Pretensioned prestressing of concrete members - uses axial compression on temporarily embedded bar to effect tensioning of stressing wires

摘要

The pre-tensioning system induces beneficial compressive stresses in a concrete structural member, effecting the axial compression of a re-usable bar (5) in order to tension the tendons. The bar (5) and the tendons (1) extend between fixed (2) and movable (3) anchorages, bar compression being effected by screw jacking at the latter (3). The bar may be sheathed (7) to facilitate withdrawal once the concrete has matured. At anchorage (2), a spherically segmental bar end (23) abuts a bearing plate (22) of reciprocal form. A bolt (6) passes through a nut (62) at anchorage, having a hexagonal head (64) for rotation by a two way jack, and bearing on the bar end via a centring stud (63).