Old AISC Manual - Table 7-2 Bolt Length Selection 1

[Thunderlips]

This may be a question for the older more experienced crowd. There used to be a Bolt Length Selection table (Table 7-2) in previous versions of the Steel Manual (I believe it was the Silver and/or Navy Blue versions). It made bolt length selection and determining when to use thread condition X much more straight forward. Does anyone know why this was removed? I seem to remember changes in tolerances or something like that affecting it.

If someone had a copy of a copy of a copy of this table, would it be wrong to continue to use it for determining bolt lengths and/or thread condition for bolts in shear?

 

[structSU10]

Are you saying you plan to specify the length of bolt on drawings? I thought you just note A325X or A325N to define that so the correct bolt types are purchased.

see this:

https://www.portlandbolt.com/technical/faqs/astm-a325-structural-bolt-connection-types/

 

[OldDawgNewTricks]

I guess that makes me "more experienced" then. A good reference is Charlie Carter's article "Specifying Bolt Length for High-Strength Bolts" in the 1996 2nd Quarter AISC Engineering Journal. Charlie's simple summary is that for 7/8" diameter and smaller bolts, a ply thickness of 3/8" adjacent to the nut will always exclude the threads. For 1" diameter and larger bolts, a ply thickness of 1/2" adjacent to the nut will always exclude the threads. If an ASTM F436 washer is used under the nut, the ply thicknesses can be reduced to 1/4" and 3/8" respectively. Since 1996, I have always jotted this note down in the margins of the bolt tables whenever I get a new manual.

 

[jerseyshore]

I don't know anything about that specific table but I'm pretty sure AISC has all the old manuals available for download online.

 

[Thunderlips]

This is a snip of the table I'm talking about. Note that t is the minimum thickness of ply closest to the nut required to exclude threads from the shear plane. It makes determining bolt length and checking if threads are in the shear plane very simple. My questions are does anyone know why it was removed and does anyone know if it can still be safely used?

 

[WinelandV]

I guess that makes me "more experienced" then. A good reference is Charlie Carter's article "Specifying Bolt Length for High-Strength Bolts" in the 1996 2nd Quarter AISC Engineering Journal.

I hate to point this out, but 1996 was 27 years ago. Congrats on being "more experienced"!

Please note that is a "v" (as in Violin) not a "y".

 

[JoshPlumSE]

I'm pretty sure it was just a matter of editing down the manuals so that they could be a single volume again. The information in this table, while useful, can probably be found other places as well.

Didn't Cives have a manual related to bolts for structural steel connections? My guess is a number of producers and fabricators have this table available as well.

 

[flight7]

To find out why the table was removed, go directly to the source. There is a link at this page to contact AISC: Link They have direct access to the manual's authors, and I have always found them very helpful and quick to respond.

 

[JLNJ]

How common are X-type bolts? My impression has always been that the risk of undetected field errors regarding bolt length outweighs any advantage you might gain going to threads-excluded bolts.

Where incredible precision is needed to make a connection work, especially when each one varies from the next, you are asking for trouble. I believe this is what brought down the I-55 bridge in Minneapolis - some smart connection designer was varying plate strengths and thickness to save a nickel on the connections and the subtle but critical differences were missed during fab and construction.

 

[Thunderlips]

Thanks, flight7. Going to the source was good advice. In this case, from the RCSC:

"Previous editions of this Specification treated shear planes in the thread transition length (see dimension Y in Figure C-2.2) as if the threads were excluded. Recent evaluation of this transition area and the variations permitted by ASME B18.2.6 (Swanson et al., 2020a,b) have caused the more conservative approach taken in this edition."

and:

"A more extensive table for bolt length selection based upon these rules is available (Carter, 1996; Swanson et al., 2020a)."

Look for "Dimensional Tolerances and Length Determination of High-Strength Bolts" if you're looking for the updated version of that table. Free for AISC members.