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Anticlastic A surface with positive (Gaussian) curvature in one principal direction and negative (Gaussian) curvature in the other. A saddle shaped surface (Pringle).

Bias Oriented at 45-degrees to the warp and fill directions of the fabric.

Biaxial Taken along two concurrent orthogonal directions, usually principal directions.

Cable Fitting Device attached to the end of a cable to allow a connection to another member.

Cable net Surface structure composed of discrete cables connected at crossing points usually used in fabric architecture to create an ETFE roof structure.

Catenary The curve theoretically formed by a perfectly flexible, uniformly dense, inextensible cable suspended from each of two end points. In fabric structures experience, this shape is probably not ever truly developed, but is commonly used to describe the shape developed at the boundary of a uniformly stressed fabric structure attached to a cable which is restrained only at its end points.

Catenary Edge Method of securing the edge of a panel with a cable tensioned between two fixed points.

Coating A material applied to a fabric for waterproofing, protection of the fabric yarns against UV degradation or for ease of cleaning purposes

Creep An increase in strain in a material with time when subjected to a constant stress.

Cushion Membrane structures in which the surface is prestressed and stabilized by air pressure. Typically multi-layered and used as the structural system of ETFE films. Utilizes an electric pump system to maintain the pneumatic pressure.

ETFE Film Transparent membrane material consisting of ethylenetetrafluoroethylene film.

Fibre The basic thread of the material from which the yarns and fabrics are made.

Flutter/flapping Excessive, uncontrolled wind induced movement of a surface. This can occur when a tension membrane lacks sufficient prestress or curvature and will lead to wearing and failing of the fabric.

Foil Term generally applied to isotropic structural membranes such as ETFE film. Strict use of the term applies only to metallic membranes.

Form Finding (Form Generation) The process of determining the equilibrium shape of a fabric structure using computer aided design systems

Foundation (Footing) The large concrete anchoring structure that holds the tension structure securely to the ground. The top is usually flush with the ground level. The foundation is comprised of a matrix of steel rebar that is referred to as a cage. The concrete is poured into the hole in the ground that holds the cage. The anchor bolts get placed into the top of the foundation at their precise location as indicated in design drawings. A certified engineer must calculate the size of the footings. The size of the footing must contain enough weight to hold down the tension structure for the wind loads in the area.

Guy Cable This steel cable is used to support the structural integrity of the steel frame. It may be attached at the ends of the steel struts (or arms) to hold them together and resist them from movement relative to each other. The lengths are calculated by a straight point-to-point dimension. The engineer will need to determine the thickness by calculating the maximum stress on the cable.

Keder (Keder Edge) Brand name for the solid PVC cord used at a ‘rope edge’. Rope edges provide strength and a surface to evenly distribute fabric tension forces.

Light Transmission A measure of the portion of light striking a fabric surface that passes through the fabric and into the space to provide daylighting.

Mast The principal upright in a tension structure.

Membrane A surface structure with no bending resistance and therefore capable of resisting only in-plane tensile forces.

Pantone A set of standard colours for printing, each of which is specified by a single number. You can buy a Pantone swatch book containing samples of each colour

Patterning The process of defining two-dimensional pieces of fabric, which can be spiced together to form a desired three-dimensional shape.

Permeant As used throughout this website refers to a structure that is designed to withstand the all year round weather conditions for the location in which it is to be installed. It does no therefore need to be taken down in the extremes of the climate.

Ponding A progressive failure of the membrane caused by accumulation of snow, rain, or combined loading resulting in changes to the surface geometry that prevent drainage of the accumulated material and cause changes to the integrity of the membrane that can not be reversed.

Prestress The state of stress in a membrane structure in the absence of all applied loads; usually the result of strain energy intentionally stored in the system through jacking or tensioning during installation.

PTFE Polytetrafluoroethylene, commonly known by its trademark name Teflon. This coating is applied to a fiberglass scrim to produce a high strength tension structure fabric membrane with a life expectancy of thirty plus years. PTFE may also be expanded and woven into a fabric that can be coated with a fluoropolymer to create a high strength architectural fabric.

PTFE Glass Fabric Woven glass fabric coated with PTFE. Also referred to as PTFE coated fiberglass.

PVC/Polyester Woven polyester fabric coated with polyvinylchloride (PVC). Often provided with an additional topping.

PVC Polyvinyl chloride, properly mixed with plasticisers for flexibility and applied to a polyester scrim makes for a high strength and popular tension structure fabric membrane.

RAL a colour matching system used in Europe. Usually refers to the RAL Classic system, mainly used for varnish and powder coating but nowadays there are reference panels for plastics as well

Scalloped Edge Refers to an edge detail of membrane construction wherein surface membrane terminates into a flexible edge cable stretched between fixed points.

Silicone/Glass Woven glass fabric coated with silicone.

Stay Cable A steel cable that is used to stabilize the mast in response to the forces created by wind loads. The stay cables are used to resist movement of the structure relative to the earth. One end of the cable will typically connect to the end of the steel frame near the fabric connection. The other end will terminate to a sturdy section of the mast or a footing in the ground.

Synclastic A surface with positive (Gaussian) curvature in both principal directions. A bubble shaped surface.

Top Finish (or Topping) see coating

Translucency – See light transmission.

Ultraviolet (UV) Degradation The deterioration of a fabric under long-term exposure to sunlight. Coatings on the fabric will help prevent UV degradation.

Warp Yarn The long straight yarns in the long direction of a piece of fabric.

Weft Yarn The shorter yarns of a fabric, which usually run at right angles to the warp yarns. Also called the fill yarns.

Wicking The conveying of liquid by capillary action along and through the yarns of the base fabric.

Yarn A number of fibers grouped together to make a thicker strand for weaving. They may be twisted together or parallel to each other.

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