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Initial conditions, Type=stress

*Initial conditions, Type=stress, <option>
<element set>, <ic parameter 1>, ..., <ic parameter n>

Specify the initial values of initial stress at the integration points of an element or element set. Use one of the following options:

  • Homogeneous

    use this option to prescribe a homogeneous distribution of initial stress for a particular element set. The command line takes the following form:

    *Initial Conditions, Type = stress, Homogeneous

    <element set name>, sigma_{xx,0}, sigma_{yy,0}, sigma_{zz,0}

  • Geostatic

    Use this option to assign an elevation-dependent initial stress field to all members of a given element set. When a geostatic stress is prescribed for a particular element set, the stress in the vertical direction \(h\) (assumed to be the \(z\)-direction in 3-D and axisymmetric models and the \(y\)-direction in 2-D models) is assumed to vary piecewise linearly with this vertical coordinate. The command line takes the following form:

    *Initial Conditions, Type = stress, Geostatic

    <element set name>, h_1, sigma_0(h_1), h_2, sigma_0(h_2), K_{x,0}, K_{y,0}

    \(K_{x,0}\) and \(K_{y,0}\) are the lateral stress coefficients.

  • Full

    use this option to prescribe each component of the initial stress for a particular element set. The command line takes the following form:

    *Initial Conditions, Type = stress, Full

    <element set name>, sigma_{xx,0}, sigma_{yy,0}, sigma_{zz,0}, sigma_{xy,0}, sigma_{xz,0}, sigma_{yz,0}

  • User

    Use this option to specify the use of a user defined subroutine to define the initial stress field:

    *Initial Conditions, Type = stress, User

    The required user routine is described here.

  • File

    !!! "Upcoming release"

    This feature will be available with the upcoming release

    Use this option to import an integration-point stress field from a binary file written by *Restart write, stress:

    *Initial conditions, Type=stress, File=<filename>, Mesh=matching

    No data line follows this command. The Mesh=matching parameter is mandatory and identifies the currently available transfer method. Other mesh-transfer methods may be introduced as separate values in future versions.

    The source and target meshes have to match exactly. numgeo verifies the spatial dimension, node labels and coordinates, element labels, element types, connectivity, integration-point layout and stress-vector sizes before applying the imported field. A mismatch or a corrupt or incomplete file causes the import to be rejected.

    The file stores only the stress vectors. Strains, void ratio, constitutive state variables and other material-specific history are not transferred. These quantities have to be initialized separately when required by the constitutive model used in the target analysis.

    Use lower-case filenames and paths in the input command. For example, the stress field written after step 1 of the job mc_equilibrium can be imported using

    *Initial conditions, Type=stress, File=mc_equilibrium_restart/stress_step_1.bin, Mesh=matching