Silo quaking in design of bins and suppport structure 1

[mte12]

Hi, just wondering what people have done for design of bin and structure, as it relates to silo quaking.

BS EN 1991-4 mentions it but says standard is limited for this.

Failures have occurred, recall reading that in one instance failure occurred after one week of operation.

Wondering what's normally done, and if there's any design guides which give steps on what to do.

 

[human909]

Are you asking because it is a currently problem on existing silos you are looking at? Or are looking at silo design and you chasing a niche scenario that isn't currently a problem?

Most silos aren't designed for quaking. Infact many aren't even designed for eccentric flow which can cause significant damage. (Manufacturers often put clauses about this aspect).
Many silos are like PEMBs. They are designed with very little safety margin above code. They also are much more likely to face ULS loads than most structures. In fact it is almost rare to see an aging silo without structural damage.

Failures have occurred, recall reading that in one instance failure occurred after one week of operation.

What sort of substance? What conditions? And was the silo designed suitably for ULS in the absence of quaking.

Wondering what's normally done.

People cross their fingers or rely on suitable experience. Also getting your material flowing properly is good, mass flow would likely improve things significantly (at a guess). Funnel flow gives the opportunity for progressive wall cave ins.

 

[mte12]

Thanks for responding human909.
This is a new design and I don't have a feel if it's a problem or not.

Was hoping for practical examples to illustrate what's done in design, understand there is difficulty in determining if quaking is an issue.

 

[human909]

Whether it is a problem or not depends on your product and your design.

Was hoping for practical examples to illustrate what's done in design, understand there is difficulty in determining if quaking is an issue.

A practical example of what is done in design? Well in practice, ~99.9% of the time, it is ignored by the designer. There is a reason why BS EN 1991-4 and most if not all other codes don't address it.

I have a decent amount of experience with silo design. Though there is certainly plenty more I could know. It is a deep field, but in practice alot of the fringe challenges and issues are not directly addressed. That said ignore too much and you could find yourself elsewhere on Eng-Tips Engineering Failures & Disasters Forum - Silo Collapse, Shoalhaven River Australia.

 

[mte12]

OK thanks human909, understand given the complexity.

Will have to figure out what to do with excitation and fatigue.

 

[human909]

If it is a "regular silo" then excitation and fatigue are normally not a big deal. Abrasive wear or corrosion is the primary end of life for most silos from my experience.

If you have aggressive hopper activators then fatigue can very much be an issue. Vibrators can lead to local fatigue cracking. Pneumatic hammers I've seen destroy hoppers in a matter of months. (The is a reason why the damn things have safety cables. It seems not a matter of IF they will fail but WHEN!

 

[mte12]

. Thanks for additional comments human909.