Today, the FabricArchitect looks at the letter “P”
- point supported structure
Point Supported Structures
Point-supported structures are forms with a minimum of four points of attachment with either straight or curved edges that produce a clear span with no center mast. The classic point-supported structure is the saddle shape or hypar.
Point-supported structures can have a variety of shapes depending on the number of anchor points and the position of the supporting elements, however, double curvature is essential.
Computer patterning is the process of developing a two dimensional representation of a three- dimensional membrane surface. The patterns are created with compensation factors. Compensation factors are the reduction made to a cutting pattern to allow for the expansion of the membrane once in tension. In some cases, decompensation (addition made to the length of a piece of the membrane which was shortened by compensation) is required in order to meet certain geometric conditions such as fixed points where there is no access for tensioning. The panels are sized according to the width of the fabric being used.
PVC (polyvinylchloride) or vinyl coated polyester is the most common and cost effective membrane material for both temporary and permanent tension structures. The material is soft, pliable and less expensive than PTFE. It is available in a variety of types to meet a wide range of structural requirements. It has a minimum of stretch and shrinkage in a wide range of temperature and humidity conditions and the coating process prevents mildew, stain and streaking.
Most PVC fabrics will have some form of top coating applied to keep them looking new and clean. These topcoats can be acrylic solutions, polyurethane-acrylic solutions, PVDF solution coats or a PVF film lamination. Vinyl laminated polyester is primarily used for temporary structures while vinyl coated polyester is used for both temporary and permanent structures.
PVC material has a life span of 15-25 years and comes in a variety of colors and textures. This material is sealed using radio frequency (RF) equipment.
Ouch, “Q” comes next.