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 Fatigue

AISC Fatigue

AISC Fatigue

Looking in the 13th & 14th edition of AISC, for the most part, it doesn't really matter what your yield strength is under fatigue loads. IOW, going from 36 ksi to 50 doesn't really help under most circumstances. But how about going to something like Grade 105? If you (for example) were in a situation like Case 8.5(a) (see table A-3.1, p.16.1-177 in the 13th edition)......I would think you would have a somewhat higher threshold stress than 7 ksi.

Does anyone know of a way to deal with it.....or are you stuck trying to hunt down S-N curves outside the code.


RE: AISC Fatigue

For higher grade bolts you can refer to the RCSC for more specific fatigue data. Some bolt manufacturers like Unbrako will have better more specific data also. The AISC category for 8.5 is very generic as it is applied to a wide range of threaded fasteners. Incidentally, if you pretension bolts and account for the pretensioning reduction effect on the calculated fatigue stress range, you will often have a low stress range and will not need the higher threshold.

In general using the AISC nominal stress approach, the material ultimate strength will not come into play in calculating fatigue resistance. Ultimate is used for fatigue rather than yield. You can use more detailed methods for endurance (fatigue) limits such as those found in a mechanical engineering text like Shigley. These apply to non-welded material.

Ultimate strength does not come into play at all for welded connections for the weld throat and HAZ material. Using AISC/AWS fatigue details is good in this case. If you get into more advanced methods of calculating fatigue resistance such as Effective Notch Stress or fracture mechanics then you may find the resistance is affected by the ultimate strength or other material properties. These two approaches are seldom conducive for practical engineering business/project needs.

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 – Choosing the Right Spring Loaded Connector
In today’s cost-sensitive world, designers are often driven to specify the lowest cost solution for every aspect of their designs to ensure that their solution is competitively priced and their company remains profitable. However, specifying a low-cost, low-quality connector solution can result in premature failure, considerable re-work costs and damage to reputations. Download Now
eBook – Own the Lifecycle: Sustainable Business Transformation
Increasingly, product and services companies are seeking more information and control in the operational lifecycle of their products, including service and use. Better information about the operational lifecycle, and the ability to use that information, requires more than just unstructured data flowing back from products in the field. 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