GB709678A - Improvements in or relating to reinforced concrete structures - Google Patents

Abstract

709,678. Reinforced concrete. PRE-FACT CONCRETE, Ltd. May 11, 1953 [May 15, 1952], No. 12274/52. Class 20 (4) A prestressed concrete floor or roofing span consists of U- or box-shaped lightweight foamed concrete elements 1 which are laid, if necessary as aligned sections, in spaced relationship, in the direction of the application of the prestressing force, and dense in situ concrete 2 is applied to their upper faces, the prestress being applied, when the concrete is set, by screwed rods 8 and end plates 11. The dense concrete 2 is reinforced with mesh 4, and the rods 8 are passed through a passage formed in the concrete by an inflated tube, or are prevented from bonding with the concrete by a bituminous coating. The elements 1 are temporarily supported on scaffolding until the concrete 2 has set. Keying grooves 7 are provided. Where the structure passes over a door or window opening or is formed with a roof parapet portion, Fig. 4, the dense concrete is thickened at the ends 18 and is prestressed by post-tensioned rods 19. The width of the legs 2 may be increased at the ends of a long span by using at those positions U-elements which are narrower. In modifications the spaces between the elements are closed by flanges on the bottoms of the limbs of the U-elements, or by foamed concrete tiles or strips. The elements 1 may be apertured for the transverse passage of electric or other conduits. The underside of the elements may be plastered, rendered, pointed or closed in with sheeting nailed to the elements.