*PIPE-SOIL STIFFNESS

Define constitutive behavior for pipe-soil interaction elements.

This option is used to define the constitutive behavior for pipe-soil interaction elements. It can be used only in conjunction with the PIPE-SOIL INTERACTION option. Repeat the option as needed to define behavior in the different local directions.

This page discusses:

Optional parameters

DEPENDENCIES

Set this parameter equal to the number of field variable dependencies included in the definition of the material property values. If this parameter is omitted, it is assumed that the properties are independent of field variables. See Using the DEPENDENCIES parameters to define field variable dependence in Material Data Definition for more information.

DIRECTION

Set this parameter equal to the direction in the local orientation system for which the behavior is defined. The DIRECTION parameter can be set equal to a label or to a numerical value. Omit the DIRECTION parameter to define an isotropic model. The DIRECTION parameter must be used to define a constitutive model using the ASCE formulae.

Set DIRECTION=AXIAL (or DIRECTION=1) to specify behavior along the first local direction.

Set DIRECTION=VERTICAL (or DIRECTION=2) to specify behavior along the second local direction.

Set DIRECTION=HORIZONTAL (or DIRECTION=3) to specify behavior along the third local direction.

TYPE

Set TYPE=LINEAR (default) to define a linear constitutive model.

Set TYPE=NONLINEAR to define a nonlinear constitutive model.

Set TYPE=CLAY to define a constitutive model using the ASCE formulae for clay. This parameter must be used in conjunction with the DIRECTION parameter.

Set TYPE=SAND to define a constitutive model using the ASCE formulae for sand. This parameter must be used in conjunction with the DIRECTION parameter.

Set TYPE=USER to indicate the constitutive behavior is defined in user subroutine UMAT.

The following optional parameters can be used only in combination with TYPE=USER

PROPERTIES

Set this parameter equal to the number of property values needed as data in user subroutine UMAT. The default is PROPERTIES=0.

VARIABLES

Set this parameter equal to the number of solution-dependent variables that must be stored for the material calculations in user subroutine UMAT. The default is VARIABLES=1.

Data lines to define linear constitutive behavior (TYPE=LINEAR)

First line

  1. Interaction stiffness (force per relative displacement) corresponding to positive relative displacements, Kp.

  2. Interaction stiffness (force per relative displacement) corresponding to negative relative displacements, Kn. The default is Kn=Kp.

  3. Temperature.

  4. First field variable.

  5. Second field variable.

  6. Etc., up to five field variables.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than five)

  1. Sixth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the stiffness as a function of temperature and other predefined field variables.

Data lines to define nonlinear constitutive behavior (TYPE=NONLINEAR)

First line

  1. Force per unit length along pipeline.

  2. Relative displacement.

  3. Temperature.

  4. First field variable.

  5. Second field variable.

  6. Etc., up to five field variables.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than five)

  1. Sixth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the force per unit length as a function of relative displacement, temperature, and other predefined field variables.

Data lines to define constitutive behavior using the ASCE formula for sand in the axial direction (TYPE=SAND, DIRECTION=AXIAL)

First line

  1. Effective unit weight of soil, γ¯.

  2. Coefficient of soil pressure at rest, K0.

  3. Interface angle of friction, δ. Give the value in degrees.

  4. External pipe diameter, D.

  5. Ultimate relative displacement, ε¯a.

  6. Temperature.

  7. First field variable.

  8. Second field variable.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than two)

  1. Third field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the parameters for the ASCE formulae as a function of temperature and other predefined field variables.

Data lines to define constitutive behavior using the ASCE formula for clay in the axial direction (TYPE=CLAY, DIRECTION=AXIAL)

First line

  1. Undrained soil shear strength, S.

  2. Empirical adhesion factor, α.

  3. External pipe diameter, D.

  4. Ultimate relative displacement, ε¯a.

  5. Temperature.

  6. First field variable.

  7. Second field variable.

  8. Third field variables.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than three)

  1. Fourth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the parameters for the ASCE formulae as a function of temperature and other predefined field variables.

Data lines to define constitutive behavior using the ASCE formula for sand in the vertical direction (TYPE=SAND, DIRECTION=VERTICAL)

First line

  1. Total unit weight of soil, γ.

  2. Bearing capacity factor, Nq.

  3. Bearing capacity factor, Nγ.

  4. Vertical uplift factor, Nq⁢v.

  5. Ultimate relative displacement for downward motion, ε¯v⁢p.

  6. Ultimate relative displacement for upward motion, ε¯v⁢n.

  7. Temperature.

  8. First field variable.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than one)

  1. Second field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the parameters for the ASCE formulae as a function of temperature and other predefined field variables.

Data lines to define constitutive behavior using the ASCE formula for clay in the vertical direction (TYPE=CLAY, DIRECTION=VERTICAL)

First line

  1. Bearing capacity factor, Nc.

  2. Vertical uplift factor, Nc⁢v.

  3. Ultimate relative displacement for downward motion, ε¯v⁢p.

  4. Ultimate relative displacement for upward motion, ε¯v⁢n.

  5. Temperature.

  6. First field variable.

  7. Second field variable.

  8. Third field variable.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than three)

  1. Fourth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the parameters for the ASCE formulae as a function of temperature and other predefined field variables.

Data lines to define constitutive behavior using the ASCE formula for sand in the horizontal direction (TYPE=SAND, DIRECTION=HORIZONTAL)

First line

  1. Horizontal bearing capacity factor, Nq⁢h.

  2. Ultimate relative displacement, ε¯h.

  3. Temperature.

  4. First field variable.

  5. Second field variable.

  6. Etc., up to five field variables per line.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than five)

  1. Sixth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the parameters for the ASCE formulae as a function of temperature and other predefined field variables.

Data lines to define constitutive behavior using the ASCE formula for clay in the horizontal direction (TYPE=CLAY, DIRECTION=HORIZONTAL)

First line

  1. Horizontal bearing capacity factor, Nc⁢h.

  2. Ultimate relative displacement, ε¯h.

  3. Temperature.

  4. First field variable.

  5. Second field variable.

  6. Etc., up to five field variables per line.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than five)

  1. Sixth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define parameters for the ASCE formulae as a function of temperature and other predefined field variables.

Data lines if the constitutive behavior is defined in user subroutine UMAT (TYPE=USER)

First line

  1. Enter the data to be used as properties in user subroutine UMAT.

Repeat this data line as often as necessary to define properties required in UMAT. Enter eight values per line.

 

See Also
Pipe-Soil Interaction Elements
Pipe-Soil Interaction Element Library
UMAT
*PIPE-SOIL INTERACTION