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Bernoulli-Euler beam modeling (without transverse shear)
 
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ivan.stepanenko
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Joined: 11 Jun 2014
Posts: 10

PostPosted: Fri May 22, 2015 8:18 am  Reply with quote

Hello everebody,

Is anybody dealed with modeling Bernoulli-Euler beam in ANSYS for 3D space problems? Current ANSYS beam elements are BEAM188 and BEAM189 and both of them include transverse shear as Timoshenko beam, but I want to suppress this effect to model exact Bernoulli-Euler beam.
The problem that I encountered is creation beam structure in 3D space if I know EIz, EIy, GJ beam stiffnesses (corresponding to vertical bending stiffness, horizontal bending stiffness and torsional stiffness) as functions of local x beam coordinate. These stiffnesses were obtaned when complex 3D-structure was analyzed under different loading and boundary conditions, so it is possible to say that Bernoulli-Euler beam with these stiffnesses will show the same behaviour as an initial 3D-structure.
The way I tried to perform it in ANSYS is the following:
1) Creation of generalized beam sections when assuming some value of E and G. For example, if EIz=200e9 N*m^2, EIy=400 N*m^2, GJ=50e9 N*m^2 I can enter Izz=200, Iyy=400, J=50 assuming E=1e9 N/m^2 and G=1e9 N/m^2
2) Creation of isotropic material with E and G assumed at step 1. For example, if E=1e9 and G=1e9, I should enter in ANSYS EX=1e9 and PR=-0.5
3) Creation of BEAM188 or BEAM189 elements with sections created at step 1 and material created at step 2.

But when I use that method I still have problem that value of G affects at bending displacements because of transverse shear. I can suppress transverse shear behaviour by assigning Poisson ratio close to -1 (-0.95 for example) to tend G to infinity but I still have some problems.

I found that old BEAM4 element shows the behaviour similar to what I want but unfortunately it is no longer supported in ANSYS 14.

I would be grateful for any possible help.
_________________
Best regards,
Stepanenko Ivan,
Central Aerohydrodynamic Institute (TsAGI),
Department of Ensuring the Safety of Aeroelastic Phenomena, Engineer
140180, Russian Federation, Moscow Region, Zhulovsky city, 1 Zhukovsky Street, TsAGI
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Martin Liddle
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Joined: 15 Aug 2008
Posts: 1274
Location: Chesterfield, UK

PostPosted: Fri May 22, 2015 9:26 am  Reply with quote

On 22/05/2015 16:18, ivan.stepanenko wrote:
Quote:
I found that old BEAM4 element shows the behaviour similar to what I want but unfortunately it is no longer supported in ANSYS 14.
BEAM4 is available in ANSYS14; look in the Feature Archive. Like many
old elements it is no longer in the main documentation but it should
work fine.

--
Martin Liddle, Tynemouth Computer Services,
Chesterfield, Derbyshire, UK.
www.tynecomp.co.uk

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Martin Liddle, Tynemouth Computer Services,
Chesterfield, UK.
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ivan.stepanenko
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Joined: 11 Jun 2014
Posts: 10

PostPosted: Fri May 22, 2015 11:28 pm  Reply with quote

Thank you Martin!

Indeed, BEAM4 is still available in ANSYS14, so my problem is succesfully resolved.
_________________
Best regards,
Stepanenko Ivan,
Central Aerohydrodynamic Institute (TsAGI),
Department of Ensuring the Safety of Aeroelastic Phenomena, Engineer
140180, Russian Federation, Moscow Region, Zhulovsky city, 1 Zhukovsky Street, TsAGI
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