Element end release is used to model hinged connections (hinged in one, two,
or three orthogonal directions) at one or both ends of the element. By
releasing rotational degrees of freedom, an element end is allowed to rotate
freely relative to the node about the chosen degrees of freedom. Any rotational
degrees of freedom that are not released are shared with the node. You must be
careful not to release a given degree of freedom at a node for all elements
that share that node; otherwise, the node has no stiffness for that degree of
freedom and
Abaqus/Standard
issues zero pivot warning messages.

Element end release operates on the element local degrees of freedom. See
Beam element cross-section orientation
for a definition of the local axes (${n}_{1}$,
${n}_{2}$,
t) for beam-type elements. The rotational degrees of
freedom affected by the release are the rotation about the local
${n}_{1}$-axis,
the rotation about the local ${n}_{2}$-axis,
and the rotation about the local t-axis for beams in
space. For beams in a plane, only the rotation about the local
${n}_{1}$-axis
is active (which coincides with rotations about the negative global
z-axis).