BbarBrick u-p Element

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bbarBrickUP is a 8-node mixed volume/pressure element, which uses a tri-linear isoparametric formulation.

Each node has 4 degrees-of-freedom (DOF): DOFs 1 to 3 for solid displacement (u) and DOF 4 for fluid pressure (p). This element is implemented for simulating dynamic response of solid-fluid fully coupled material, based on Biot's theory of porous medium.

Please click here for examples.

OUTPUT INTERFACE:

Pore pressure can be recorded at an element node using OpenSees Node Recorder:

recorder Node <-file $fileName> <-time> <-node ($nod1 $nod2 …)> -dof 3 vel

See OpenSees command manual (McKenna and Fenves 2001) for nodal displacement, velocity, or acceleration recorders.

The valid queries to a bbarBrickUP element when creating an ElementRecorder are 'force', 'stiffness', or 'material matNum matArg1 matArg2 ...', where matNum represents the material object at the corresponding integration point.

element bbarBrickUP $eleTag $Node1 $Node2 $Node3 $Node4 $Node5 $Node6 $Node7 $Node8 $matTag $bulk $fmass $PermX $PermY $PermZ <$bX=0 $bY=0 $bZ=0>

$eleTag	A positive integer uniquely identifying the element among all elements
$Node1,… $Node8	Eight element node (previously defined) numbers (see figure above for order of numbering).
$matTag	Tag of an NDMaterial object (previously defined) of which the element is composed
$bulk	Combined undrained bulk modulus Bc relating changes in pore pressure and volumetric strain, may be approximated by: Bc ≈ Bf/n where Bf is the bulk modulus of fluid phase (2.2x106 kPa (or 3.191x105 psi) for water), and n the initial porosity.
$fmass	Fluid mass density
$permX, $permY, $permZ	Permeability coefficients in x, y, and z directions respectively.
$bX, $bY, $bZ	Optional gravity acceleration components in x, y, and z directions directions respectively (defaults are 0.0)

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Return to:

• Element Command
  • u-p Elements
  • Four Node Quad u-p Element
  • Brick u-p Element
  • Brick Large Displacement u-p Element
  • bbarQuad u-p Element
  • bbarBrick u-p Element
  • Twenty Node Brick u-p Element
  • Nine Four Node Quad u-p Element
  • Twenty Eight Node Brick u-p Element
  • SSPquadUP Element
  • SSPbrickUP Element