Nonstructural component Ch 13 or Non building structure Ch 15 ASCE 7 (AHU) 2

[joengineering]

Fellow Engineers,

I came across an AHU I have to design the anchorage for. I am almost sure that this is a non structural component and that I have to use Ch 13 in ASCE 7 (seismic coefficents are clearly stated for "air handlers" in Ch 13 table), but this AHU is not inside a building or attached to the building, it is sitting outside on SOG. Reading CH 13, is states that any nonstructural component attached to a building is designed with Ch 13. Also, Ch 15, refers me back to Ch 13 for any architectural, mechanical, and electrical components supported by nonbuilding structures. Should I use Ch 13 requirements even though the AHU is not attached or supported by a nonbuilding structure or building? Or is Ch 15 what I have to use even though an AHU does not really fall into a nonbuilding structure not similar to building category?

I hope you guys could help me figure out which requirements I need to obey, Ch 13 or Ch 15.

Thank You

JO

 

[JedClampett]

I'd use 13. It seems that 15 is more for structures (racks, air supported structures, etc.)and 13 is for equipment. Or pick the one that gives you the highest load and use that.

 

[PMR06]

Here's an article from Structure Magazine that talks about Chapter 13 vs 15. The flow chart may help.

http://www.structurearchives.org/article.aspx?articleID=1405

 

[joengineering]

Thank for the suggestions,

jedclampett, yes I usually pick the highest load and use that, it is conservative. But it would be nice to know which one it is exactly.

prm06, that flow chart takes me to ch 15, just because it is not attached/supported by another structure.

This is so confusing :/

 

[JStephen]

Of the two, it looks like Ch. 15 would be the one applicable.

It is not actually all that clear if ASCE 7 would be applicable to it in the first place. Per IBC, a structure is "that which is built or constructed", which could be construed to include just about every physical object, but the definition is usually construed in a more narrow sense; otherwise, we'd all be analyzing our coffee cups and staplers for seismic stability.

 

[joengineering]

Stephen,

Are you saying it does not even need to be check for seismic? But this is a 20'x20'x12'High AHU.

JO

 

[JStephen]

I'm saying it's not clear where the cutoff is, if there is one, between "structures" and "other stuff" in the codes.
There was another thread about anchors on a rectangular tank. That tank is about the size of a semi.
So why does the rectangular tank require seismic design but a semi parked next to it doesn't?
But for a 20'x20'x12' item, I'd include it under Chapter 15.

 

[joengineering]

jstephen,

Thanks for the advice

JO

 

[joengineering]

I guess at the end, if you are unsure, just do both ch 13 and ch 15 requirements. Whatever the worst loading is, use that.

 

[wannabeSE]

Whether it is right or wrong, chapter 12 is often used for outdoor equipment anchorage (switchgear, generators, etcetera). I don't think the earthquake cares if the equipment is on a slab-on-grade inside a building or slab-on-grade outside the building, the forces will be similar (the same).

 

[joengineering]

WannabeSE,

You mean ch 13?

JO

 

[Bendog01]

Here is another reference that may help. It's from a webinar by ASCE on Nonbuilding structures and components. See slides 28 thru 30.

 

[joengineering]

Bendog01,

Thanks.

 

[wannabeSE]

Joe
Sorry - I should proof read before submitting. I meant chapter 13 - non-structural components.

 

[joengineering]

WannabeSE,

Yes I agree with you. I feel like ch 13 is correct. But they should really add that not all equpment need to be attached/supported by a structure', it is a bit confussing.

JO

 

[Once20036]

I recently looked at a problem in sdc D where we were adding several equipment access platforms to an existing building.
It seemed strange that platforms placed on an elevated level fell into chapter 13, but the 25% weight rule, but that platforms on the ground floor fell into chapter 15.

I designed all of them per chapter 13.

 

[joengineering]

Once20036,

Thanks for the feedback. I guess in cases like these we just have to use our engineering judgement.