PSA: Always use PIPE not CIRC for circular beam section

I’ve found that beams using PIPE with 0 ID (thickness = outer radius) is better than CIRC in *BEAM SECTION. Perhaps everyone should be advised to use PIPE for solid round bars?

Advantages of PIPE:

  • Bending moment is more accurate.
  • Doesn’t have the bug of rotational constraint being applied to the wrong DOF.
  • Doesn’t have the bug of wrong deformed shape with prescribed rotation.
  • Stress is more accurate.
  • More accurate frequencies with *FREQUENCY, including twisting modes.

Advantages of CIRC:

  • Looks like a circle.

Not quite a drop-in replacement because:

  • *DLOAD uses different areas. Scale the pressure to compensate.
  • Stress is only valid at the midside nodes of the ends, whereas for CIRC, it’s only valid at the corner and midspan nodes.

Have I overlooked any problems with PIPE?

it seems number of integration points of pipe sections of beam element are doubled compares to circle section types, so make it getting better results.

it may right for simple static analysis, but i still doubt in advanced analysis such as contact. I’m not yet further study in plasticity.

right, not to advised to do replacement. only recommended for general use but not for all cases.