GB642360A - Improvements in or relating to the stressing of the reinforcing means for prestressed reinforced concrete - Google Patents

Abstract

642,360. Reinforced concrete. MINISTER OF WORKS. June 16, 1948, Nos. 16226/48 and 13221/49. [Class 20(iv)] In a gripping device for tensioning reinforcing wire in concrete work, the lateral pressure exerted by the gripping surfaces increases towards the unstressed end of the wire, the tensile load being thus uniformly distributed along the gripping surfaces. The wire 2 is gripped by a taper pin 4 in a tapered hole 3 in the anchoring means 1 which is stationary, or moved by a jack to the right. The pin is formed with a flat 4' serrated or roughened to facilitate gripping. The line joining the tops of the serrations tapers more than the hole 3, e.g. so that with a wire of 0.104 inches diameter, the difference in the tapers is 0.012 inches over a length of one inch. When tension is applied to the wire, the difference in the coefficient of friction between the serrations and the wire, and between the wire and surface 1A causes the pins to be drawn further into the hole. The section of the taper pin and the number of wires held thereby may be varied. As described above, the wire is bent through an angle equal to half the angle of the taper pin, but this may be avoided by inclining the axis of the pin at an angle equal to half the angle of the taper pin to the direction in which tensioning takes place. In the case of a multi-holed plate anchor, the axis of each of the tapered holes is suitably inclined. In another construction two wedge-shaped rectangular jaws slide in a rectangular hole in a chuck so that the transverse serrations on the inner surfaces grip the wire more firmly at the larger ends of the jaws.