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Anchor Bolt hole Sizes on Top Ring and Base Ring

Anchor Bolt hole Sizes on Top Ring and Base Ring

Anchor Bolt hole Sizes on Top Ring and Base Ring

PV Elite is used to design a vertical pressure vessel. It has passed the PV elite Calculations. However, PV Elite does not perform any calculations on the topring/ basering anchor hole size (just the anchor bolt size calculation).

I was told that typically the diameter of the anchor bolt holes in the top/basering should be 0.5in more than the anchor bolt diameter. In my case, I have 1.25" anchor bolt dia for 1.75" hole through the basering and topring.

However, the site has asked for 2" hole in the base ring and top ring instead of 1.75" hole so that they can match the anchor bolt locations in the foundation at site.

Can anyone provide guidance on what calculation needs to be done to check the adequacy of the anchor bolt hole in top ring/ base ring (not the anchor bolt calculation)? Reference to manual calculation or any design manual/ code would help.


RE: Anchor Bolt hole Sizes on Top Ring and Base Ring

With such a huge clearance in the holes, you will need to detail oversize washers for this mess. The holes are 0.75" OS, I would use the largest size [ 3" x 3"?] washer that will fit the ring, and probably 3/4" thick.

RE: Anchor Bolt hole Sizes on Top Ring and Base Ring


Do you have any reference or calculation to size the washers?

RE: Anchor Bolt hole Sizes on Top Ring and Base Ring

Interesting to note that in structural works, hole sizes are normally 1/8th of an inch larger than the bolt diameters.

RE: Anchor Bolt hole Sizes on Top Ring and Base Ring

I also heard from structural guys that it shouldn't be more than 1/8" of bolt diameter (1/16" each side).
Can you double check with your structural team member?

RE: Anchor Bolt hole Sizes on Top Ring and Base Ring

Top anchor bolt hole to be bolt size + 10 mm
Bottom anchor bolt size to be bolt size + 19 mm
See PIP VEFV1110


RE: Anchor Bolt hole Sizes on Top Ring and Base Ring

As for top ring thickness, the larger the hole, the thicker the top ring. You can try to change the hole size in PV Elite and find out the required thickness to see the difference. This is because of the formula used. As for bottom ring, it won't matter much since the area cut off won't be significant compares with the entire bearing area for dead load, wind/seismic. If you cut a large hole on top ring for alignment purpose, washer shall be provided so the load can be transfer properly from nut to washer to top ring. Washer shall be welded to top ring after installation. Make the washer have a hole size = bolt dia+ 1/16" ( or 2 mm), width to be more than twice of the bolt diameter, and thick enough so it won't deform under load. Washer thickness depends on the bearing load. Your Civil engineer will be able to tell you based on the material and allowable tensional stress of the anchor bolt.

RE: Anchor Bolt hole Sizes on Top Ring and Base Ring

How can Bolt diameter meet the criterion you say - "Bottom anchor bolt size to be bolt size + 19 mm".

RE: Anchor Bolt hole Sizes on Top Ring and Base Ring

One mistake in my sentence. Sorry
Bottom anchor bolt HOLE size to be bolt size + 19 mm


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