GB711449A - Reinforced concrete constructions utilizing jointed reinforcement under tension - Google Patents

Abstract

711,449. Reinforced concrete. STRESSTEEL CORPORATION. Aug. 5, 1952, No. 19723/52. Class 20 (4) A concrete object, in one piece, is reinforced by at least one rod comprising at least two shorter rods which are joined end to end by a connector of larger diameter than the rods, bonding of the concrete with the rods and connector being prevented during the casting, and a cavity being left for housing the connector, the composite rod being suitably post-tensioned. As shown in Fig. 1, lengths of rod 12, 13, 14 are arranged in an arcuate patch and are connected by turnbuckles 15, 16 housed in boxes 20 from which the turnbuckles are spaced by springs 21, 22 or by moulded plastic blocks such as of asphalt, tar or rubber, which allow slight axial movement of the turnbuckles under the tensioning force. The rods are coated, e.g. with asphalt or tar, to prevent bonding. The tension, e.g. from 80,000 to 100,000 pounds per square inch, is applied by a hydraulic jack and is held by nuts 17, 18. In beams where the ends are not easily accessible, and in long beams it is desirable to apply the tension to the rods at points intermediate the ends. In this case, Fig. 3, it is necessary to have the boxes 30 open for access, the jack 33 being designed to press nuts 32 on to the rod ends towards one another. The right and left-handed threads on the ends of the rods are interrupted in breech-block fashion, the threads in the turnbuckle 34 being correspondingly interrupted. When the jack is applied, the turnbuckle is turned to permit the rod ends to slide therein, the turnbuckle being turned to engage the threads and hold the tension before the jack is released. The nuts are then screwed against the turnbuckle to lock it, and the cavity is filled with grout or other protective material. Alternatively, the ends of the rods are not screwthreaded, the jack having clamping jaws which grip the rod ends which are joined by a clamp to enable the jack to be released. As shown in Fig. 6, two separately pre-stressed beams 50, 51 are arranged in line to permit the pre-tensioned reinforcements to be connected by a breech-block threaded turnbuckle 57. The nuts 55 are shaped for engagement by a jack so that the reinforcements may be further tensioned without relieving the original pre-stress in the beams, the increased tension being held by the turnbuckle. Split washers 58 are removed when relieved of the pressure of the nut 55 which may, when the jack is removed, be screwed against the turnbuckle. A pre-stressed beam may have its reinforcement joined to reinforcement projecting horizontally from a vertical structural member, and additional pre-stress applied to the beam in the same manner as is described with reference to Fig. 6.