KET Hello Wood Festival 2016

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KET Form-Active Hybrid Structures Form-active hybrid structures (FAHS) couple two or more different structural elements with low stiffness (such as slender beams, cables and membranes) into one structural assembly of high stiffness. They offer high load-bearing capacity at a fraction of the weight of traditional building elements and do so with a clear aesthetic expression of force flow and equilibrium. The exploration and development of form-active hybrid structures is important because of their potential to improve the performance of buildings in terms of efficiency of material usage. Actively bending slender natural materials and combining them with other materials into stiff structural hybrids has been prevalent in vernacular architecture since the beginnings of human dwellings and homes. Reference is made to the traditional Mudhif in Afghanistan and Iranian felt tents below. In terms of construction this is not new technology, however in terms of design tools there is great potential for novelty and innovation.

Fig.: Erection of a Mudhif, Oliver, P.: Dwellings: The Vernacular House World Wide

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Fig.: Atabay Yomut, Amirkhani, A. et.al: Iranian felt tents: An architectural heritage of the Turkmen

The design of hybrid structures is limited by one significant restriction: The geometry definition, form-finding and structural analysis are typically performed in separate and bespoke software packages which introduce interruptions and data exchange issues in the modelling pipeline. This interdependent behaviour adds substantial complexity to the process of design which typically limits hybrid structures to simple topologies (e.g. membrane restrained column/arch). The full potential of hybrid structures can only be unlocked with a tool which simultaneously facilitates their design in a geometrically flexible environment (i.e. Grasshopper) and which provides immediate feedback to the designer in terms of structural performance (i.e. Kangaroo2). The mechanical precision, stability and open software architecture of Kangaroo2 has facilitated the development of proof-of-concept modelling pipelines which can tackle this challenge and offer a powerful form of materially-informed sketching. At the SmartGeometry2016 workshop in Gothenburg these tools were put to the test to great success. Form-active structural hybrids were designed and built within just a few days at the SmartGeometry workshop using slender (6mm diameter) GFRP rods. A 6m tower was designed and built which was extremely stiff and lightweight and validated the methods being tested.

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Berlin University of Arts Proposal The Berlin University of Arts plans to implement these novel digital tools as an academic elective course for bachelor and master students studying architecture. Focus will be put on parametric design using the developed tool. A lecture series and design critiques will be held. The underlying design objective for the students will be based on the Hello Wood theme of Settling: Rituals of Arrival. Our student group will design settlement - concepts based on the principals of FAHS. We consider these hybrid structures as a temporary and flexible answer to the dynamic ritual of arriving and settling. Final designs cannot be presented in this proposal as they have not yet been completed by the students. Our group is made up of approximately 12 students. We hope that the images from the SmartGeometry workshop provide sufficient impressions of the type of structure that we will be building at Hello Wood.

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Slender timber sections of pine or hardwood (preferred) Ø 1 cm Total length 300 m (individual lengths as long as possible)

Strapping / packband 13.00 x 0.55 mm http://www.rajapack.co.uk/packaging-tape-strapping/strapping-accessories/corded-polyester-strapping_OFF_UK_0030.html

Brackets http://www.rajapack.co.uk/packaging-tape-strapping/strapping-accessories/semi-open-metal-seals_OFF_UK_0034.html

Sealers http://www.rajapack.co.uk/packaging-tape-strapping/strapping-accessories/sealer-12-16mm-strap_OFF_UK_0135.html Staplers

Additional tools and materials TBC

KET Modelling Methods Assembly definition is based on a set of rules, or rubrics, for how the designer is to construct the geometrical representation of elements, a method for discretizing this geometry and methods for dynamically coupling the Rhino document and the Grasshopper definition. Beams and cables are represented as polylines, piecewise linear curves which may approximate continuous shapes. These are drawn by the designer as coarse polylines describing assembly topology and initial dimensions. Implementing a layer naming convention, these are automatically piped to Grasshopper if anything changes on the Rhino document beam/ cable layers. Here they are discretized by subdividing their edges into a user defined subedge length. To enable the designer snapping to the discretized geometry, all its vertices are automatically captured and sent back to the Rhino document as a locked point cloud. This modelling loop affords immediate and precise definition of assemblies.

Definition/drawing of self-connecting beams. The rubric for a non-periodic end-end connection is to draw overlapping vertices at the connection, or, to have the incoming edges meet below a user specified angle.

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The shaping process implements the Kangaroo2 (K2) dynamic relaxation solver. K2 is based on projections onto goals. A goal is a behaviour which, given the current positions of a set of points, calculates a set of vectors for how these points should be moved. This may include a weighting factor determining goal strength/stiffness. K2 has several properties which has been integral to our research: 1) The API is designed for implementation through scripting, enabling development of custom, minimal and optimised pipelines using IronPython. 2) Goal weights can be set arbitrarily high and remain stable, enabling the modelling of stiff materials with fast convergence. 3) The bending goal implements the resolution independent Adriaenssens and Barnes model, enabling the shaping of non-uniformly discretized elastica beams. Shaping has three sub-processes: defining, solving and refining goals. Defining goals implies generating local K2 goals along the discretized polylines which yield overall element behaviour. A beam is represented by a goal for each edge maintaining its length and a goal for each vertex and its neighbours which attempts to keep the angle formed by the three at 180 degrees. Combining these goals enables accurate elastica behaviour. Cables are represented by edge-length goals. Minimizing these, their shaping behaviour is similar to membrane shaping. If two elements share vertices/edges they are connected at these sub-components. Goals are passed to the K2 solver which iteratively shapes the assembly until equilibrium. Any change in input (topological or numerical) will trigger this solve-equilibrium loop. This enables the designer to interactively explore shaped assembly topology, and, dimension elements by refining goals values.

Interactive shaping and dimensioning pipeline using Joey/Kangaroo 2 (CITA 2015)

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Interactively defining topology and shaping an FAHS assembly with real-time shaping and downstream bending analysis using our modelling pipeline

Example of quickly sketching topologically different FAHS assemblies. The assemblies are projected