Post-Tensioned Concrete Reinforcement Anchor Assembly With Radiused Tooth Tips

Abstract

A wedge for a concrete post-tension reinforcement anchorage system is shaped such that the compressive force on the tendon after tensioning of the anchorage system is substantially evenly distributed over a length of the outer surface of the tendon that is engaged by the internal surface of the wedge. The external surface of the wedge may have a first section with a first taper angle and a second section with a second taper angle, the second taper angle being larger than the first taper angle. The internal surface of the wedge may have a first section with a first taper angle and a second section with a second taper angle, the second taper angle being greater than the first taper angle. An anchor with a bore with two taper angles and tooth profiles of threading patterns on the internal surface of the wedge are also disclosed.

1 . A post tensioned concrete reinforcement anchor assembly, comprising:
 a cable tendon formed of steel wires wound in a helical pattern with an outer helical shape around a centrally positioned steel wire;   an anchor having a flange with a front surface and a rear surface, the anchor having at least one wedge receiving bore, the wedge receiving bore having a tapered interior surface; and   a segmented wedge having an external surface configured to engage the tapered interior surface of the wedge receiving bore of the anchor and contract as the wedge is drawn into the wedge receiving bore, the wedge having an internal surface configured to contract as the wedge is drawn into the wedge receiving bore and engage an outer surface of the tendon, the internal surface including a thread pattern having a plurality of teeth with a tooth tip that has a radius greater than zero that reduces stress concentrations exerted on the tendon by the tooth tip relative to tooth tips with a radius of zero.   
     
     
         2 . An assembly as claimed in  claim 1 , wherein the radius on the tips of the teeth is nominally 0.005 inches. 
     
     
         3 . An assembly as claimed in  claim 2 , wherein the thread pattern includes a flat valley section between each pair of adjacent teeth in the thread pattern. 
     
     
         4 . An assembly as claimed in  claim 3 , wherein the flat valley sections are at a consistent minor diameter. 
     
     
         5 . In a post tensioned concrete reinforcement anchor assembly that grips a cable tendon formed of steel wires wound in a helical pattern with an outer helical shape around a centrally positioned steel wire, the assembly including an anchor having a flange with a front surface and a rear surface, the anchor having at least one wedge receiving bore, the wedge receiving bore having a tapered interior surface, and a segmented wedge having an external surface configured to engage the tapered interior surface of the wedge receiving bore of the anchor and contract as the wedge is drawn into the wedge receiving bore, the wedge having an internal surface configured to contract as the wedge is drawn into the wedge receiving bore and engage an outer surface of the tendon, the internal surface including a thread pattern having a plurality of teeth with a tooth tip, the improvement wherein each tooth tip has a radius greater than zero that reduces stress concentrations exerted on the tendon by the tooth tip relative to tooth tips with a radius of zero. 
     
     
         6 . The improvement as claimed in  claim 5 , wherein the radius on the tips of the teeth is nominally 0.005 inches.