Unusual Holes Sizes in Steel-to-Steel Connections 1

[ash060]

Reviewing some drawings and the detail specifically calls out 7/8" diameter holes to be used with 3/4" bolts. Since the bolt holes are not standard and is not oversized, would it have to be slip-critical? Or is it not even allowed per the code?

 

[JoshPlumSE]

This is an interesting one. I know there has been an issue with larger diameter bolts where if the bolts and holes were manufactured within recommended tolerances, the bolts might not fit properly. But, that was address in AISC 360-2016 for bolt sizes 1" and larger. I didn't think the issue existed for 3/4" bolts.

That being said, if you have a large number of bolts in a connection, the larger size could really help make placement and fit up easier. It's certainly allowed. I'd design them as if they were oversize though. That should be conservative.

 

[ALEXZ0622]

First, 7/8" hole is allowed by AISC.

Any hole size larger than standard hole is not allowed to be used in bearing-type connections. Then slip-critical connection is required.

This happens kind of frequently, and be careful with it, because most of time, detailers don't recognize this, and consider 1/8" larger than bolt diameter is common practice. I had one project before, the detailer ignored standard hole size in SDS/2 model, and changed all hole sizes to 1/8" larger as required by galvanize guy.

If you want any quick references, please find Modern Steel Construction Magazine June & Oct 2009 Interchange. This issue has been addressed there by Larry Muir.

 

[JoelTXCive]

Good Post Alex:

I found the articles. Here are the links....

Link

https://www.aisc.org/globalassets/modern-steel/archives/2009/06/2009v06_interchange.pdf

Link

https://www.aisc.org/globalassets/modern-steel/archives/2009/10/2009v10_interchange.pdf

 

[dauwerda]

The answer to this would also depend on what "the code" is.
For example, in the US transmission industry, tapered steel poles and their connections are designed per ASCE 48. This standard actually states that the provisions given for bolted connections (bearing type) pertain to holes with diameters a maximum of 1/8" larger than the nominal bolt diameter. So a 3/4" diameter bolt with a 7/8" diameter hole would be typical when designing to this standard.