Abaqus Beam Bending - 2D and 3D

[Hansfishberg91]

Hello all,

I am trying to model a four-point bend beam test in Abaqus however am having difficulty interpreting the results. I have set up two different models:

2D Model - Plane Strain Elements, Forces are applied as point loads

3D Model - Exact same geometry as 2D Model with a depth, Forces applied as point loads on nodes through the depth of the beam (acting like line loads). The total force applied to each beam is exactly the same (measured by RF of supports).

Both models have the exact same material properties etc....

However the problem I am facing is that the 3D model requires MUCH more force (factor of 10) to produce the same stresses/displacements as the 2D model. I cannot figure out why this is as surely both models should behave the same?

Any ideas anyone?

 

[IceBreakerSours]

Is this a homework assignment?

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[Hansfishberg91]

Nope

 

[corus]

Plane stress elements, with a prescribed thickness, are probably better as plane strain assumes an infinite thickness.

 

[Hansfishberg91]

Reaction forces exactly the same showing loads are the same - still getting difference deflections/bending stresses

 

[48202096]

Hi IceBreakerSours
I am a civil engineer, recently i was trying to model a three-dimensional steel frame with rigid diaphragm, to do this i have to use Kinematic Coupling in ABAQUS. However i am geting some error. For example i define an extra RP(reference point) at each story level and constraint three dof (U1,U2,UR2)(2 translational and 1 vertical rotational dof) of the Coupling Node to the RP. However i think because of using the Kinematic constraint, The dof of RP is now activated which means that the dof that i am not constraint (U2,UR1,UR3) to can be free to translate and rotate, so i'm starting to get error due to the singularity problems. I try to fix the problem by providing a boundary condition to the unconstrained dof of the RP, however my result start to get ugly because the extra boundary that i specified (eg. i think the boundary condition provide an extra constraint to U2 which is the vertical displacement of my frame that is supposed to be independent with the constraint equation). I am performing an geometrical and material non-linear analysis.

I was just wondering if you have any thought to my problems.

Many Thanks.

Peter