build fl exible, adaptable structures with no joints, rollers or hinges, by applying plant movements (tropisms) to mechanical systems. Two templates for this, among others, are provided by the Venus fl ytrap and the opening mechanism of a pine cone. Such systems are more diffi cult and complex to construct, but, thanks to digital engineering, they can be used to make easier, more effi cient and more durable buildings – whilst using signifi cantly less material.

Werner Sobek estimates that it will take about a decade until all the research fi ndings have become fi rmly established in the construction industry. He expects that, in a few years, it will be possible to save up to 70 per cent of the resources currently used in construction. Time is running out: as early as the 2020s the number of people living on Earth is set to top the 8 billion mark. Daniel Völpel/amg