Use beam elements to model structures in which one dimension (the length) is significantly greater than the other two dimensions and in which the longitudinal stress is most important. Beam theory is based on the assumption that the deformation of the structure can be determined entirely from variables that are functions of position along the structure's length. For beam theory to produce acceptable results, the cross-section dimensions should be less than 1/10 of the structure's typical axial dimension. The following are examples of typical axial dimensions:
the distance between supports,
the distance between gross changes in cross-section, and
the wavelength of the highest vibration mode of interest.
ABAQUS beam elements assume that plane sections perpendicular to the axis of the beam remain plane during deformation.
Do not be confused into thinking that the cross-section dimensions should be less than 1/10 of a typical element length. A highly refined mesh may contain beam elements whose length is less than their cross-section dimensions, although this is not generally recommended—continuum elements may be more suitable in such a case.