Cyclic ElastocPlasticity

This command is used to construct a multi-dimensional material object that that follows the constitutive behavior of a cyclic elastoplasticity model for large post- liquefaction deformation.

nDmaterial CycLiqCP $matTag $G0 $kappa $h $Mfc $dre1 $Mdc
        $dre2 $rdr $alpha $dir $ein <$rho>

CycLiqCP material is a cyclic elastoplasticity model for large post-liquefaction deformation, and is implemented using a cutting plane algorithm. The model is capable of reproducing small to large deformation in the pre- to post-liquefaction regime. The elastic moduli of the model are pressure dependent. The plasticity in the model is developed within the framework of bounding surface plasticity, with special consideration to the formulation of reversible and irreversible dilatancy.

The model has been validated against VELACS centrifuge model tests and has used on numerous simulations of liquefaction related problems.

When this material is employed in regular solid elements (e.g., FourNodeQuad, Brick), it simulates drained soil response. When solid-fluid coupled elements (u-p elements and SSP u-p elements) are used, the model is able to simulate undrained and partially drained behavior of soil.

During the application of gravity load (and static loads if any), the user is suggested to set the material behavior to be linear elastic, with the updateMaterialStage command:

updateMaterialStage -material $matTag -stage 0

After the gravity load stage, the material stage should be updated to achieve the desired elastic-plastic stress-strain response.

updateMaterialStage -material $matTag -stage 1


matTag

integer tag identifying material

G0

A constant related to elastic shear modulus

kappa

A constant related to elastic bulk modulus

h

Model parameter for plastic modulus

Mfc

Stress ratio at failure in triaxial compression

dre1

Coefficient for reversible dilatancy generation

Mdc

Stress ratio at which the reversible dilatancy sign changes

dre2

Coefficient for reversible dilatancy release

rdr

Reference shear strain length

alpha

Parameter controlling the decrease rate of irreversible dilatancy

dir

Coefficient for irreversible dilatancy potential

ein

Initial void ratio

rho

Saturated mass density

The material formulations for the CycLiqCP object are “ThreeDimensional” and “PlaneStrain”.


REFERENCES: Zhang J.M. and Wang G., 2012, “Large post-liquefaction deformation of sand, part I: physical mechanism, constitutive description and numerical algorithm”, Acta Geotechnica.


Code Developed by: Rui Wang, Tsinghua University

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