GB894964A - Improvements in or relating to prestressed concrete - Google Patents

Abstract

894,964. Prestressed concrete. CUFFLIN HOLDINGS Ltd. Oct. 6, 1959 [Oct. 6, 1958], No. 31879/58. Class 20(4) A device for transmitting stress from the tensioning wires to the concrete of post-tensioned prestressed concrete structures, comprises a steel tubular element provided with means for applying compression in an axial direction to concrete immediately surrounding the tube, the tubular element being encircled by a helically wound steel wire element secured thereto and radially spaced therefrom. In one embodiment the tubular element comprises an intermediate cylindrical portion 15, Fig. 4, a frusto-conical outer end portion 12 against which abuts a bearing plate 27 having conical anchorage orifices 28 for the tensioning wires, and a frusto-conical inner portion 14 which engages a tube 24 which forms a duct 25 through the concrete 26, which tube may be withdrawn after the concrete has hardened. The helical steel wire element 16 has its end portions turned inwardly to engage the tubular element 11 and be welded thereto. A flange plate 13 is welded to the extreme outer end of the tubular element 11. In another embodiment intended for use with a single tensioning wire having a conical gripping element mounted thereon, the tubular element 11, Fig. 5, of the device is ragged or serrated at 30. In a further modification a second helically wound steel wire or rod may be disposed concentrically around and radially spaced from the first helical element. Means are provided for introducing grout into the duct 25, such as an orifice 29, Fig. 4, in the bearing plate 27, or a conduit formed, on the outer surface adjacent the outer end of the tubular element, Fig. 7 (not shown), or in an enlarged portion of the outer end of the tubular element.