Minimum bolt edge distance

[tlen22]

Hi, I'm a project engineer at a struct. firm and I was curious about a typical detail.
For this type of connection, the bolts being used are 7/8"Ø.
Reading note 4 under Table 10-9 from AISC 15th ed. it appears this edge spacing (Leh) should be 1 3/4" instead of the listed 1 1/2" (2*bolt diameter).

I'm interested in figuring out how the 1 1/2" spacing was determined and if this is something that we will have to update moving forward.
I've looked through past AISC versions and have not found distinct difference yet.
Right now my only guess is that Table J3.4 was used to determine both the Lev and Leh values which has 1 1/8" min. edge distance for 7/8"Ø bolts.

Thank you in advance!

 

[DrZoidberWoop]

Your 1.5" dimension is most likely a non-binding drafting afterthought on a standard detail, used to satisfy AISC 303 Section 3.2.3, which is fine. These types of half-baked standard details are the norm on contract drawings generated on the "owners representative for design (AISC 303 language)" of engineering.

The connection designer, working for a fabricator, will often disregard the dimensions on the standard detail entirely, in-lieu of their own preferences, which will be submitted to you for approval via calc packages and shop drawings.

 

[DanKile]

The discussion for table 10-10, which uses the conventional connection, gives a reason for the 2*bolt diameter: "Edge distance, leh, is provided as 2 times the diameter of the bolt, to match tested connections."

If you wanted to use less than 2 bolt diameters, you will need to use the extended configuration.

 

[tlen22]

@DrZoidberWoop makes sense. I kind of figured as such. Definitely something I'll bring up to my PM.
@DanKile I was going to try to find some "free time" to run some calcs to see if what we have listed makes a big difference. But I do believe it needs to be shown as 2d on the plans going forward.