Garbage Enclosure Risk Category & Seismic

[YoungGunner]

We were asked to engineer a garbage enclosure and see if we could "halve the cost" from what a previous engineer did. This is a masonry structure, steel columns on the top, supporting a wood roof. One thing I want to verify is whether we could:
1) Justify it as a Risk Category 1 to reduce wind loads and
2) Justify it not needing to be considered for seismic loads.
I get chapter 16 of the IBC doesn't explicitly mention this kind of structure, and it does fall outside of an "agricultural storage structure", but it maintains idea of "incidental human occupancy", especially where it is not intended for any occupancy of any living creature in the first place - it just stores garbage!
Thoughts?

 

[dik]

Could you put it on a stiffened slab and use steel, with no masonry? Is there any seismic condition that accommodates a 'throw away' structure, after a quake? Just has to be safe... not salvageable.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

Risk Category 1 seems appropriate for this if it is standard domestic/light commercial garbage. Industrial or manufacturing waste may, obviously, need better protection/controls to prevent release.

I don't think you can ignore seismic, though. You can't guarantee that it will be empty when an earthquake hits (unless, it seems, you carefully measure 'critical planetary geometry'), so you have to design it to ensure it doesn't collapse while somebody is trying to recover the engagement ring that accidentally got bused from the table while the poor sap wasn't looking.

If they want to halve costs, though...just use wooden fence panels.

 

[Aesur]

Halve the cost...Remove the roof...I highly doubt going from Risk Cat 2 to 1 will make much of an effect on the design. I am not aware of any structure that can just ignore seismic, even SDC A requires consideration. Depending on the location snow may govern the design of members over wind loading. Are the walls designed to support the gate? Are the walls designed for impact loading, can bollards be used in lieu of designing the walls for said loading? Does the footing really span as if it's a grade beam or is this just how the drawing looks? Why not continuous spread footings around the perimeter? Without knowing more about the structure, size, members, reinforcing etc.. it's hard to offer any potential good solutions.

 

[YoungGunner]

"Without knowing more about the structure, size, members, reinforcing etc... it's hard to offer any potential good solutions."

I intentionally gave just enough information to validate some potential ideas I had - I'm not looking for anything more.

 

[JLNJ]

If it's in a restaurant parking lot where it could fall on somebody or some thing, then Category II for sure, despite it storing garbage.

 

[KootK]

So long as there's reinforcement in the block and reasonable steel base connections, I don't even bother designing these things. What's the worst that's going to happen to a squat, three sided building with unperforated walls? Steel superstructure shears off of the block? I have trouble even imagining that happening to a degree that would be dangerous. Of course, in my jurisdiction of residency, I'm under no obligation to submit calcs to the AHJ.

So, yeah, I'm down with whatever relaxation you can get past your AHJ reviewers. That said, I struggle to imagine what would be 50% cheaper than the base model without compromising truck bump durability.

 

[JLNJ]

You might be able to save a few bucks by not extending the footings below frost. To KootK's point - what can happen if it heaves a little? Just pour a thick-ish slab and minimally dowel the CMU to it.

 

[driftLimiter]

Unless the originally designer went bonkers overboard, its hard to imagine any amount of engineering that can reduce the cost by 50%. At the end of the day you need: a roof, columns, masonry blocks, and footings no matter which way you skin the cat. I bet whatever stupid gate they have on that makes a pretty good % of the cost of the whole thing.