29.4.3 Frame element library

Product: Abaqus/Standard

References

Overview

This section provides a reference to the frame elements available in Abaqus/Standard.

Element types

Frame in a plane

FRAME2D 2-node straight frame element

Active degrees of freedom

1, 2, 6

Additional solution variables

Two additional variables relating to the axial and lateral displacements.

Frame in space

FRAME3D 2-node straight frame element

Active degrees of freedom

1, 2, 3, 4, 5, 6

Additional solution variables

Three additional variables relating to the axial and lateral displacements.

Nodal coordinates required

Frame in a plane: X, Y (Direction cosines of the normal are not used; any values given are ignored.)

Frame in space: X, Y, Z (Direction cosines of the normal are not used; any values given are ignored.)

Element property definition

Local orientations defined as described in “Orientations,” Section 2.2.5, cannot be used with frame elements to define local material directions. The orientation of the local section axes in space is discussed in “Frame elements,” Section 29.4.1.

Input File Usage:

*FRAME SECTION

Element-based loading

Distributed loads

Distributed loads are specified as described in “Distributed loads,” Section 34.4.3.

Load ID (*DLOAD):  GRAV

Units:  LT^–2

Description:  Gravity loading in a specified direction (magnitude is input as acceleration).

Load ID (*DLOAD):  PX

Units:  FL^–1

Description:  Force per unit length in global X-direction.

Load ID (*DLOAD):  PY

Units:  FL^–1

Description:  Force per unit length in global Y-direction.

Load ID (*DLOAD):  PZ

Units:  FL^–1

Description:  Force per unit length in global Z-direction (only for frames in space).

Load ID (*DLOAD):  P1

Units:  FL^–1

Description:  Force per unit length in frame local 1-direction (only for frames in space).

Load ID (*DLOAD):  P2

Units:  FL^–1

Description:  Force per unit length in frame local 2-direction.

Abaqus/Aqua loads

Abaqus/Aqua loads are specified as described in “Abaqus/Aqua analysis,” Section 6.11.1.

Load ID (*CLOAD/ *DLOAD):  FDD

Units:  FL^–1

Description:  Transverse fluid drag load.

Load ID (*CLOAD/ *DLOAD):  FD1

Units:  F

Description:  Fluid drag force on the first end of the frame (node 1).

Load ID (*CLOAD/ *DLOAD):  FD2

Units:  F

Description:  Fluid drag force on the second end of the frame (node 2).

Load ID (*CLOAD/ *DLOAD):  FDT

Units:  FL^–1

Description:  Tangential fluid drag load.

Load ID (*CLOAD/ *DLOAD):  FI

Units:  FL^–1

Description:  Transverse fluid inertia load.

Load ID (*CLOAD/ *DLOAD):  FI1

Units:  F

Description:  Fluid inertia force on the first end of the frame (node 1).

Load ID (*CLOAD/ *DLOAD):  FI2

Units:  F

Description:  Fluid inertia force on the second end of the frame (node 2).

Load ID (*CLOAD/ *DLOAD):  PB

Units:  FL^–1

Description:  Buoyancy load (closed-end condition).

Load ID (*CLOAD/ *DLOAD):  WDD

Units:  FL^–1

Description:  Transverse wind drag load.

Load ID (*CLOAD/ *DLOAD):  WD1

Units:  F

Description:  Wind drag force on the first end of the frame (node 1).

Load ID (*CLOAD/ *DLOAD):  WD2

Units:  F

Description:  Wind drag force on the second end of the frame (node 2).

Foundations

Foundations are specified as described in “Element foundations,” Section 2.2.2.

Load ID (*FOUNDATION):  FX

Units:  FL^–2

Description:  Stiffness per unit length in global X-direction.

Load ID (*FOUNDATION):  FY

Units:  FL^–2

Description:  Stiffness per unit length in global Y-direction.

Load ID (*FOUNDATION):  FZ

Units:  FL^–2

Description:  Stiffness per unit length in global Z-direction (only for frames in space).

Load ID (*FOUNDATION):  F1

Units:  FL^–2

Description:  Stiffness per unit length in frame local 1-direction (only for frames in space).

Load ID (*FOUNDATION):  F2

Units:  FL^–2

Description:  Stiffness per unit length in frame local 2-direction.

Element output

All element output variables are given at the element ends (nodes 1 and 2) and midpoint (node 3).

Section forces and moments

SF1	Axial force.

SF2	Transverse shear force in the local 2-direction.

SF3	Transverse shear force in the local 1-direction (only available for frames in space).

SM1	Bending moment about the local 1-axis.

SM2	Bending moment about the local 2-axis (only available for frames in space).

SM3	Twisting moment about the frame axis (only available for frames in space).

See “Frame elements with lumped plasticity,” Section 3.9.2 of the Abaqus Theory Guide, for a discussion of the section forces and moments.

Section elastic strains and curvatures

SEE1	Elastic axial strain.

SKE1	Elastic curvature change about the local 1-axis.

SKE2	Elastic curvature change about the local 2-axis (only available for frames in space).

SKE3	Elastic twist of the beam (only available for frames in space).

Plastic displacements and rotations in the element coordinate system

SEP1	Plastic axial displacement.

SKP1	Plastic rotation about the local 1-axis.

SKP2	Plastic rotation about the local 2-axis (only available for frames in space).

SKP3	Plastic rotation about the beam axis (only available for frames in space).

Section force and moment backstresses

SALPHA1

Axial force backstress.

SALPHA2

Bending moment backstress about the local 1-axis.

SALPHA3

Bending moment backstress about the local 2-axis (only available for frames in space).

SALPHA4

Twisting moment backstress about the beam axis (only available for frames in space).

Node ordering on elements

For frames in space an additional node may be given after a frame element's connectivity (in the element definition—see “Element definition,” Section 2.2.1) to define the approximate direction of the first cross-section axis, . See “Frame elements,” Section 29.4.1, for details.