GB734770A - Improvements in or relating to concrete floors, roofs and the like structures - Google Patents

Abstract

734,770. Reinforced concrete floors, roofs<SP> </SP>or like structures. EVANS, W. A. April 16, 1953 [Jan. 17, 1952; Feb. 26, 1952], Nos. 1339/52 and 4952/52. Class 20 (4). A concrete floor, roof or like structure is constructed by arranging in parallel a number of composite beams so that spaces or channels are formed between them, each composite beam comprising a number of beams placed end-toend in a row with their adjacent ends spaced from one another, each space between adjacent beam ends being filled with concrete in which is fixed a rigid guide member which projects laterally on both sides of the beams, and further by providing prestressing wires which stress the beams and lie outside them extending longitudinally thereof guided by the rigid guide members, finally filling the spaces or channels between adjacent beams with concrete. As shown in Figs. 1 and 3, a number of hollow relatively short beams 4 with flanges 4a are laid on intermediate temporary or fixed supports in a series of rows, the end of each short beam being spaced from the end of an adjacent short beam. Rods 6 are laid to extend in aligned spaces between the ends of the short beams across the structure and the spaces are then filled with concrete, the concrete being poured so that it partly enters the short beams to key adjacent short beams together but not to fill the hollows of the short beams completely. The members 6 are positioned so that they act as guide members to position correctly the stressing wires 10 which, as shown in Fig. 1, pass downwardly from a central position at the supported ends to a lower position near the medial portion of the composite beam. If intermediate fixed supports are provided upper bars 6 (Fig. 3) may also be provided so that the wires over an intermediate fixed support may be positioned in an upper portion of a short beam. In the end short beams 4 solid end members 7 and 8 (Figs. 5 and 6) are fitted, each having a projection 7a or 8a to fit in the hollow of the short beams. The' member 7 has a groove 7b to receive the stressing wires 10 which pass round the member 7 so that two free ends are obtained at the other end of the composite beam, these free ends being passed through channels 11 in an end member 8 and are anchored therein after being tensioned by known means. When the wires 10 have been positioned, tensioned and anchored concrete is cast in the channels between adjacent composite beams. Wrapping may be provided round the bars 6 so that they may be post-tensioned to stress the structure in a direction at right-angles to the length of the composite beams. In modification the bars may be relatively short to extend only partly across the space between adjacent composite beams, the composite beams being then prefabricated away from the site where they are to be used. In this case the bars 6 are preferably replaced by short tubes and rods or wires may be passed through the tubes so that the structure can be stressed transversely.