15.5.2 Elbow element library

Product: ABAQUS/Standard  

References

Element types

ELBOW312-node pipe in space with deforming section, linear interpolation along the pipe
ELBOW323-node pipe in space with deforming section, quadratic interpolation along the pipe
ELBOW31B2-node pipe in space with ovalization only, axial gradients of ovalization neglected
ELBOW31C2-node pipe in space with ovalization only, axial gradients of ovalization neglected. This formulation is the same as that for element type ELBOW31B, with the exception that all odd numbered terms in the Fourier interpolation around the pipe but the first term are neglected.

Active degrees of freedom

1, 2, 3, 4, 5, 6

Additional solution variables

Elbow elements have numerous variables to model cross-sectional ovalization and warping. The number of variables depends on the type of elbow element, the number of nodes, and the number of Fourier modes chosen. In the following table is the number of Fourier modes:


Element typeNumber of variables
ELBOW3116, if =0
(16+8), if 1
ELBOW3224, if =0
(24+12), if 1
ELBOW31B 13+2, if =0,1
11+4, if 2
ELBOW31C13+2, if =0,1,3,5
15+2, if =2,4,6

Nodal coordinates required

Element property definition

Input File Usage:           
*BEAM SECTION, SECTION=ELBOW

Element-based loading

Distributed loads

Distributed loads are specified as described in Distributed loads, Section 19.4.3.


Load ID (*DLOAD):  BX

Units:  FL–3

Description:  Body force per unit volume in global -direction.


Load ID (*DLOAD):  BY

Units:  FL–3

Description:  Body force per unit volume in global -direction.


Load ID (*DLOAD):  BZ

Units:  FL–3

Description:  Body force per unit volume in global -direction.


Load ID (*DLOAD):  BXNU

Units:  FL–3

Description:  Nonuniform body force in global -direction with magnitude supplied via user subroutine DLOAD (DLOAD, Section 25.2.5).


Load ID (*DLOAD):  BYNU

Units:  FL–3

Description:  Nonuniform body force in global -direction with magnitude supplied via user subroutine DLOAD (DLOAD, Section 25.2.5).


Load ID (*DLOAD):  BZNU

Units:  FL–3

Description:  Nonuniform body force in global -direction with magnitude supplied via user subroutine DLOAD (DLOAD, Section 25.2.5).


Load ID (*DLOAD):  CENT

Units:  FL–4(ML–3T–2)

Description:  Centrifugal load (magnitude is input as , where is the mass density per unit volume and is the angular velocity).


Load ID (*DLOAD):  CENTRIF

Units:  T–2

Description:  Centrifugal load (magnitude is input as , where is the angular velocity).


Load ID (*DLOAD):  GRAV

Units:  LT–2

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


Load ID (*DLOAD):  HPE

Units:  FL–2

Description:  Hydrostatic external pressure, with linear variation in global (default closed-end condition).


Load ID (*DLOAD):  HPI

Units:  FL–2

Description:  Hydrostatic internal pressure, with linear variation in global (default closed-end condition).


Load ID (*DLOAD):  PE

Units:  FL–2

Description:  Uniform external pressure (default closed-end condition).


Load ID (*DLOAD):  PI

Units:  FL–2

Description:  Uniform internal pressure (default closed-end condition).


Load ID (*DLOAD):  PENU

Units:  FL–2

Description:  Nonuniform external pressure with magnitude supplied via user subroutine DLOAD (DLOAD, Section 25.2.5) (default closed-end condition).


Load ID (*DLOAD):  PINU

Units:  FL–2

Description:  Nonuniform internal pressure with magnitude supplied via user subroutine DLOAD (DLOAD, Section 25.2.5) (default closed-end condition).


Load ID (*DLOAD):  ROTA

Units:  T–2

Description:  Rotary acceleration load (magnitude is input as , where is the rotary acceleration).

ABAQUS/Aqua loads

ABAQUS/Aqua loads are specified as described in ABAQUS/Aqua analysis, Section 6.10.1.


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 elbow (node 1).


Load ID (*CLOAD/ *DLOAD):  FD2

Units:  F

Description:  Fluid drag force on the second end of the elbow (node 2 or node 3).


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 elbow (node 1).


Load ID (*CLOAD/ *DLOAD):  FI2

ABAQUS/CAE Load/Interaction:   

Units:  F

Description:  Fluid inertia force on the second end of the elbow (node 2 or node 3).


Load ID (*CLOAD/ *DLOAD):  PB

Units:  FL–1

Description:  Buoyancy force (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 elbow (node 1).


Load ID (*CLOAD/ *DLOAD):  WD2

Units:  F

Description:  Wind drag force on the second end of the elbow (node 2 or node 3).

Element output

The default stress output points are on the inside surface and the outside surface at all integration stations around the pipe.

Stress, strain, and other tensor components

Stress and other tensors (including strain tensors) are available for elements with displacement degrees of freedom. All tensors have the same components. For example, the stress components are as follows:

S11

Direct stress along the pipe.

S22

Direct stress around the pipe section.

S12

Shear stress in the pipe wall.


Section forces and moments

SF1

Axial force.

SM1

Bending moment about the local 1-axis.

SM2

Bending moment about the local 2-axis.

SM3

Twisting moment about the elbow axis.


Node ordering on elements

Numbering of integration points for output

The extrados is the side of the pipebend that is furthest away from the center of the torus defining the pipebend; that is, the side of the pipebend to which the -axis points. The intrados is the side of the pipebend closest to the center of the torus.

The middle surface integration points around a section are shown above. There is a default of five thickness direction integration points at each such point, with point 1 on the inside surface of the pipe and point 5 on the outside surface.

For ELBOW31 and ELBOW31B only one integration station is used along the axis of the element. For ELBOW32 two integration stations are used along the axis of the elbow and the point numbers on the second section are a continuation of those on the first section (e.g., 21, 22, …, 40 in the default case), located around the pipe as shown above.