Frangible Link – A weak link intentionally incorporated in a design so that the fabric breaks lose under extreme conditions and protects the structure from failure. Permitted in some jurisdictions, usually only used on small membranes with a low importance factor.
Permeable Shade Cloth – A generic term used for knitted HDPE material. Available in grades from 10% up to >95% coverage in an un-tensioned state. Most tension membrane structures using permeable shade cloth use a grade of fabric with 90% coverage or more when providing heat, UV or other weather protection. Grades below 90% are typically used for agricultural or industrial purposes. As the name implies, impermeable shade cloth is not waterproof, however grades of 90% or more with a pitch of 10° or more usually have some rainwater run-off. The extent of rainwater run-off will range from substantial to minimal depending on the density of the fabric, the elongation under tension and the pitch of the design.
Structural Efficacy – A term we use to design a structure which is not only designed not to fail, but to also maintain it’s stiffness so as to prevent the membrane from relaxing under wind load. Otherwise structural hardware needs to be design to withstand dynamic loads and it is accepted that failure of the membrane under extreme conditions.