Oversized holes

[stillfan]

I have two instances where I have an oversized hole with a bolt that is 1/4" to 3/8" oversized. The first is an anchor hole, there is a 3/4" bolt in a 1 1/8" hole. If I have checked the bolt and base plate to resist the shear, fatigue is not an issue due to the low frequency of the building and there is a washer that covers the hole for uplift resistance, have I performed an analysis that will cover all aspects of an oversized hole concerns?

The second location is a purlin connection. The purlin is an axial member, so again a check for shear on the bolt and shear block on the member, as opposed to a bearing situation and fatigue analysis( once again not a concern due to the low frequency of the structure). There is no tension force on the bolt so the washer pullout is not a concern. All these parameters are meet are there any other areas of concern if the washer is not welded to the member?

 

[rscassar]

It is common to have oversized bolt holes for baseplates/foundations bolts and purlins.

 

[hokie66]

Agree with kikflip that oversized holes are common practice for column baseplates and purlins. However, if you want a column to resist a significant horizontal load at its base, a different detail is required. Site welding on plate washers is one way.

I don't like using purlins to resist axial loading, although I know some people do it.

 

[Lion06]

I agree with kikflip and hokie - These oversized holes are common for baseplates (See Table 14-2 on page 14-21 of AISC 360-05). 1 1/8" actually seems a little small for a 3/4" diameter anchor rod (I'd expect 1 5/16").

I also agree with hokie that the you need to provide a plate washer (with a standard hole) that gets field welded to the baseplate to take out the shear (if that is the load path you choose to use).

 

[wannabeSE]

Without welding plate washers, your connections might not comply with AISC 360-05. This specification allows oversized holes in slip critical connections. However, your hole size is larger than the "oversized" holes in the specification. I am curious why you do not need to check for bearing.