PM4Silt Material (Beta)

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• This page has been moved to the new OpenSees documentation site

This command is used to construct a 2-dimensional PM4Silt material.

nDMaterial PM4Silt $matTag $S_u $Su_Rat $G_o $h_po $Den <$Su_factor $Patm $nu $nG $h0 $eInit $lambda $phicv $nb_wet $nb_dry $nd $Ado $ru_max $zmax $cz $ce $Cgd $ckaf $m_m $CG_consol>

$matTag	integer tag identifying material
Primary:
$S_u	Undrained shear strength
$Su_Rat	Undrained shear strength ratio. If both S_u and Su_Rat values are specified, the value of S_u is used.
$G_o	Shear modulus constant
$h_po	Contraction rate parameter
$Den	Mass density of the material
$Su_factor	Optional, Undrained shear strength reduction factor
$P_atm	Optional, Atmospheric pressure
Secondary:
$nu	Optional, Poisson's ratio. Default value is 0.3.
$nG	Optional, Shear modulus exponent. Default value is 0.75.
$h0	Optional, Variable that adjusts the ratio of plastic modulus to elastic modulus. Default value is 0.5.
$eInit	Optional, Initial void ratios. Default value is 0.90.
$lambda	Optional, The slope of critical state line in e-ln(p) space. Default value is 0.060.
$phicv	Optional, Critical state effective friction angle. Default value is 32 degrees.
$nb_wet	Optional, Bounding surface parameter for loose of critical state conditions, 1.0 ≥ $nb_wet ≥ 0.01. Default value is 0.8.
$nb_dry	Optional, Bounding surface parameter for dense of critical state conditions, $nb_dry ≥ 0. Default value is 0.5.
$nd	Optional, Dilatancy surface parameter $nd ≥ 0. Default value is 0.3.
$Ado	Optional, Dilatancy parameter. Default value is 0.8.
$ru_max	Optional, Maximum pore pressure ratio based on p'.
$z_max	Optional, Fabric-dilatancy tensor parameter
$cz	Optional, Fabric-dilatancy tensor parameter. Default value is 100.0.
$ce	Optional, Variable that adjusts the rate of strain accumulation in cyclic loading
$cgd	Optional, Variable that adjusts degradation of elastic modulus with accumulation of fabric. Default value is 3.0.
$ckaf	Optional, Variable that controls the effect that sustained static shear stresses have on plastic modulus. Default value is 4.0.
$m_m	Optional, Yield surface constant (radius of yield surface in stress ratio space). Default value is 0.01.
$CG_consol	Optional, Reduction factor of elastic modulus for reconsolidation. $CG_consol ≥ 1. Default value is 2.0.

The material formulation for the PM4Silt object is "PlaneStrain"

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Code Developed by: Long Chen, Pedro Arduino, U Washington

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Notes

• Valid Element Recorder queries are
  • stress, strain
  • alpha (or backstressratio) for <math>\mathbf{\alpha}</math>
  • fabric for <math>\mathbf{z}</math>
  • alpha_in (or alphain) for <math>\mathbf{\alpha_{in}}</math>

e.g.
 recorder Element -eleRange 1 $numElem -time -file stress.out  stress

• Elastic or Elastoplastic response could be enforced by

Elastic:	updateMaterialStage -material $matTag -stage 0
Elastoplastic:	updateMaterialStage -material $matTag -stage 1

• If default values are used for secondary parameters, the model must be initialized after elastic gravity stage by

setParameter -value 0 -ele $elementTag FirstCall $matTag

• Post-shake reconsolidation can be activated by

setParameter -value 1 -ele $elementTag Postshake $matTag

Example

Example 1	2D undrained monotonic direct simple shear test using one element
Example 2	2D undrained cyclic direct simple shear test using one element

References

R.W.Boulanger, K.Ziotopoulou. "PM4Silt(Version 1): A Silt Plasticity Model for Earthquake Engineering Applications". Report No. UCD/CGM-18/01 2018