Specifying Pretensioned Bolts 1

[Boiler106]

What is the proper method of specifying pretensioned bolts in, say, a single detail?

I know of A325TC bolts, but that limits the pretensioning to tension control bolts.

This is silly, but does " 3/4in dia A325 Pretensioned bolts" work as a callout or is there a more conventional way?

 

[WARose]

I normally say something like "8 [or whatever number of] bolts, 3/4" dia. A325 SC (CLASS A)"

EDIT: By the way, it's interesting you ask this question because I had the same one on here myself a few months back (and didn't get a reply). I use it so infrequently.....I wonder if I do it right myself.

 

[phamENG]

Take a look at the RCSC (specifically page 16.2-26 in the 14th edition of the steel manual) at Table 4.1. They provide Joint Type designations for various conditions - ST for snug tight, PT for pretensions for reasons other than slip resistance, and SC for slip critical. So I'd say WARose is spot on. Section 1.4 outlines the minimum information required on the drawings from the EOR - ASTM designation, Joint Type, Class of slip resistance if SC, and load level (strength vs. service) of the slip check. As long as you find a clear and unambiguous way of relaying that information, you should be fine. Just review the shop drawings closely - the fabricator's detailer will let you know if you did it "wrong."

 

[JAE]

If your plans/notes reference AISC 360, which in turn references the RCSC Specification for Structural Joints Using High Strength Bolts, then your simple notes would be something like this:

Snug Tightened: PROVIDE (3) 3/4" DIA. ASTM A325N BOLTS

Pretensioned: PROVIDE (3) 3/4" DIA. ASTM A325N BOLTS (PRETENSIONED)

Slip-Critical: PROVIDE (3) 3/4" DIA. A325N BOLTS (SLIP CRITICAL CLASS A)

X type bolts or N type bolts are, for us, usually dealt with in the general notes as well (we try to use all of one kind on each project to avoid on-site confusion and mix-ups).
We also state in our notes that all bolted connections are snug tight unless otherwise specifically noted on the details.

There is a difference between Pre-tensioned and slip critical as the former doesn't require requirements for faying surfaces - see the RCSC specification.

 

[dik]

Hasn't the ASTM A325 been replaced with:

-BOLT SPECIFICATIONS OF ASTM F3125, GRADE A325 HAS BEEN USED AND NOT ASTM A325.

Just curious...

Dik

 

[BridgeSmith]

You beat me to it, dik. Yes, the ASTM spec is now F3125, and Grade A325 is one of several grades under that specification. They kept the A325 (and A490, etc.) designation so that those didn't know/didn't care could still get away with calling out 'A325 bolts' and get what they were expecting.

Rod Smith, P.E., The artist formerly known as HotRod10