GB746617A - Improvements in pre-stressed concrete construction - Google Patents

Abstract

746,617. Reinforced concrete. BOCK, F. Feb. 5, 1954 [Feb. 9, 1953 ; Sept. 29, 1953], No. 3493/54. Class 20(4). A post-tensioned reinforcement is of hair-pin or closed loop, shape, the tension being applied by a wedge member engaged between the protruding curved part of the loop and a backing plate bearing upon the concrete. When the reinforcements are closed loops E, the free ends are joined by welding, and the loops and the backing plates P are laid in a mould with the ends BS protruding beyond the plates leaving spaces A which are filled with concrete after the tensioning. The plates P have recesses Ke, which locate the ends BS in diagonal fashion, and ribs F between which wedges K are located and guided. Tangs L are bent down from the plates P and become embedded in the concrete. The wedges have flat surfaces to bear upon the plates P and curved surfaces to correspond with the curves of the ends BS. The wedges are driven by hammers, or, if the wedges of a pair are inserted from opposite directions, by a jack which forces them simultaneously towards each.other. In Fig. 5, the reinforcement is of hair-pin form, the free ends 105 each being grooved to receive a split tapered sleeve 107, with complementary grooves, the sleeve being retained by a thimble 110 which bears against the plate 102b. The sleeve, thimble and plates 102b, 102a are assembled on the reinforcement before casting the concrete, and the tension is ultimately applied by forcing home the wedge K. The grooves in the free ends 105 may be spaced and dimensioned non-uniformly.