Extreme Living - Functional Unit Minimal Form & Efficient Structure
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Design of Ultralightweight Building Systems ¡ Jun 2017
Fig 1
Tensile Structures Mesh Relaxation
Student:
Group:
Tim Fischer
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Minimal surfaces
Mean Curvature
Workflows and Review Coming to pass the term: 'performative design', I was happy to hear about the application and the opportunity it yields. To develop a mechanically optimized system, to adequately substitute or overcome outdated or inappropriate traditional solutions, suffering common techniques strikes me as a necessary and very useful undertaking. Aiming to envision a further step on efficient tensile structures, the involved formfinding process returned numbers of spacial displacement and a certain factor of narrowing the design scope, following initial decisions as an incremental workflow. The idea to utilize the computational strength 7 already in the first design steps arose to cope with this. Realizing that the motivation disagrees partly with the extent of the course, this investigation into formulating a tool to enabling this method of a "Volume to Tensile System" became a subsidiary goal. The design task for the semester had the application of extreme living. It was thought to be situated in a thermally hostile, extremely windy environment and to host two researchers as an outpost. This temporary structure should be used as an office and be functional also as their bedroom. 120 km/h Wind load and 30 kg/m² Snow load were to be imposed into and withstood by the system. Even though this post would be well suited, built with PVC- cushions, keeping in mind the 'volume to tensile system method', it was more interesting to investigate the purely tensile system, being the less adaptable to ridged forms. This road led to the investigation of bending active combined systems, where the boundary rods keep the structural membrane tensioned and the membrane returns the favor to the rods, thus each are keeping the other from relaxing - forming a temporary tensile structure. Still working towards the tool it was possible to build an algorithm that changes a meshes anchor points on given boundaries to meet desired performance factors.
Extreme Living - Functional Unit - Minimal Form & Efficient Structure
Extensive testing and learning about the limitations of the physics engine 'Kangaroo', a Plugin for the Plugin Grasshopper for the CAD- Program Rhino 3D, succeeded in bending- active simulations for various setups with flexible closed and opened boundary curves (rods) that are fixed to a mesh (membrane) and deform combined as a system. It's necessary to mention that this simulation of behavior seems promising considering the results, but is by no means providing information about the possibility to be realized with existent materials. The calculation only takes a reduction of the 1D mesh- curves as springs (using Hooks' law) and the undirected angle deformation of the polylines (subdivided boundary curves) into account. The result showed a relationship of bending strength to membrane pretension of factor: 0.004, with a maximal displacement of: 0.202 m, for the unregular ~100 mÂł envelope. To test the results for accuracy, an incremental calculation with the FEM - Finite Element Method was necessary and Karamba 3D, another Plugin for Grasshopper was chosen to deliver such method. The difficulty to define the algorithm using the rods (possibly glass fibre- reinforced) bending strength and ideally cross sectional torsional resistance and oppose it to a shells tendency to deform into a minimal surface (as soap films do due to their surface tension) was not yet resolved for the chosen shape. Reinvestigating an already researched shape, based on a twisted box, fixed in its corners to two (end and midpoint fixed) crossing twisted boundaries, the results seemed promising, but not yet accurate. As the Semester was nearby finished, the results encompass partly fabric/ rodsseparate studies: An investigation of using the tessellation of the mesh and a pretension: initial strain: 3 mm/m, of the members as 'beams', anchoring the coinciding nodes to the not deforming rods. The fabric material: 'PVC coated polyester fabric' with 4 cm thickness was considered as the material with 4 cm corresponding cross-section diameter for the beams in this calculation. This led to a maximal displacement of 1.206 m for the Fabric. Reworking the resulting deformed beams centerlines into a mesh. Additionally, a combined approach, defining the beams stiffness only by their joints and Material: 'EGlass Fiber-Epoxy Matrix', optimizing their diameter on to 6 cm. This led to a maximal displacement of 0.321 m for the rods. Finally, the structurally relevant mathematically defined curvature was approximated on both, the physical engine (Kangaroo) related and the FEM method (Karamba) result, which leaves little difference. It would be possible and desirable to tweak the Kangaroo setup of forces closer to the Karamba (or other FEM-) related in order to follow the initial idea of setting an automated heuristic setup. This would support finding the most promising initial approaches due to varying design parameters, therefore incorporating a higher degree of achievable structures with existent building material. Before investigating the relation of the methods closer, the actual structural solution should be managed to deliver reliable results and stays the main objective, also moving forward investigating the setup of a Volume to Tensile System. Additionally to the described studies of this semester, a small exploration of force field dependent windflaw as an approximation of wind- channel- behavior/ wind resistance has been started. A first attempt to gain an overview of tent- wind resistance left the impression that 120 km/h (the definition of a Violent storm starting at 117, 7 km/h Beaufort scale) us unusually high. Most tents seem to be flown away by then and therefore the materials chosen so far should change. Secondary, the complexity of a simulation of a wind channel within the used software, the results yield only some examples on the relation of the positioning groups of posts near a coast, exposed to a general direction of horizontal wind force, leading to the impression that such cases would be well suited with only few reinforced perimeter posts or structures to deflect the exposure of the others.
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Extreme Living - Functional Unit - Minimal Form & Efficient Structure
REFERENCES 1
Bending-active structures / Lienhard, Julian, 2014
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Ongreening Pavilion / Ramboll Computational Design, completed, 2014
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StructuresLab2014 test
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Fabric pulling through avatar / Forum, Feb 2011
Shaping tension structures by actively bent linear elements / Van Mele T., De Laet L., Veenendaal D., Mollaert M. and Block P., 2013 5
Transformable active bending: A kinematical concept / S. Brancart, L. De Laet, A. Vergauwen & N. De Temmerman, 2014 6
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Strombus Gigas / Jesús Gálvez García, 2014
Fig 1 Functional
Unit / Result of the Study / 30.06.2016 Tim Fischer
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