architectural membrane association
You will find bellow a series of questions that we at AMA considered would be the most common questions for someone who is new in tensile architecture. These questions have been answered by experts of each field. If you need any further assistance, do not hesitate to contact us and we will re direct you to one of our members.
“Through the economical use of high-quality materials and by exploiting the structural properties of spatial systems, light …. buildings can be created without significant dead weight. The construction is limited to the absolute necessities.” (Prof. Dr.-Ing. Frei Otto)
That’s exactly the secret behind Lightweight structures, few and light materials for big spans of construction. Sometimes a sqm covered area of Tensile architecture has less weight than the corrosion protection of a solid steel structure.
The membrane gets its stability out of the shape of the structure and the tension. The less three-dimensional shape one uses the higher the tension would be, leading to uneconomical structures. This means that the more shape is allowed, the better it is for the structure, and less tension is needed. Flat structures cannot be tensioned properly since it could lead to a self-destroying situation.
In principle yes, it is possible. But that would lead to a sort of textile cladding requiring a very close supporting structure. It is mainly used as temporary structure for example: tents. This has nothing to do with long lasting textile architecture.
There is almost no limit. This type of structures are used mainly for “open” buildings in the area of sport and leisure, traffic and transport, shopping malls, schools etc. Additionally, it can be said wherever sun- or rain protection is needed.
The used material (either polyester weaving with PVC-coating or glass with PTFE or Silicon coating) even though it has a weight of only 1 to 1,5 kg/sqm has a tensile strength of approx. 5 times higher than those of steel. To use this stability the membrane has to be properly formed and tensioned. This leads to long-lasting structures with a life time expectancy of over 20 years (Polyester – PVC) and over 30 years for Glass-PTFE-structures.
A properly designed and built membrane structure cost for sure more than a simple metal cladded roof. But it cannot be compared because it provides a lot more features like large free spans, high transparency, an almost unlimited number of design possibilities. Textile architecture should not be compared with simple temporary tent structures.
A properly executed project should show a well anticlastic shape and a sufficient pretension (beside those which are tensioned by air pressure). The form should secure that no water- or snow collection areas develop. Crinkles and fluttering of the membrane show an evidence of wrong force progression. On the other hand, a three-point sail should never be done, since this leads to flat surfaces. A clear load distribution into the primary structure as well as the detailing of all fixing points proof normally a good design.
A tensioned membrane structure must be designed according to all design codes valid for the region in question. Wind, snow load and sand load (ie in the middle east). The material should be resistant against the weather conditions in the area in question.
In theory yes, but it should be considered that a light-weight structure requires different construction elements. Due to the light weight it needs proper fixing against uplift by wind. Additionally, the fixing points have to cope with the high pretension forces. It is usually more economical to start the design with the idea of textile architecture in the beginning.
Yes, it is possible. It should be designed as a double layer structure with an insulation material inside. One has to consider that the translucency will be reduced to almost 0%.
A textile structure can be designed to withstand almost all wind speeds and snow loads. It’s a question of design, shape, material, supporting structure etc. In some cases, additional ropes or rope nets are necessary to stabilize the membrane against wind suction (valley cables) or too much snow load (cable nets underneath the membrane).
The strongest membrane in the market at the moment is the Type V with a tensile strength of 9.800/8.300 N/5cm in warp and weft, having a weight of approx. 1.500 gr./sqm. Although the stronger material doesn’t always mean it is the best choice, the decision for a material shouldn’t be done detached of the statics calculation. Using a stronger material than the statics have indicated could lead to an imbalance of the whole structure. Using the strongest material does not influence the lifetime expectancy of a structure, it can reduce it beside of cost inefficiency.
It is possible to have coloured membrane material. There are some standards in the market. Special colours should be tested against change by sun radiation. A special colour needs a minimum of 4.000 sqm of material to be produced.
The translucency of a membrane will depend on the thickness of the material and/or the grad of translucency which can be adapted during the coating process. For example, a normal translucency for a Type III material is approx. 10 -12 %. Taking into account that a normal living room with windows gets just 6 – 8 % of light inside, this translucency leads already to a perfect light situation where you can read your newspaper. It is possible to reach a translucency of up to 30 – 50 %.
No, it doesn’t. The coating itself together with the top coating protects the membrane during the lifetime expectancy. Anticorrosive coating is necessary for the supporting elements like steel, wood, ropes etc.
No. the materials are flame-retardant according to EN 13501-1 or the relevant codes of the single countries. This is the case for ETFE-Foil structures as well. Only some types of lighter Glass-PTFE materials are non-combustible
Tensile structures are mostly maintenance free. They should be optically checked once a year to detect possible mechanical damages caused by stormy weather or a mechanical impact. It is recommended to clean the surface from time to time just to remove the patina, if wanted.
The membranes material is very strong due to the heavy weaving inside. It very seldom happens that vandalism occurs. Strong storms can lead to mechanical damages which have to be repaired. The design should consider the risk of vandalisms, it is recommended to have the membrane start in a height of approximately 3,00 m if there is no other way of protection (like fencing etc.). If any rupture by vandalism or other mechanical forces occurs, it can be repaired by site welding in most cases. In order to avoid an enlargement of such a rupture the manufacturing company should be contacted as soon as possible, even though the resistance of tear propagation is very high.
There are a lot of full-service companies organized in AMA which can provide support from the very beginning. Beside that there are some Eng.-offices in the market which have specialized themselves in the field of textile architecture. See our list of members for more information.
If all relevant partners work on the project and no special requirements are needed, for a medium sized project with a structure of about 2.000 sqm covered area, the whole project can be finished within a time frame of 8 – 10 months. This estimate takes into account that the governmental approval works properly.
ETFE-Foil cushions including all the surrounding aluminium profiles etc. have a weight of approx. 50 % of a conventional glass structure. Due to the light weight of the material and its components it can cover larger areas without additional supporting elements. The electric consumption of the necessary blower unit is to be compared with that of a vacuum cleaner.
Research of structures which have been exposed to severe weather conditions over more than 30 years didn’t show any change in the Fluor polymer ETFE. That means the lifetime is like for normal glass roofs limited to the materials used to fix the foil cushions.
Using triple or more layers allow to regulate the grad of insulation. In this case the aluminium frame system should also be insulated. A U value (parameter that measures the effectiveness of a material to act as an insulator) of 0,78 can be possible.
Images can be printed on top of the ETFE-foils in order to get a certain shading. It is also possible to adapt movable third or fourth layers which can be moved by air pressure regulation. A third option would be to use flexible photovoltaics solar panels that can be attached to the foils and would give shade as well as produce electricity.