Releasable coupling device for use with reinforcing tendons and method of using the same

Abstract

A coupling device for attaching a protruding tendon disposed in a concrete structure to an extension strand comprises a barrel having a first end and a second end, a first conical bore disposed adjacent the first end having a first pair of wedges and sized to receive and grip the protruding tendon, a second conical bore disposed adjacent the second end and having a second pair of wedges and sized to receive and grip the extension strand, and a release bushing adapted for placement adjacent the first end of the barrel and having an aperture sized to receive the protruding tendon. The release bushing includes a contact surface positioned to contact the first pair of wedges and arranged to shift the first pair of wedges to a disengaged position in response to shifting the first end of the barrel toward the release bushing.

1 . A coupling device for attaching a protruding tendon disposed in a concrete structure to an extension strand, the coupling device comprising: 
 a barrel having a first end and a second end;    a first conical bore disposed adjacent the first end having a first pair of wedges, the first conical bore sized to receive the protruding tendon such that the protruding tendon is grippable by the first pair of wedges when the first pair of edges are shifted to an engaged position;    a second conical bore disposed adjacent the second end and having a second pair of wedges, the second conical bore sized to receive the extension strand such that the extension strand is grippable by the second pair of wedges when the second pair of wedges are shifted to an engaged position; and    a release bushing, the release bushing adapted for placement adjacent the first end of the barrel and having an aperture sized to receive the protruding tendon, the release bushing including a contact surface positioned to contact the first pair of wedges, the contact surface of the release bushing arranged to shift the first pair of wedges to a disengaged position in response to shifting the first end of the barrel toward the release bushing.    
     
     
         2 . The coupling device of  claim 1 , wherein the barrel is separable into a first part and a second part, and wherein the second part includes an internal spring positioned to bias the second pair of wedges in an outward direction.  
     
     
         3 . The coupling device of  claim 2 , wherein each of the first part and the second part includes a threaded internal bore, and including a threaded barrel for joining the first part to the second part.  
     
     
         4 . The coupling device of  claim 3 , wherein the internal spring engages the threaded barrel and the second pair of wedges.  
     
     
         5 . The coupling device of  claim 1 , wherein the second pair of wedges are spring biased in an outward direction, and further wherein the second pair of wedges are arranged to shift in an inward direction in response to insertion of the extension strand in the second conical bore.  
     
     
         6 . The coupling device of  claim 1 , wherein the first conical bore and the first pair of wedges are sized to expose a tip of the first pair of wedges.  
     
     
         7 . The coupling device of  claim 1 , wherein the first conical bore and the first pair of wedges are sized to permit a tip of the first pair of wedges to extend out of the first conical bore when the first pair of wedges are in an engaged position.  
     
     
         8 . The coupling device of  claim 7 , wherein the release bushing includes an outer sidewall surrounding the contact surface, the contact surface depressed relative to the outer sidewall.  
     
     
         9 . The coupling device of  claim 8 , wherein the outer sidewall includes an edge sized to engage a corresponding edge on the first end of the barrel when the release bushing is brought into contact with the barrel.  
     
     
         10 . A coupling device for operatively connecting a protruding tendon disposed in a concrete structure to an extension strand, the coupling device comprising: 
 a main body having a first end and a second end;    a first bore disposed adjacent the first end and arranged to receive the protruding tendon;    a first pair of wedges disposed within the main body adjacent the first end, the first pair of wedges shiftable between a disengaged position in which the protruding tendon is moveable within the first bore and an engaged position in which the protruding tendon is secured within the first bore;    a second bore disposed adjacent the second end and arranged to receive the extension strand;    a second pair of wedges disposed within the main body adjacent the second end, the second pair of wedges shiftable between a disengaged position in which the extension strand is moveable within the second bore and an engaged position in which the extension strand is secured within the second bore; and    a release bushing, the release bushing adapted for placement adjacent the first end of the main body and having an aperture sized to receive the protruding tendon, the release bushing positioned to contact the first pair of wedges, the release bushing arranged to shift the first pair of wedges to the disengaged position in response to shifting the main body toward the release bushing.    
     
     
         11 . The coupling device of  claim 10 , wherein the first bore is aligned with the second bore.  
     
     
         12 . The coupling device of  claim 10 , wherein the second pair of wedges are biased toward the engaged position, the second pair of wedges arranged to shift toward the disengaged position in response to inserting the extension strand into the second bore.  
     
     
         13 . The coupling device of  claim 12 , wherein the main body is separable into a first part and a second part, and wherein the second part including the second bore, the second part further including an internal spring positioned to bias the second pair of wedges toward the engaged position, the spring bearing against a plug threaded into the first bore and the second bore.  
     
     
         14 . The coupling device of  claim 10 , wherein the first pair of wedges include a tip, the first bore and the first pair of wedges sized to expose the tip when the first pair of wedges are in the engaged position.  
     
     
         15 . The coupling device of  claim 10 , wherein the first bore and the first pair of wedges are sized to position the first pair of wedges for contact with the release bushing when the first pair of wedges are in the engaged position.  
     
     
         16 . The coupling device of  claim 15 , wherein the first bore is conical, the first pair of wedges sized to protrude from the first bore when the first pair of wedges are in the engaged position, and wherein the release bushing includes an outer sidewall surrounding a depressed contact surface.  
     
     
         17 . The coupling device of  claim 16 , wherein the outer sidewall defines a contact surface positioned to engage a first end of the body when the release bushing is brought into contact with the body.  
     
     
         18 . A coupling device for operatively connecting a protruding tendon disposed in a concrete structure to an extension strand, the coupling device comprising: 
 a main body having a first end and a second end;    first and second oppositely facing conical bores, the first bore arranged to receive the protruding tendon;    a first pair of wedges disposed within the first bore and shiftable between a disengaged position in which the protruding tendon is axially moveable within the first bore and an engaged position in which the protruding tendon is secured within the first bore;    a second pair of wedges disposed within the second bore and shiftable between a disengaged position in which the second pair of wedges are positioned to permit an extension strand to move axially within the second bore and an engaged position in which the second pair of wedges are positioned to grip an extension strand disposed within the second bore; and    a release bushing, the release bushing adapted for placement adjacent the first bore and having an aperture sized to receive the protruding tendon, the release bushing including a first surface positioned to contact the first pair of wedges when the release bushing and the main body are brought toward each other to thereby shift the first pair of wedges to the disengaged position.    
     
     
         19 . The coupling device of  claim 18 , wherein the first bore is axially aligned with the second bore, and including a spring disposed adjacent the second pair of wedges and arranged to bias the second pair of wedges toward the engaged position, the spring arranged to permit the second pair of wedges to shift toward the disengaged position in response to insertion of the extension strand into the second bore.  
     
     
         20 . The coupling device of  claim 19 , wherein the main body includes a first part and a second part joined by a threaded plug, the spring positioned to bear against the threaded plug.  
     
     
         21 . The coupling device of  claim 20 , wherein the first pair of wedges include a tip sized to protrude from the first bore when the first pair of wedges are in the engaged position, and wherein the first surface of the release bushing is defined by a depressed central portion surrounding the aperture.  
     
     
         22 . The coupling device of  claim 21 , wherein the release bushing includes an outer sidewall surrounding the depressed central portion.  
     
     
         23 . A method of releasing the tension on a tendon protruding from a concrete structure comprising the steps of: 
 providing a chair sized to fit over a wedge plate;    positioning the chair over the wedge plate;    providing a coupling device having first and second pairs of oppositely facing wedges;    providing a release bushing over the protruding tendon and positioned to engage the first pair of wedges;    securing the first pair of wedges to the protruding tendon;    positioned an extension strand in the second pair of wedges;    using a tensioning ram to grasp the extension strand and to apply a greater tension to the tendon to thereby displace the tendon away from a first position in a first direction;    removing an original pair of wedges from adjacent the displaced tendon;    using the tensioning ram to displace the tendon in a second direction opposite the first direction to a second position; and    displacing the tendon in the second direction a distance sufficient to cause the release bushing to shift the first pair of wedges out of engagement with the protruding tendon.