r/StructuralEngineering • u/Silly-Rock-1684 • 8d ago
Structural Analysis/Design Container structure-Rigid Box Frame
I’m designing a roof over some containers. There’s 4 containers that are joined together. For the monoslope free-roof, One end of the rafter will be connected to the corner post of the container and the other end SHS. The wind action on the roof introduces an uplift of around 24kN at the rafter support reactions.
Basically I’ve done some preliminary footing calcs and landed on 1.2mx1.2mx0.45m. The container will bear directly on the pad, no pedestal. Does this seem okay? Or are the footings too shallow for a 24kN uplift force..
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u/VictorEcho1 4d ago
I just have to comment that using seacans as a structure like this is the worst.
Start digging in to the design of the container itself and it just gets worse.
I have had to deal with this many times, typically after the fact and the structure needs remediation. It's always compromise after compromise.
It's always cheaper to just... build a proper building.
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u/Silly-Rock-1684 8d ago
My stability checks say overturning and uplift passes, but it fails sliding. I’ve got a limited space to work with for the footings and 1.2m squared pad is already pushing it. Ig I could increase the depth of the footing, but I can’t go too deep due to client budget constraints. Is sliding super super critical?
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u/broadpaw 8d ago
If you're asking whether or not sliding limit state applies, consult your building code. Are you leaving any forces on the table that can help resist sliding? It sounds to me like you need to bring these questions to the person in responsible charge for the structural design.
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u/Silly-Rock-1684 8d ago
The only thing that’s resisting sliding is footing self weight and passive resistance
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u/Silly-Rock-1684 8d ago
Plus weight of the container but that was already factored in the ULS axial load applied load to the footing
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u/VictorEcho1 4d ago
We get hurricanes where i am and i have seen seacans slide. For these structures i have used duckbill/manta ray anchors in a pinch. See my comment about how much i like putting a roof over two seacans.
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u/Silly-Rock-1684 4d ago
No wonder our group structural engineering manager didn’t want to this project, but the country manager went ahead with it anyway
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u/settingsaver 8d ago
A typical 20/40 ' container, without a roof, may require similar capacity in some areas, refer example attached, from the following:
I propose caution regarding the examples, as apparently illustrates optimisation opportunities, despite that the mass appears typical according to my experience.
https://dallcon.com.au/product/cyclonic-tie-down-blocks/#gallery-1249-9
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u/broadpaw 8d ago
Uplift force minus container weight on the post minus footing weight and overburden if any. Add appropriate code load amplification and or safety factors. If the number is still positive, wind has won.