FabriTec Structures350 Kalmus Drive Costa Mesa, CA 92626 Tel: (714) 427-6980 Toll free: (877) 887-4233 Fax: (714) 427-6983 E-mail: inquire@fabritecstructures.com Web site: http://www.fabritecstructures.com FABRIC SHAPES AND FORMS An understanding of viable shapes and forms is essential to the design of tension structures. Support element configuration and the curvature of the fabric spanning between supports determine the basic form. The most common forms of tension fabric structures include:
Mast-supported structures are comprised of one or several peaks supported by central
poles. A compression ring or “bale” ring connects the fabric to the
central support of the mast and facilitates erection and stressing of the fabric.
Point Supported structures produce a clear span with no center mast. An exterior frame or a series of peripheral masts supports fabric peaks. 
Parallel Edge structures are another approach to creating a clear span structure.
The fabric is supported along the perimeter by parallel masts with the fabric
alternating between high and low points. The masts are held in position with stay
cables or tie downs.
Arch Supported structures also avoid interior columns in addition to introducing curved compression members as the main supporting element. For lateral stability in arch-supported systems, “cross arches” or diagonal bracing can be used. Frame-supported structures are utilized to avoid interior supports and massive footings. Fabric is attached to a structural frame and the shape of the structure is controlled by the shape of the frame. The primary structural components carry the majority of forces within the system as the fabric is used purely as cladding. 
THE COMPONENTS Following design development, a computer-generated model provides the necessary geometry and loads to begin designing the membrane, fittings and primary components. The production and details of the following components are carried out to specific construction code standards: Base Plate The base plate forms the connection between the tension membrane structure and the ground, wall, building or adjacent structural system. The base plate is usually welded to the bottom of a compression member or separated from the mast and connected to the mast with a pin connection. Mast(Compression Member) Most tension membrane structures require a compression member (mast or arch) to form a complex shape. The mast typically utilizes a welded “cleat” or “struts” to support the membrane, cable or other structural components. 
Membrane Plate / Bale ring Membrane plates provide a “link” from the membrane to the structural masts. “Bale Rings” are used at the top of conical shaped structures while along the perimeter, membrane plates are installed to accept membrane catenary cables and pin connection hardware. 
Catenary Cables/Tie downs “Catenaries” are formed along the fabric perimeter stretching from mast to mast. Each perimeter mast requires either a large moment connection or a series of cable tie downs to withstand the loads. Catenary cables are installed inside a pocket in the fabric and are usually terminated with a threaded end stub connected to the membrane plates. Tie down cables are generally attached to cleats on the top of a mast and connected to anchors installed in the ground. Membrane The membrane forms the enclosure of the structure and can be fabricated a number of ways. It can be sewn, glued, electronically welded and/or heat-sealed. There are a number of seam styles, overlaps and reinforcements available. The final fabrication geometry for all aspects of a tension membrane structure should be derived from the same computer model. Patterns created using computer generated software produces unfolded panels that represent the membrane in its stressed state. 
Specialized Hardware Tension Membrane Structure hardware consists of parts made for the yacht racing, bridge building, rigging and mountain climbing industry. Shackles, turnbuckles, spelter sockets are just a few of the hardware choices available. Most tensioned fabric structures consist of cables with threaded end fittings. Membrane plates are usually attached to primary steel components with shackles and/or turnbuckles. Hardware come in stainless steel, galvanized and custom finishes. Clamp Plates Clamp plates are normally used to provide a watertight seal along a gutter, beam or adjacent building. The material most often used is aluminum or steel. The clamp can be extruded or cast to have a distinct profile. 
WARP AND WEFT Once the form and its boundaries have been established, weave direction and seam layout are resolved. Weave direction (warp and weft) is determined by the primary curvature of the structure. Woven fabrics are usually tensioned in the weft (or fill) direction. The seam layout for patterning is determined by both the weft and warp of the weave and by appearance. Tensile structure design is the marriage of engineering and architecture and relies on the “engineer’s aesthetic” to determine the size and shape of structural components. The designer must take into account the different demands made on the engineering details during the construction of a tension membrane structure and throughout its life. STRUCTURAL ANALYSIS The next step in the design process is analyzing the structure’s response
to loads, including dead loads and live loads (snow, wind, etc.). An experienced
specialty firm should carry out a structural analysis of the proposed structure.
CONSTRUCTION DOCUMENTS Construction documents include the design and detailing of structural components; the selection and specification of fabric material; a detail and schedule of cables and hardware; and “cutting patterns” for fabrication. Engineering drawings are created first, and structural calculations are based on these. Upon approval, shop drawings are produced and fabric patterning completed. Specialized experience in handling the fabrication and erection of tension fabric structures is a critical consideration in selection of a firm for this work. Include FabriTec Structures on your design team to provide the expertise, coordination and attention to detail that results in a successful project, on time and on budget. |