Bar Post-Tensioning System

Stressing and Grouting


 

DYWIDAG Threadbars are stressed using compact lightweight hydraulic jacks. In most cases handled by one man, the jack fits over a pull rod designed to thread over the THREADBAR ® protruding from the anchor nut. The jack nose contains a socket wrench and ratchet device which allow the nut to be tightened as the THREADBAR ® elongates.

1-3/4" and 2-1/2" bars utilize specially equipped center-hole stressing jacks. The magnitude of the prestressing force applied is monitored by reading the hydraulic gauge pressure and by measuring the THREADBAR ® elongation. The elongation can be measured directly by noting the change in threadbar protusion.

 


Jack Capacity Kips 67 160 220 330* 630*
  kN 267 712 979 1,500 2,800
Bar size in 5/8 1,11/4 11/4,13/8 13/4 21/2
  mm 15 26, 32 32, 36 46 65
a** in 73/4 81/2 11 N/A N/A
  mm 197 216 279    
b in 31/4 4 6 6 7
  mm 83 102 152 145 180
Min. c in 24 26 30 36 43
  mm 610 660 762 900 1,070
Weight lbs 50 80 110 334* 500
  Kg 23 36 50 152 227
*) this system should have a mechanical means of lifting and moving.
**) Special nose extensions for deep stressing pockets are available on request.

Note: Detailed operating and safety instructions
are provided with all stressing and grouting units.
Read and understand these instructions before
operating equipment.


Grouting

Grouting completes the installation process for post-tensioned concrete construction.The grout is important in protecting the steel from corrosion and contributes significantly to the ultimate strength of the structure. After mixing, the grout is injected into a low point vent until consistent material is exhausted at the terminating or anchorage vent. An admixture may be used to control expansion and pumpability.