Beam element curvature

The curvature of beam elements is based on the orientation of the beam's $n_{2}$ -direction relative to the beam axis. If the $n_{2}$ -direction and the beam axis are not orthogonal (i.e., the beam axis and the tangent, $t$ , do not coincide), the beam element is considered to be curved initially. Since the behavior of curved beams is different from the behavior of straight beams, you should always check your model to ensure that the correct normals and, hence, the correct curvatures are used. For beams and shells Abaqus uses the same algorithm to determine the normals at nodes shared by several elements. A description is given in Beam Element Cross-Section Orientation.

If you intend to model curved beam structures, you should use one of the two methods described earlier to define the $n_{2}$ -direction directly, allowing you great control in modeling the curvature. Even if you intend to model a structure made up of straight beams, curvature may be introduced as normals are averaged at shared nodes. You can rectify this problem by defining the beam normals directly as explained previously.