topic AISC Allowable stress Increase in Robot Structural Analysis Forum

AISC Allowable stress Increase

stef.niemczyk — Mon, 15 Oct 2018 09:30:47 GMT

Dear Artur,

I seem to be having a problem with the 33% Allowable Stress Increase per AISC 9th Edition. Ticking the option doesn't seem to change anything if we check the calculation note post calculation.

I have attached an excel sheet showing the calculaiton results for a same beam. the first one on the left is without secondary stresses and no stress increase. The second on the right is with secondary stresses and with stress increase.

In both cases, the allowable Fa and Fv are the same.

can you check on that and let me know if it's something that I'm not getting right or issue with code check?

thanks

stephane

Re: AISC Allowable stress Increase

Artur.Kosakowski — Mon, 15 Oct 2018 09:32:37 GMT

Hi @stef.niemczyk

Could you attach the corresponding Robot model too?

Re: AISC Allowable stress Increase

stef.niemczyk — Mon, 15 Oct 2018 09:51:19 GMT

Artur

Sure, See Attached. The structure in question is an Offshore Drilling Derrick and we verify the compliance to AISC 9th edition against a set of combination of given loads (Dead, Live and Wind).

The beam I was referring to in the excel file i sent earlier was Beam 266, so you can link to something.

Hope this helps.

best regards

Stephane

Re: AISC Allowable stress Increase

stef.niemczyk — Tue, 23 Oct 2018 07:26:17 GMT

Hi Artur

Gentle follow up on this topic please.

Thanks and regards

Stephane

Re: AISC Allowable stress Increase

Artur.Kosakowski — Tue, 23 Oct 2018 08:39:51 GMT

Hi @stef.niemczyk

I'm keeping it on my to do list it has to wait till I'm able to meet with the development team. I'm sorry for not being able to provide you with the answer yet but I will update this topic the moment I have any new information.

Re: AISC Allowable stress Increase

Artur.Kosakowski — Mon, 29 Oct 2018 15:28:43 GMT

Hi @stef.niemczyk

The 33% of allowable stress increase applies to wind and seismic loads only

If for bar 266 which you focused on you select e.g. 3019 combination which include a wind load case you can see that there is a difference when you have this option switched off (left) on on (right):

When you design against a combination with neither wind nor seismic loads the results are the same (with no stress limit increased) for both sensations (e.g. for )

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