Short Anchor rods (again)
Short Anchor rods (again)
(OP)
I know there are a few threads on short anchor rods but I have a slightly different situation. The anchor bolts are 'short' but there is still ~2.5 threads available above the top of the nut. The EOR is stating that we need to core drill out the existing anchor rods and install post installed anchors. There is information on using couplers, anchor welding, ext but the EOR is stating that the 'rule of thumb' is a minimum of 3 exposed threads above the nut minimum. AISC DG1 states you can get away with a minimum of 50% of thread engagement as long as you can prove through analysis that the engage threads resists the applied load. In my case, I have 100% thread engagement but admittedly the projection is less than I would typically specify. The column weight is less than 10 kips with a little bit of shear and moment.
The EOR's fix seems like A LOT of work over 1/2 a thread less than his rule of thumb and extending the anchor by welding or coupling doesn't make sense given there is full nut engagement. Thoughts?
The EOR's fix seems like A LOT of work over 1/2 a thread less than his rule of thumb and extending the anchor by welding or coupling doesn't make sense given there is full nut engagement. Thoughts?






RE: Short Anchor rods (again)
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Short Anchor rods (again)
RE: Short Anchor rods (again)
RE: Short Anchor rods (again)
Sandman: Good find in the AISC manual. Secondly, I havent even started using the 14th edition let alone the 15th!
RE: Short Anchor rods (again)
Dik
RE: Short Anchor rods (again)
There is a nut, which I can't seem to find right now, that extends below the baseplate. They are specifically made for the situation of insufficient anchor rod projection you are describing. If I remember right they are tested to prove they can develop the strength of the rod. It'd be hard for the EOR to argue against their use. You'd have to enlarge baseplate hole slightly.
EDIT: These are what I'm talking about: https://www.canam-construction.com/en/construction...
RE: Short Anchor rods (again)
The product that Rabbit12 is referring to is Elocone Nuts by Canam. They work great, but they're not free.
Is there a requirement in the contract documents for this extension? An engineers rule of thumb isn't a project requirement unless its in there.
RE: Short Anchor rods (again)
From Bolt Science:
In summary the full height of the nut is to be used if you are to avoid thread stripping - that is - ensure that the thread protrudes through the nut. Also use a standard height nut as this is designed so that the bolt will break before the threads start to strip.
http://www.boltscience.com/pages/shortbolting.htm
and from Portland Bolt:
RCSC (Research Council for Structural Connections) Specification for Structural Joints Using ASTM A325 or A490 Bolts 2.3.2. Geometry
“Heavy-hex structural bolt dimensions shall meet the requirements of ANSI/ASME B18.2.6. The bolt length used shall be such that the end of the bolt extends beyond or is at least flush with the outer face of the nut when properly installed.”
http://www.portlandbolt.com/technical/faqs/recomme...
Both sites have added info...
Dik
RE: Short Anchor rods (again)