Apparatus and method for anchoring post-tensioning tendons in prestressed structures

Claim 1

IN A PRESTRESSED STRUCTURE, SAID STRUCTURE HAVING A PLURALITY OF TENDONS UNDER POST TENSIONING TENSION PASSING THERETHROUGH, SOCKET MEANS DISPOSED IN SAID STRUCTURE TO FORM A RECESS AT ONE LOCATION THEREIN, THE TENDONS EXTENDING THROUGH SAID SOCKET MEANS, A FORCE TRANSMITTING PLUG FOR COUPLING THE TENDONS TO THE STRUCTURE, SAID FORCE TRANSMITTING PLUG COMPRISING GROUT FORMED AND SET ABOUT PORTIONS OF SAID TENDONS EXTENDING THROUGH SAID SOCKET MEANS SO THAT A PORTION OF SAID PLUG IS IN FORCE COUPLING RELATION TO SAID STRUCTURE, SAID GROUT PLUG HAVING A DIMENSION ALONG THE TENDONS SUFFICIENT TO FORM A PERMANENT BOND THERETO, SAID PLUG SERVING TO TRANSMIT TENSIONING FORCES FROM THE TENDONS TO THE STRUCTURE IN SUCH FASHION THAT PORTIONS OF THE TENDONS CLOSER TO THE STRUCTURE ARE MORE SECURELY BONDED WITHOUT ANY SLIPPAGE IN FORCE COUPLING RELATION TO THE GROUT PLUG THAN ARE PORTIONS OF THE TENDONS FARTHER AWAY FROM THE STRUCTURE, SAID SOCKET MEANS SERVING TO RADIALLY CONFINE SAID GROUT PLUG SO THAT WHEN SAID PLUG IS COMPRESSED BY SAID TENDONS, THE BOND BETWEEN THE TENDONS AND THE PLUG IS INCREASED DUE TO RADIAL EXPANSION OF THE TENDONS AND THE PLUG AGAINST THE RADIALLY CONFINING WALL OF SAID SOCKET MEANS, SAID TENDONS INCLUDING UNTENSIONED PORTIONS EXTENDING BEYOND THE GROUT PLUG AND AWAY FROM THE STRUCTURE, AND MEANS SECURING SAID UNTENSIONED PORTIONS EXTENDING BEYOND THE PLUG SO THAT UPON FAILURE OF THE BOND BETWEEN SAID PLUG AND TENDONS, THE TENDONS ARE STILL RETAINED BY SAID LAST NAMED MEANS.