Which of these structures is stronger? 1

[edison123]

Which of these structures is stronger in terms of resisting the bending?

Muthu

http://www.edison.co.in

 

[civeng80]

In terms of bending i.e. bending moment they would be the same.

 

[CrabbyT]

A, because the direction of the force puts the arch into tension.

In B, the arch would try to splay out, and my gut feeling is that this would induce some additional bending into the adjacent line segments (kind of like a P delta effect).

 

[LearningAlways]

B, arch in compression, no bending at mid span.

 

[edison123]

Thank you all.

Now, there are 3 conflicting opinions. Still confused.

Muthu

http://www.edison.co.in

 

[edison123]

Like arch bridges, isn't B better? (not a structural engineer alert)

Muthu

http://www.edison.co.in

 

[edison123]

Now to make it more complicated, imagine if the whole structure is rotating anti-clockwise.

Muthu

http://www.edison.co.in

 

[hokie66]

Crabby T is correct. But only because B is more likely to have stability issues. This would depend mostly on the structure width, which is undefined in the OP.

 

[rb1957]

either ... how symmetric is the material in tension and compression ? For many metals Fcy is lower than Fty
Then how symmetric is the cross section ? If square of round then then results different from T (or L or Pi).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[civeng80]

The OP wants to know which is stronger in terms of bending not failure. Of course there would be a different failure mode in each one.

 

[Just Some Nerd]

B if done as a reinforced concrete section? The corner joints at the ends of the arch are opening in A but closing in B, and I prefer a concrete arch in compression.

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Why yes, I do in fact have no idea what I'm talking about

 

[phamENG]

Not enough information. If stability isn't an issue, they'd likely be the same.

Is there a reason? Where did this come from?

 

[edison123]

More info. The material is 3 mm thick 40 mm wide copper in a commutator brazed at both ends as below.

Muthu

http://www.edison.co.in

 

[phamENG]

Commutator... that's a word I haven't used in a bit.

They'll be about the same globally, but you're likely to get local bending of the fins.

 

[edison123]

Failure modes. CW rotation when this happened. Would this failure happen in ACW rotation?

Muthu

http://www.edison.co.in

 

[SWComposites]

Why in tarnation couldn’t you have posted all of that info in the first post??

 

[SWComposites]

Weird failure mode for a metal. Why am I seeing what looks like delaminations?

And why is one area grey? Local heat damage?

 

[3DDave]

Looks more like an electrical failure, possibly from cooling spaces blocked with paint.

Is that also a groove? Orthographic pictures make for optical illusions.

How is there force applied to the middle?

 

[edison123]

The copper cracked in those areas while the current was flowing resulting in flashover. The force was rotational stress?

Muthu

http://www.edison.co.in

 

[phamENG]

No, that's not structural...not unless you have debris in the housing that impacted the commutator. Was that brazed in section a repair, or original manufacturing? Could be a low quality copper sheet or sheets laminated together. One comes apart while it's rotating, flashover, and boom - local damage to several. But I think your original question is unrelated.