Catenary mesh supported on 3 sides
Catenary mesh supported on 3 sides
(OP)
does anyone know where I can find an equation for horizontal tension reactions for a wire mesh used as a catenary and only supported on 3 sides? I have looked in Roark and can't seem to find anything. I have very limited experience with that book, so I may be looking in teh wrong place.
Any suggestions bould be greatly appreciated.
I have also tried modelling this in RAM Advanse, inputting 0.0000000001 for the Ig of a bending member trying to get it to act as a catenary, but that is not working.
Any suggestions bould be greatly appreciated.
I have also tried modelling this in RAM Advanse, inputting 0.0000000001 for the Ig of a bending member trying to get it to act as a catenary, but that is not working.






RE: Catenary mesh supported on 3 sides
I would model this as supported on two sides as this is how it will actally behave at the unsupported end.
You will actually get diagonal catenaries at the supported end corners (where this is shorter than ther main span). There will be no minor span catenaries as you need two horizontal reactions.
Hope this helps.
csd
RE: Catenary mesh supported on 3 sides
This is already in place, so I can't really specify anything different, I am just trying to make the numbers work.
RE: Catenary mesh supported on 3 sides
RE: Catenary mesh supported on 3 sides
This is really quite a nightmare to analyze. I initially said that I thought it should be checked as spanning one direction only, but my boss thinks it is getting support from bearing against the 4th side (even though it isn't connected), but I can't find any kind of formula that approximates this.
RE: Catenary mesh supported on 3 sides
I would design it as one way.
RE: Catenary mesh supported on 3 sides
of course the approach being suggested should be hand calc, no?
RE: Catenary mesh supported on 3 sides
RAM Advanse will apparently not do catenary action. It tells me that my deflections are very large (actually gives me a warning), but gives no reaction parallel to the member.
I can use Roark for a single catenary.
RE: Catenary mesh supported on 3 sides
These programs fail because of the type of second-order analysis that's used. They use geometric stiffness matrices to account for second-order effects. That won't work for something like a cable. The program must literally move the nodes and do something like Newton-rhapson (sorry if I mis-spelled that) iteration with the tangent stiffness.
RE: Catenary mesh supported on 3 sides
I have one more question. I am looking at Roark page 245 (7th edition), case 6. I am assuming that the P value is the horizontal reaction only and I need to combine that with the vertical reaction to get a resultant reaction.
Can anyone confirm this?
RE: Catenary mesh supported on 3 sides
csd
RE: Catenary mesh supported on 3 sides
RE: Catenary mesh supported on 3 sides
RE: Catenary mesh supported on 3 sides
If you know your initial mesh drape you can solve for the tensile force using the basic cable equation:
Moment = H*d = w*L*L/8
where:
H is the horizontal force at the support
d is the drape height
w is the uniform load on the mesh
RE: Catenary mesh supported on 3 sides
in the first site below you find a freshly added sheet for calculating a plate in pure membrane behaviour with support on three sides (look under Plates -> Membranes -> Rectangular -> 3 held sides).
This shouldn't be far from your problem, as the influence of shear, that's absent in a mesh, is not very important (and of course should be Poisson=0): it is also possible to derive a sheet with no shear contribution, if you are interested.
Would like to receive your comments upon, if you are still interested.
prex
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