Beam and cable problem. HELP! 2

[Integrator62]

There is a cantilever beam. One end is Fixed and other end is supported by an Inclined cable.
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Loading is vertically downward at the Tip of beam, denoted as P. Beam and cable are not considered Rigid. So they are considered to be deformed.
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So due to P, Flexure stress will govern and bend the beam.
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And wire will be elongated so tension will govern. For very little deformation this horizontal component of Tension causes pure Compression on beam. And vertical component reduces the moment due to P.
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The more the beam gets deformed the Compression stress turns into flexure stress on beam.
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So there are two dependent Phenomena. And undoubtedly the condition is statically indeterminate for sure! And I cant find a way to solve it analytically!
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Is there is a way to attack this type of problem? Or is it possible to govern an equation? Has it been done? Please help.

 

[IRstuff]

Please do not post in multiple forums.

Is this for school?

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[Integrator62]

Ok.
No. For my thesis work.
Thanks.

 

[rb1957]

yes, singly redundant ... i'd apply unit force method.

this'd directly solve the vertical component of the cable load, which'd be good enough for a professional result, but maybe not if a school problem ... if so, don't ask here.

strain energy method would give you the correct result.

another day in paradise, or is paradise one day closer ?

 

[btrueblood]

Depending on the relative stiffness of beam vs. cable, could the compression load induced at the beam tip induce buckling-type instability?

 

[Integrator62]

Thanks.

 

[Integrator62]

Should not. Actually Im using this type of configuration for an aircraft structural member. In that member a Aluminium frame is considered to be installed at the Tip. So there should not be any buckling.

Thanks.

 

[rb1957]

there will be compression in the beam (and bending) from the cable. it might be small (if the cable isn't pretensioned), but under load it'll increase, and it could be a factor.

buckling and crippling and possibly beam-column effects.

"In that member a Aluminium frame is considered to be installed at the Tip." ... what does this mean ? your sketch showed a cable-stayed cantilever; is the more structure at the tip ??

another day in paradise, or is paradise one day closer ?

 

[Integrator62]

In this picture I didnt show it and hence I assumed that there is no local buckling. In fact there will be a stabilizer. For stabilizer attachment a aluminuim frame will be installed.
Thanks.

 

[rb1957]

do you mean a doubly cantilevered beam ?? (with a redundant cable brace ?)

or do yo mean at the fixed end of the cantilever ??

another day in paradise, or is paradise one day closer ?

 

[Integrator62]

No. I have made a CAD with approximated estimated value. This picture is attached. You can have an idea of the system from it.

The aluminium frame and How and where the wires will be connected is not considered actually. It can be with Stabilizer beams through frame holes. It will be designed later by me according to the results with the assumption of local buckling is not present.

Thanks

 

[rb1957]

this is SO different to your original sketch !

i think this is so redundant that FEA is the only way ... unless you can rationalise a very simple structure/loading.

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[Integrator62]

Thanks. Ill go for FEA then

 

[WKTaylor]

Integrator62... Hmmm... see if this article is of any value...

Design of radial-wire airship bulkheads...

http://arc.aiaa.org/doi/abs/10.2514/6.1987-2441

NOTE. I have seen a design manual for cable supported structures... just can't remember "where". Will scratch my brain... see if anything surfaces.

CAUTION.

The devil is in details, such as cluster-joint load-centers, collum eccentricities and torque, collum symmetry/stability, thermal expansion/contraction [including variations within wires/wire-groups/collums, etc], individual wire* stiffness, etc

*"WIRE" Note: do You intend to use solid wire [round or 'shaped' cross-section], conventional wire rope, anti-rotation wire-rope, etc? Steel, CRES, HRA, fiber filaments or rod, etc?

Regards, Wil Taylor

Trust Me! I'm an engineer!

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

Unfortunately, in science what You 'believe' is irrelevant û "Orion"

 

[Integrator62]

Thank you very much

Im going through the article!

First of all I have very poor idea about wires!
I use solid Round Wires. Wire ropes in market are too thick as much as I have seen! So wires like GI wires, binding wires is what I have chosen though these have a large elongation!
My chosen wires will be only tension members. Wont take any compression and torsion generally. So are not Anti rotation and rods.

They will not be pretensioned like spokes in wheel. So I have to let the Beam resist bending moment initially with a very low loadings and almost no deformation. But wires will be in operation when Loadings are getting larger in value and deformation is not negligible!

Thanks

 

[rb1957]

are the wires purely structural ? why no pretension ? (that's quite odd for cable stayed structures.)

what size of wire are you thinking ? i'm thinking a/c control cables are 3/16" dia, i'm sure you can get them 1/8" maybe 1/16".

personally i'd let the wires react all the bending, they'd be very efficient to doing this, and use the "beam" as a "king-pin" to react the compression due to the pre-tension.

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

Integrator62...

Suggest you consider using [in-practice or in-theory] CRES spring-wire per ASTM A313 Standard Specification for Stainless Steel Spring Wire.

NOTE.
This spec lists several alloys/strain-hardened variations for ~small diameter wire. In general, though, these various wires are hardened to roughly the same extreme-high-strength-stiffness/diameter and are made to very exacting standards of quality [metallurgy, surface finish, tolerances, etc].

Regards, Wil Taylor

Trust Me! I'm an engineer!

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

Unfortunately, in science what You 'believe' is irrelevant û "Orion"

 

[Integrator62]

I cant say how to Thank you rb1957

Yes purely structural. Dont want to make it pretensioned because of the complex design. I have shown a CAD design in the link below.

But Right now I am thinking of making it a little more complex and pretensioned. Hope It will work better.

 

[Integrator62]

Thanks, I am going for it wktaylor

 

[rb1957]

"I cant say how to Thank you" ... yes, you can ... "Like this post? Star it!" ... what we call LPS (Little Purple Star) ...

another day in paradise, or is paradise one day closer ?