Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


AISC bolt pretension

AISC bolt pretension

AISC bolt pretension


I'am reading the AISC 'specification for steel structural buildings 2010' (ASD), and find chapter J.3 a bit confusing when it comes to bolt pretension and tensile strength.

So my question is:
Why is the minimum bolt pretension set to 0.7*Fu according to table J3.1 and allowable tensile strength set to Fu/omega = 0.5*Fu as in equation J3-1? It seems like the bolt pretension force is higher than the allowable tensile force. But that doesn't make sense, so I hope that someone at this forum can help me understand.


RE: AISC bolt pretension

Thanks, WillisV - I've copied out the relevant Q&A from that link:


Must the installed pretension be added to the tension or shear load when designing a bolted joint?
It is important to remember that pretension (i.e. installation tension) is always ignored when determining the design strength of a bolted joint. The initial pretension is reduced to zero (or near zero) as a bolt is loaded to failure in shear and/or tension. This effect is due to the deformations that occur prior to bolt failure. As mentioned in commentary Section 5.1 of the RCSC specification “measurements taken in laboratory tests confirm that the pretension that would be sustained if the applied load were removed is essentially zero before the bolts fails in shear (Kulak et al., 1987). Thus, the shear and tensile strengths of a bolt are not affected by the presence of an initial pretension in the bolt.” In the case of a tension connection, the initial pretension and the external tension add up to the point of separation of the connected parts. However, this increase is relatively small and is customarily ignored, as it occurs prior to bolt failure.

Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: AISC bolt pretension

Thanks WillisV.

Some of the bolted connections I'am working with is analysed in ANSYS, which include bolt pretension. So my bolt force will never get below the initial pretension.
But I guess the tensile strength for the bolts should be checked without pretension included.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper - A Guide to 3D Printing Materials
When it comes to using an FDM 3D printer effectively and efficiently, choosing the right material at the right time is essential. This 3D Printing Materials Guide will help give you and your team a basic understanding of some FDM 3D printing polymers and composites, their strengths and weaknesses, and when to use them. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close