beam with symmetry boundary conditions

[shash128]

Hello,

I am trying to simulate a straight beam with UDL (linear static), clamped at both ends (u1=0,u2=0,ur3=0).
When whole domain is considered, the results are correct. But, when symmetry boundary conditions are applied (left end: u1=0,u2=0,ur3=0), (right end at x=L/2 : u1=0,ur3=0), the deflections are incorrect.
Can someone point out as to what i am missing here ? Shouldn't deflections in both the cases be same ?

 

[Mustaine3]

Yeah, it should be equal. Something is wrong in your model.

x is normal to your symmetry plane? Have you tried the XSYMM option for the symmetry BC? Maybe the missing UR2=0 is important.

 

[shash128]

Hello,
yes x axis is normal to plane of symmetry.
Now i have tried with symm/antisymm bc. At left end encastre bc: u1=u2=u3=ur1=ur2=ur3=0,
at right end xsymm bc: u1=ur2=ur3=0. Still the result is incorrect. Correct value of max. deflection is 0.1042,
obtained value is 1.667. what am i missing here ?

 

[Mustaine3]

Is using NLGEOM making a difference?

Upload the model or a similar example if you can't find the reason for the problem.

 

[shash128]

Hello,
NLGEOM is off.
I have uploaded the file.

http://files.engineering.com/getfil...fe-4a93-87bc-2513f0c82724&file=linearbeam.cae

http://files.engineering.com/getfil...55-4af1-bd44-9c9782a4d8be&file=linearbeam.jnl

Analytical soln. for max. deflection is: qL⁴/384D_xx, q=1,L=100,E=30*10⁶,H=1,
D_xx=EH³/12

 

[Mustaine3]

The geometry was not updated properly, so the beam had the wrong length. Measure the length in postprocessing to verify.

When doing it correct, I get the same displacements.

 

[shash128]

yes, that was the issue. Thank you.