Problem in bending analysis of beam

[Tinni1]

Hi,

I am performing a bending analysis of a cold-formed steel beam, simply supported at loaded at 3 different points (Picture of the model attached). The translational degree of freedom at X direction is restrained at both the ends of the beam.
For the loading point and support, I have modeled, semi-circular cylindrical objects with 3D-discrete rigid elements.
Between the rigid body and the beam, I have defined: penalty friction(co eff-0.35), normal hard contact property, and general contact for the explicit solver. I have not defined any tie constraint anywhere in the model.
I am using displacement control load and dynamic explicit analysis.

My analysis is aborted due to the below error.

1. Abaqus/Explicit requires rigid bodies to have a non-zero mass unless
translational constraints are applied with the *BOUNDARY option (see
the SIMULIA User Assitance Guide). Nodes that are part of a rigid
body do not require mass individually but the rigid body as a whole
must possess mass unless constraints are used. To remedy this error,
either add translational constraints to the reference nodes with the
*BOUNDARY option or add mass using the *MASS option, whichever is
appropriate to obtain the desired response. A node set named
"ErrNodeRefNodeNoMass" containing the problematic reference nodes is
created to help locate the error and modify the input definition.

2. Abaqus/Explicit requires rigid bodies to have positive definite
rotary inertia unless rotational constraints are applied with the
*BOUNDARY option (see the SIMULIA User Assitance Guide). Nodes that
are part of a rigid body do not require mass and inertia
individually, but the rigid body as a whole must possess positive
definite rotary inertia unless constraints are used. To remedy this
error, either add rotational constraints to the reference nodes with
the *BOUNDARY option or add inertia using the *ROTARY INERTIA
option, whichever is appropriate to obtain the desired response. A
node set named "ErrNodeRefNodeNoRot1Axis" containing the problematic
reference nodes is created to help locate the error and modify the
input definition.

How do I eliminate this error, could anyone provide any direction, please?

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1646481680/tips/Abaqus_beam_analysis_query_vs1j4m.docx[/url]

 

[FEA way]

Just apply point mass/inertia (you will find this in the Assembly container) to rigid body reference points and it will work.

 

[Tinni1]

Thanks,

What should be the magnitude of point mass? Does the magnitude matter?
What value of rotary inertia I should apply? Is it necessary to apply rotary inertia also?

 

[FEA way]

It should represent the actual mass/inertia of the parts to which it is applied. You can estimate it based on the shape and assumed material. Or mesh the parts with deformable elements and then assign rigid body constraint to them. Mass/inertia will be determined automatically from material density.

 

[Tinni1]

Great!, Many thanks for this!