Abstract: This invention relates to large reflectors in particular those used for antennas, solar mirrors and the like having a concave reflector surface. The reflector comprises a membrane having a reflective surface, which membrane in its initial planar state is capable of being deformed in all directions in its plane. The reflector is mounted in a gas-tight chamber as one wall thereof and a differential pressure is exerted across the membrane either by way of increased or reduced pressure applied to the chamber. When deformed to concave shape, such deformation may be sufficient to cause permanent deformation of the membrane to its concave shape when it has been stretched beyond its elastic limit and plastic deformation has occurred. The reflector may then be used removed from the gas-tight chamber and when so used is preferably backed with a rigid foam backing.

Abstract: A waisted envelope for tubular building structures, such as cooling towers, is supported by way of a supporting structure, joined with its top end and responsible for a pulling or pretensioning force, on a system taking up the vertical component of the pulling force. The envelope is designed as a membrane made of material designed for supporting tension within its plane in all directions.

Abstract: The invention relates to a structure, such as a cooling tower, comprising a waisted tubular envelope consisting of a membrane made of a material which is capable of supporting tension in all directions in its plane. The membrane is pre-tensioned and carried with its tubular axis upright from a support which provides the vertical component of the pre-tensioning.