A prestressed concrete tensioning system for a tensioning tendon comprising:
- an anchor seat embedding in one end of a prestressed concrete beam and comprising a hollow hemisphere body having a plurality of screw holes formed spaced apart around a rim and a tapered extension including a tapered central bore and a corrugated outer periphery axially extending outward from a bottom thereof, a hollow hemisphere cover engaging said hollow hemisphere body by means of screws to define a spherical receiving space therein, said cover having a plurality of screw holes in a rim thereof made in registry with the screw holes of said hollow hemisphere body and a circular recess including an aperture therein centrally formed in a bottom thereof, a pair of identical hemisphere members for configuring a spherical body movably disposing into said spherical receiving space and biasing by a spring means, said hemisphere members each having a semi-conical groove for configuration of a tapered central bore thereinbetween formed along a radial line of a flat portion thereof, and a pair of semi-conical means for configuring a tapered body slidably disposing into said tapered central bore, said semi-conical means each having a semi-cylindrical groove centrally formed along the axis including a plurality of inverse ratchets formed therein for gripping said tendon therebetween;
- a prestressed tensioning device comprising:
- an adaptor having a hollow cylindrical body, a hemispherical concave formed in a fore end and a threaded inner periphery in a rear end thereof;
- a hollow cylindrical housing engaging said adaptor having a central bore through the body, a neck axially extending outward from a fore end including a threaded outer periphery which is made in registry with the threaded inner periphery of said adaptor, a hydraulic fluid chamber in a rear portion communicating an external hydraulic source via a pair of first and second conduits in a peripheral wall of said housing;
- a piston member slidably disposing into the central bore of said housing having a cylinder body, an annular flange extending outward from an outer periphery, a stepped extension axially extending outward from a fore end including peripheral thread adjacent a free end thereof, a central bore axially extending through the body, a conduit axially extending along a peripheral wall and through the body thereof and a threaded circular recess centrally formed in a bottom for engaging a cylindrical stopper therein which has a threaded outer periphery and a transverse slot in outward end;
- an annular ring slidably disposing on the stepped extension of said piston member having an annular flange extending inward from a medial inner periphery and a plurality of screw holes formed spaced apart around a fore rim thereof;
- a grip assembly engaging the stepped extension of said piston member having a hollow cylindrical body of U-shaped section, a central bore aligning with the central bore of said piston member, a threaded inner periphery made in registry with the threaded outer periphery of said stepped extension and a dovetail slot transversely extending across the bottom along a radial line thereof;
- a pair of grip jaws slidably engaging said grip assembly each having a wedged outward surface, a flat inward surface, a dovetail tang projecting outward from a bottom made in registry with the dovetail slot of said grip assembly, a central groove axially extending through the flat inward surface and a pair of recesses formed adjacent the central groove for engaging in a pair of spring rods respectively;
- a grip housing engaging said annular ring by means of screws, having a plurality of screw holes axially formed through a peripheral wall and made in registry with the screw holes of said annular ring and a cylindrical space abutting a tapered space formed inside the body thereof for receiving said grip jaws and said grip assembly therein;
- whereby said prestressed tensioning device in cooperation with said anchor seat provide sufficient tensioning force to complete a prestressed tensioning process for a prestressed concrete beam.