Element End Release

Element end release introduces hinge behavior at an end of a beam or pipe element in Abaqus/Standard.

Element end release:

  • allows a rotational degree of freedom or a combination of rotational degrees of freedom to be released at one or both ends of an element or element set;

  • can be used in geometrically linear or nonlinear analysis; and

  • is available only for beam and pipe elements in Abaqus/Standard.

This page discusses:

 

See Also
About Kinematic Constraints
*RELEASE

Introduction

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 (n1, n2, t) for beam-type elements. The rotational degrees of freedom affected by the release are the rotation about the local n1-axis, the rotation about the local n2-axis, and the rotation about the local t-axis for beams in space. For beams in a plane, only the rotation about the local n1-axis is active (which coincides with rotations about the negative global z-axis).

Equivalent MPCS

If only one rotational degree of freedom is released, the kinematic constraint is equivalent to MPC type REVOLUTE plus MPC type PIN between two nodes. If two rotational degrees of freedom are released, the kinematic constraint is equivalent to MPC type UNIVERSAL plus MPC type PIN. If all rotational degrees of freedom are released, the kinematic constraint is equivalent to MPC type PIN. See General Multi-Point Constraints for details.

Identifying the Element End Involved in the Release

Either element sets or individual elements can be specified for a release definition. Degrees of freedom can be released at the first, second, or first and second ends of an element. The first end of the element, S1, is node 1 on the element as defined by the element connectivity; the second end, S2, is the last node (node 2 or 3, as appropriate) on the element. See Beam Element Library for a definition of the node ordering for beam elements.

Identifying the Local Rotational Degrees of Freedom Involved in the Release

Rotation combination codes rather than degrees of freedom are specified to identify the rotational degrees of freedom involved in the release.

M1

refers to the rotation about the n1-axis,

M2

refers to the rotation about the n2-axis,

M1-M2

refers to a combination of rotational degrees of freedom about the n1-axis and the n2-axis,

T

refers to the rotation about the t-axis,

M1-T

refers to a combination of rotational degrees of freedom about the n1-axis and the t-axis,

M2-T

refers to a combination of rotational degrees of freedom about the n2-axis and the t-axis, and

ALLM

represents a combination of all the rotational degrees of freedom (that is, M1, M2, and T).

Use with Transformed Coordinate Systems

Transformations applied to released nodes (Transformed Coordinate Systems) have no influence on the release. The release operates on the local degrees of freedom for the element.

Reading the Data from an Alternate Input File

The data for a release definition can be contained in a separate input file.