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. An exterior frame, adjacent building or perimeter masts with or without tie downs support the fabric. 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. Several point-supported structures can be combined by sharing a common mast. The membrane can also be supported from above at specific points by cables or rods coming off the perimeter masts or higher points on a building. They can also be designed as repeated modular units and in combination with mast-supported or arch-supported structures to create unique and larger spaces.
Another approach to creating a point-supported clear span is by supporting the membrane along the perimeter by a row of masts. In this case, ridge cables which carry gravity loads hang much like a suspension bridge between masts while valley cables which resist uplift forces form an arch half way between the next rows of masts. The perimeter masts are held by safety and tie down cables. When the masts are arranged in a linear fashion, the result is a series of alternating high and low points along the perimeter. When the masts are arranged in a radial pattern, a star shaped structure with either a low or high center is created.
These structures can be used for tents, awnings, canopies and umbrellas to name a few.