ABAQUS User Subroutines Reference Manual  

1.1.17 SIGINI
User subroutine to define an initial stress field.

Product: ABAQUS/Standard  

References

Overview

User subroutine SIGINI:

  • will be called for user-subroutine-defined initial stress fields at particular material points (these are the effective stress values for soils analysis);

  • is called at the start of the analysis for each applicable material calculation point in the model; and

  • can be used to define all active initial stress components at material points as functions of coordinates, element number, integration point number, etc.

Stress components

The number of stress components that must be defined depends on the element type for which this call is being made. Part VI, “Elements,” of the ABAQUS Analysis User's Manual,” describes the element stresses. The order in which the components must be defined is the same as in the element definition. For example, in three-dimensional continuum elements six stress components must be defined in the order

Initial stress field equilibrium

You should ensure that the initial stress field is in equilibrium with the applied forces and distributed loads by using a static step or a geostatic step to check the equilibrium of the initial stress field before starting the response history. See “Geostatic stress state,” Section 6.7.2 of the ABAQUS Analysis User's Manual, for a discussion of defining initial equilibrium conditions for problems that include pore fluid pressure.

User subroutine interface

      SUBROUTINE SIGINI(SIGMA,COORDS,NTENS,NCRDS,NOEL,NPT,LAYER,
     1 KSPT,LREBAR,NAMES)
C
      INCLUDE 'ABA_PARAM.INC'
C
      DIMENSION SIGMA(NTENS),COORDS(NCRDS)
      CHARACTER NAMES(2)*80


      user coding to define SIGMA(NTENS)


      RETURN
      END

Variables to be defined

SIGMA(1)

First stress component.

SIGMA(2)

Second stress component.

SIGMA(3)

Third stress component.

Etc.

Only NTENS stress values should be defined, where NTENS depends on the element type.

Variables passed in for information

COORDS

An array containing the initial coordinates of this point.

NTENS

Number of stresses to be defined, which depends on the element type.

NCRDS

Number of coordinates.

NOEL

Element number.

NPT

Integration point number in the element.

LAYER

Layer number (for composite shells and layered solids).

KSPT

Section point number within the current layer.

LREBAR

Rebar flag. If LREBAR=1, the current integration point is associated with element rebar. Otherwise, LREBAR=0.

NAMES(1)

Name of the rebar to which the current integration point belongs, which is the name given in the rebar or rebar layer definition (“Defining reinforcement,” Section 2.2.3 of the ABAQUS Analysis User's Manual, or “Defining rebar as an element property,” Section 2.2.4 of the ABAQUS Analysis User's Manual). If no name was given in the rebar or rebar layer definition, this variable will be blank. This variable is relevant only when LREBAR=1.