CROD, CBAR and CBEAM are one of the most popular 1d elements in Nastran. Reflecting real behaviour of structural is crucial for FEM. So, every finite element user needs to know the properties of the element types for modeling. Here is the table for 1d structural elements properties.
Feature | CBAR | CROD | CBEAM |
Degrees of Freedom (DOF) | Axial, bending, shear, torsion (6 DOFs/node) | Axial (tension/compression) and torsion | Axial, bending, shear, torsion (6 DOFs/node) |
Properties | Defined by PBAR or PBARL (rectangular, circular, etc.) | Defined by PROD (general area) | Defined by PBEAM or PBEAML (complex, user-defined sections supported) |
Material Properties | Defined via MAT1, MAT2, etc. | Defined via MAT1, MAT2, etc. | Defined via MAT1, MAT2, etc. |
Shear Stiffness | Accounted for, but simplified | Not included | Fully accounted for (shear deformation, warping, etc.) |
Torsional Stiffness | Included | Included | Fully accounted |
Applications | General-purpose beams, including bending, axial, torsion | Tension/compression-only members | Advanced beam problems with complex cross-sections and loadings |
Load Types | Axial, bending, torsion | Axial and torsion | Axial, bending, torsion, shear |
Mass Distribution | Distributed mass along length (via PBAR/PBARL) | Lumped mass per length unit | Distributed mass along length (via PBEAM/PBEAML) |
Boundary Conditions | Supports connections with 6 DOFs per node | Supports axial and torsional DOFs | Supports connections with 6 DOFs per node |
Complex Geometry | Moderate (straight or curved members) | Simple (straight members only) | High (can handle variable or custom cross-sections) |
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