×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Jobs

AISC Fatigue

AISC Fatigue

AISC Fatigue

(OP)
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.

Thanks!

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


Resources

eBook - Rethink Your PLM
A lot has changed since the 90s. You don't surf the Web using dial-up anymore, so why are you still using a legacy PLM solution that's blocking your ability to innovate? To develop and launch products today, you need a flexible, cloud-based PLM, not a solution that's stuck in the past. Download Now
White Paper - Using Virtualization for IVI and AUTOSAR Consolidation on an ECU
Current approaches used to tackle the complexities of a vehicle’s electrical and electronics (E/E) architecture are both cost prohibitive and lacking in performance. Utilizing virtualization in automotive software architecture provides a better approach. This can be achieved by encapsulating different heterogeneous automotive platforms inside virtual machines running on the same hardware. 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