Lightweight constructions - membranes such as an tensile structure or membrane, an air cushion roof, canpoy, etc. - are from ecological point of view interesting because material properties and natural resources are used optimally. Furthermore they form an enrichment of architecture in most cases.
The main point at forming most constructions is a light (fragile) possible design. Its own weight in relation to the carrying mass should be as low as possible. Nature strengths are the enemy of lightweight constructions. Snows and wind charge (and as a result arisen ultrasounds) but also temperature oscillations, can be of large influence.
The Diagram below shows a simplified overview of compressed tensioned constructions.
Poly-Ned - Lightweight constructions, compression of tensioned constructions
source: The Design of Membrane and Lightweight Structures - Marijke Mollaert / 2002 |
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Many designs are imagineable. The design of the possible support construction and transfer of forces plays an important role. The overview mentioned below gives an idea of possible (also double curved) shapes cq. basic ideas. During the design process such shapes are often the beginning of the project. These `discussion pictures' will lead - with all criteria which are valid for that for that specific situation - to an idea or concept which can be developed further to an definite design.
| Possible (also double curved) shapes or basic ideas |
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CAD is often applied for technical drawing work. Visualization of possible solutions can be displayed by use of specific software. In some cases, a model has to made in order to visualize the three-dimensional image as completely as possible and to check for feasibility.
| Model of of a movable tensile structure |
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| Computer animation of a movale tensile structure |
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Materials
Poly-Ned has a a large scope of textile materials available for tensile structures. There are different producers with each their own specialisms. Also can be developed or adapted a custom made material if necessary. Poly-Ned work among others with producers such as Ferrari, Verseidag, Heytex, Besouw, etc.
| Some examples of membrane materials |
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| Coated pretensioned,plain weave cloth |
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Each tensile/ tensioned structure requires a specific choice of materials. The principles for the required mechanical strength, UV resistance, etc., are design and the location of the tensile structure (wind, and sun?).
Poly-Ned applies a lot of PVC coated polyester fabrics, Teflon / PTFE coated glass fabrics, silcon coated glass fabrics and ETFE foil (100% transparent Teflon without reinforcement) and polyurethanes. There are additional / other coatings possible.
PVC gecoate polyester weefsels en Teflon/PTFE gecoate glasweefsels zijn de meest toegepaste materialen. De levensduur van PVC/polyester is 15-20 jaar, Teflon-glasweefsel kan langer meegaan mits het op de juiste manier wordt verwerkt. Teflon heeft daarnaast nog de eigenschap dat het zeer vuilafstotend ofwel zelfreinigend is. PVC-polyester is flexibel en laat zich gemakkelijk verwerken; Teflon-glas is daarintegen breukgevoeliger en juist lastiger te verwerken.
PVC coated polyester fabrics and Teflon PTFE coated glass fabrics are the most commonly used materials. The lifetime of PVC/ polyester is 15-20 years, Teflon-glass fabric may last longer if it is properly processed. Teflon also has the property that it is very dirt repulsive or self-cleaning. PVC-polyester is flexible and can be easily handled, Teflon-glass is more crack-sensitive and more difficult to process.
Fixation and details
Each stretched spankap or canopy has its own specific details. Where possible Poly-Ned applies (own) standard developed tensioning device systems. Where this is not possible, in consultation with the client / architect & designer, a whole new system will be developed with the engineers of Poly-Ned to finally obtain the result that is desired.
| Advanced sketches of (in-sight) fixations |
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Detailing starts often with the creation of sketches, as indicated above. This creativity leads then to the digital design of a detail. Below you can find a picture of a three-dimensional top detail. This is a rendered view of a digital CAD drawing.
| 3-dimensional view of top detail |
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Structural constructions
Poly-Ned streeft ernaar het membraan met een zo licht mogelijke draagconstructie uit te voeren, zodanig dat het doek volledig tot zijn recht komt. Esthetisch gezien is de dragende constructie veelal ondergeschikt aan het membraan. Materialen die kunnen worden toegepast als draagconstructie zijn staal, aluminium en (gelamineerd) hout.
Poly-Ned seeks a membrane combined with a structural frame - as light as possible, so that the fabric prevails estheticly. Aestheticly, the structural design is often secondary to the membrane. Materials that can be used as support construction are steel, aluminum and (laminated) wood.
Back to Tensile Structures
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