A Fatigue Question?

[jascia1919]

If I know for sure a steel member and its connection is under compression. Eg. Steel Arch splice full pen weld.

Live load will only change the magnitude of compression but not the sign.

Do I still need to check the fatigue as per AASHTO or other codes.

It is a real question I have from my job. I am thinking theoretically I should check. But actually it won't control.

Thanks.

 

[MA_PE]

If I know for sure a steel member and its connection is under compression. Eg. Steel Arch splice full pen weld.
Live load will only change the magnitude of compression but not the sign.

Do I still need to check the fatigue as per AASHTO or other codes.

It is a real question I have from my job. I am thinking theoretically I should check. But actually it won't control.

Thanks.

yes. I need to revisit the code to get the numbers but I recall there that fatigue limits the stress range due to live load regardless if it reverses sign or not.

 

[awesomepogi]

Fatigue involves stress range & not just stress reversal per se. Just get the absolute value of the difference between max & min stresses & compare that range to the allowable.

If you're using SN curves, the allowable stress range is specified for corresponding fatigue stress application vs. no. of cycles.

Appendix 3 of AISC 13th ed. deals with fatigue design