Membrane structure is a perfect combination of the architecture and structure. It combines the fabrics of high-intensity and flexibility together with a support system to form the stable bent surface of certain firmness, it features the space-structured formation and withstands great load from outside. Due to such advanced features as elegant shaping, lightweight, fire-resistance, ready to fabricate, quick to install, energy saving and easy maintenance, it has been widely used in various fields all over the world. This kind of structural formation is specifically suitable for the construction of large-sized stadium, advertisement board, sketch and public recreation sites, exhibition halls and shopping center.
In terms of structure forms, membrane structure can be classified into 3 forms. They are Frame Supported, Tension, Air Supported Structure 1. Frame Supported Structure
After a roof is constructed with steel structure or integrated material, tense fabric will be covered above the roof and. As the supporting structure below the roof is highly stable, the design of roof is simple and there are few limits for the position of the poen. Moreover, such structure has high profit, and could be widely used in any size space. 2. Tension/Suspension Structure
Tension/suspension structure is constructed with fabric, wire rope and supporting pole. It achieves the firm form through the tension produced by wire rope and supporting pole. Tension structure not only has creative, innovative and graceful outside appearance, but conveys the spirit of membrane structure best. In recent years, the wire cable net which is consisting of cable and compressed material and serving to support the fabric above has been largely used in the large span space. The structure has characteristics such as precise construction, powerful structure and great expressivities while it costs slightly higher than the Frame supported structure. 3. Air Supported Structure
Roof is supported by air pressure, raise indoor air pressure to a certain pressure with the ventilation system, create a pressure difference between indoor and outdoor to stand against outdoor pressure. As it is mainly supported by air pressure with the help of accessorial material of wire rope, air supported structure needs no girder or pole, therefore, more spaces would be created. The advantages of air supported structures are quick installation and high profit, but the blower needs to be run 24 hours everyday, and the higher cost as a result of continuous running and machine maintenance should be taken into consideration.
Fabric, used in construction of membrane structure,
has high strength, great flexility . It is a base cloth material made from woven fiber and with coating resin on both sides of it. Base cloth can be divided into polyester and fiberglass, resin used as coating material contains PVC, silicon and PTFE, base cloth and coating material in mechanics have characteristics as follows: Base cloth:
tensile strength, tear strength,, heat-resistance, longevity, fire-resistance Coating material:
weather protection, dirt-resistance, fabrication, light penetration
Fabric that used as membrane structure architecture can be classified into PVC fabric and PTEF fabric according to coating material. Correct selection of fabric depends on the size, function scale, application, form, aging and budget of the architecture. PVC Fabric (PVC-Coated Polyester)
PVC fabric is less expensive than PTFE in material and processing, it has many virtues of soft texture and easy construction. But it is not as good as PTFE fabric in intensity, aging, fire-resistance etc. PVC fabric is made from polyester coated with PVC. The fabric that is commonly used in architecture is produced by the treatment of coating as applying several microns acrylic resin on the surface of PVC, which is in order to improve dirt-resistance. However, after a few years, PVC fabric will generally turn yellow, and is more likely to crack. Longevity of PVC fabric is 5～8 years according to different using surroundings. In order to improve weather protection of PVC fabric, fabric, which is coated fluoric resin on top of PVC, to improve its weather protection and dirt-resistance, has been under researches and development in recent years. PVDF
PVDF is abbreviated of polyvinylidene fluoride. The material coating PVDF resin on PVC fabric surface is called PVDF. The difference between PVDF fabric and common PVC fabric is that the life span of PVDF is lengthened to 5～10 years. PVF
PVF is abbreviated of polyvinyl fluoride.fabric is laminated with lamellate PVF on top of PVC fabric. Compared with PVDF, it is more wear-resistant and dirt-resistant. But it costs more than PVDF. PTFE Fabric (PTFE Coated Fiberglass)
PTFE fabric is a material coated polyvinylidene fluoride on fiberglass textile. Comparing with PVC fabric, PTFE has great virtue of longevity, dirt-resistance and fire-resistance. However, high expense of material and processing, low flexility are the defects. In order to prevent fiberglass breaking, it requires a professional and complete plan in processing, folding, packing, construction techniques. Longevity
: PTFE of coating material is extremely stable in acid, alkali, and ultraviolet radiation conditions. It is not easy to discolor or to be broken. After several years application, fiberglass intensity and tensility remain strong. Generally, the fabric is white and has a high light penetration. The life span reaches more than 25 years. Dirt-resistance :
As coating material is polyvinylidene fluoride; surface frictional coefficient is low, thereby, it could be cleaned by rainwater and benign for the environment. Fire-resistance :
PTFE fabric is in accordance with all characteristics, stipulated in the National Fire-Resistance Testing, and it can replace other roof materials for the same purpose.