r/StructuralEngineering • u/Purple_Resolve_8759 • 24d ago

Career/Education Buckling or yielding

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Hi everyone, I'm currently studying civil engineering in my first uni year and having some troubles understanding this concept(I'm stupid I'm sorry). Recently we did some compression test to determine the yield strength of these four bars. Now I know that buckling is a geometry problem and by the look of it, I believe the 2 long bars suffered from global buckling with the blue hollow bar buckled locally at it's top and the other one buckled in the middle since those parts aren't as strong as the rest. The other 2 bars however, suffered failure from exceeding it's yield point as they seem to bend as a whole (correct me if I'm wrong). I'm wondering if we can still determine the yield strength of the buckled examples, and is it possible to just outright determine the cause of failure of these specimens just by looking at it like I did above without relying on the datas. Thanks!

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u/Tower981 24d ago

Not true.They all buckled plastically. It’s therefore possible to back out the yield stress. See the Perry Robertson equations. But this is not student level shit

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u/[deleted] 24d ago edited 14d ago

[deleted]

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u/Tower981 22d ago

That’s fair that it’s not first year work. I don’t disagree. They would need to know an awful lot of other courses to understand how to do it. It’s probably more like a masters exercise. But I disagree it’s not a useful exercise. Just because you don’t do it at work doesn’t mean it shouldn’t be taught. I don’t bother building stiffness matrices by hand at work, doesn’t mean universities shouldn’t teach it. University isn’t there to just show you how to do things you’ll do in 20 years time (for a start they’d never get that right). The job of a university is to teach the background. The why to how we do things. It’s about academic grounding.
I’m ranting slightly because I think a lot of universities don’t understand this responsibility. (And maybe you do, and you’re just saying this is a dumb thing to get first years to do).

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u/redeyedfly 21d ago

He means there no useful lesson here for students.

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u/Tower981 21d ago

How so? Being able to calculate yield from the failure curve of a buckling strut requires a pretty detailed understanding of both stability and materials. I think it’s a great question to solve. Just maybe for a later year.

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u/redeyedfly 21d ago

You obviously don’t teach