Frequently Asked Questions

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Q: What is a field fix solution for bent or out of plumb anchor rods?

A: Care should be taken when setting anchor rods to ensure they are plumb. If the rods are not properly secured in the template, or if there is reinforcing steel interference, the rods may end up at an angle to the vertical that will not allow the base plate to fit over the rods.
 
Rods can also be damaged in the field by construction equipment and construction operations.  Anchor rod locations should be clearly flagged so that they are visible to equipment operators working in the area. 
 
Bending of high tensile class anchor rods (e.g. Property Class 8.8) is likely to result in micro-cracks that could lead to premature failures of the anchor rod [1]. Therefore repair by bending of high tensile anchor rods is not permitted.   Possible field fixes for bent or out of plumb high tensile anchor include:
  • Cut the damaged anchor rods at base level, carefully removing the surrounding concrete and install mechanical couplers and new anchor rod extensions.
  • Remove sufficient concrete that the whole of the damaged anchor rods can be removed and replaced with undamaged anchors rods.
  • Extend the baseplate, drill and grout in new anchor rods.
  • Enlarge/slot the baseplate holes and use some steel shims/additional plate washers to get full contact with the nut.
  • Reconstruction of the whole footing. 
Care is also required for bending of low tensile class (e.g. Property Class 4.6) anchor rods.  Cold bending of the threaded section may result in the formation of micro-cracks [1].  Further guidance is provided by the American Institute of Steel Construction (AISC) [2].  AISC recommend that only low tensile anchor rods be bent in the field and the bend limited to 45° or less. Rods up to about 24mm in diameter can be cold bent. Rods over 24mm can be heated up to 650 °C to make bending easier. AISC recommend that bending be done using a specialist rod bending device.  After bending, the rods should be visually inspected for cracks. If there is concern about the tensile strength of the anchor rod, the rod can be load tested.
 
Reference:
[1] Fernando, S., Specification Of Threaded Bar in Structural Applications, Australian Steel Institute, 2014
[2] Fisher, J., Kloiber, L., AISC Design Guide 1: Base Plate and Anchor Rod Design Second Edition, American Institute of Steel Construction, 2010


Anchor Rods 05/08/2016
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