Shade Sails, Covered Walkways, Umbrella Structures and other Tensile Membranes
A design and engineering company specialising in Fabric Architecture, Tensile Membranes and Shade Sails
Design and engineering of tensile membranes and shade sails

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  • Technical Terms

     

    Anchor Bolts Threaded bolts used to fasten structural members to concrete foundations. Anchor bolts can be in the form of “j” bolts or chemical anchors.

     

    Anisotropy The feature of fabric wherein the physical properties and behavior are not the same in all directions.
  • Anticlastic A surface with positive (Gaussian) curvature in one principal direction and negative (Gaussian) curvature in the other. A saddle shaped surface.

     

    Base Fabric The uncoated fabric, also known as greige goods.

     

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

     

    Biaxial Taken along two concurrent orthogonal directions, usually principal directions.
  • Boss Plate Doughnut-shaped plate attached to a cable ear plate to reinforce the pinhole and allow a thinner plate.

     

    Butt Seam Seam created when the two pieces of fabric being joined together are butted together with a strip twice the width of the seam.

     

    Catenary Cable Pocket Edge treatment in which the fabric is folded over on itself to form a pocket in which a catenary cable can be installed.
  • Catenary Cable Fitting Device attached to the end of a cable to allow a connection to another member. Fittings are swaged.

     

    Catenary The curve theoretically formed by a perfectly flexible, uniformly dense

     

    Catenary Cable Fitting Steel cables that run through the pockets on the perimeter of a tension fabric structure. The shape of the cable follows that of the pocket, which is typically curved with a ratio of 1:10. The length of the cable is determined by the project engineer supplying the fabric patterning. The thickness of the cable is determined by the engineer who calculates the reaction loads at the cable ends.
  • Clevis Devise used with a cable stud end or a threaded rod to form a pinned connection that is somewhat adjustable.

     

    Coating A material applied to a fabric for waterproofing and protection of the fabric yarns.

     

    Coating Adhesion Strength of the bond between the substrate of a fabric and the coating.

     

    Compensation The operation of shop fabricating a fabric structure of pieces of the structure smaller in the unstressed condition than the actual installed size, to account for the stretch at pre-stress level.
  • Detension Relieve the tension or stress in a membrane.

     

    Elongation The change in lengths of a material sample; normally this is associated with some load or force acting on the sample. In fabric, this elongation does not normally refer to true strain of the fiber elements as in the classical sense; but, rather, normally refers to the apparent” strain resulting from a straightening out of the crimped yarns in the fabric matrix.

     

    Equilibrium Shape The configuration that a tensioned fabric surface assumes when boundary conditions, pre-stress level, and pre-stress distribution are defined.
  • Fabric A woven cloth made of many yarns.

     

    Fabric Clamp Device for clamping the edge of a fabric panel, usually a bar or channel shape and made of aluminum or steel.

     

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

     

    Fill Yarns The shorter yarns of a fabric, which usually run at right angles to the warp yarns. Also known as weft yarns.
  • Flutter Excessive, uncontrolled movement, usually caused by the interaction between the structure and wind. This occurs when the fabric lacks sufficient pre-stress.

     

    Foundations (Footers) The large concrete anchoring structure that holds the tension structure securely to the ground. The top of the footing is typically flush with the ground level. The footing 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 footing at their precise location as indicated in the working 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.
  • Form Finding The process of determining the equilibrium shape of a fabric structure.

     

    Guy Cable The steel cable is used to support the structural integrity of the steel frame. It may be attached at the end of the steel struts to hold them together and resist them from movement relative to each other. Unlike catenary cables, 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 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.
  • Lap Seam Seam created when the two pieces being joined are overlapped by the width of the seam.

     

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

     

    Mast The principal upright in a tension structure.

     

    Membrane The fabric panels used in tension structures.
  • Membrane Plate Metal plates attached to the membrane corners used for securing the membrane to the frame.

     

    Modulus of Elasticity The ratio of the change in stress to the change in strain. Usually defined as a force per unit width of a membrane material.

     

    Node Points Intersection points of the elements used to define the fabric shape in the structural analysis; these are normally given in terms of a three-dimensional coordinate system.
  • Patterning The process of defining two-dimensional pieces of fabric, which can be spiced together to form a desired three-dimensional shape.

     

    Poisson’s Ratio The ratio of lateral strain to longitudinal strain; may take a wide range of values due to the deformation characteristics of a woven material.

     

    Pre-Stress The stress state that exists in a fabric structure when it is not acted upon by service loads; usually induced by the boundary conditions of the fabric membrane.
  • Radius of Curvature The inverse of the magnitude of (Gaussian) curvature at a location on a membrane surface. The magnitude is typically considered in two principal directions. The orientation of the principal directions and their magnitude may vary continuously over the surface.

     

    Rebar Cage A reinforcing matrix of steel rods used to strengthen concrete.

     

    Reinforcement An additional layer of fabric placed in an area of high stress to protect the main fabric.
  • Roll Goods Edge treatment in which the edge of the fabric is folded over on itself and a rope or cord is incorporated in the fold to increase the strength of the clamped fabric.

     

    Sectionalizing Method of field joining large fabric panels utilizing clamping hardware.

     

    Sleeve A tube of fabric, which loosely contains a structural element such as a cable, rod, etc.

     

    Spelter Type of cable fitting in which the strands of the cable are opened inside the fitting and molten lead is poured into the fitting to secure the cable.
  • 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.

     

    Swage Type of cable fitting in which a sleeve fits over the outside of the cable and the sleeve is compressed around the cable to form a tight fit.
  • Synclastic A surface with positive (Gaussian) curvature in both principal directions. A bubble shaped surface.

     

    Thimble Device used in a simple cable loop end to secure the cable and bear against the pin. Thimbles are usually used with shackles.

     

    Top Finish (AKA ‘Topping’) An additional coating sometimes used on fabric for greater protection against UV degradation or for ease of cleaning purposes (i.e. Ferrari’s PVDF branded T2 , Dupont’s PVF branded Tedlar).
  • Turnbuckle Threaded device used with cables or rods to allow adjustment.

     

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

     

    Uniaxial Taken along one direction, usually a principal direction.

     

    Warp Yarn The long straight yarns in the long direction of a piece of fabric.
  • Weaving The process of making a fabric from yarns passing alternately over and under each other.

     

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

     

    Weldment Connection component, usually steel, for the attachment of cables and/or fabric. If may be free-floating or connected to other membranes.

     

    Wicking The conveying of liquid by capillary action along and through the yarns of the base fabric.
  • Wire Rope Clip U-shaped bolt with special insert, specifically designed to clamp a wire rope to itself when forming a loop end for temporary cables.

     

    Wrinkles Furrows or ridges on the normally smooth surface of a fabric structure, which are indicative of extreme differences between the principal stresses typically resulting from a lower stress perpendicular to the furrow.

     

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