Twenty Eight Node Brick u-p Element

• Command_Manual
  • Tcl Commands
  • Modeling_Commands
    • model
    • uniaxialMaterial
    • ndMaterial
    • frictionModel
    • section
    • geometricTransf
    • element
    • node
    • sp commands
      • fix
      • fixX
      • fixY
      • fixZ
    • mp commands
      • equalDOF
      • rigidDiaphragm
      • rigidLink
    • timeSeries
    • pattern
    • mass
    • block commands
      • block2D
      • block3D
    • region
    • rayleigh
  • Analysis Commands
    • constraints Command
    • numberer Command
    • system Command
    • test Command
    • algorithm Command
    • integrator Command
    • analysis Command
    • eigen Command
    • analyze Command
  • Output Commands
    • recorder
    • record
    • print
    • printA
    • logFile
    • RealTime_Output_Commands
  • Misc Commands
    • eleResponse Command
    • getTime Command
    • getEleTags Command
    • getNodeTags
    • loadConst Command
    • nodeCoord Command
    • nodeDisp Command
    • nodeVel Command
    • nodeAccel Command
    • nodeEigenvector Command
    • nodeBounds
    • print Command
    • remove Command
    • reset Command
    • testIter
    • testNorms
    • wipe Command
    • exit Command
  • DataBase Commands
    • Template:DataBaseCommandsMenu

---

Twenty_Eight_Node_BrickUP is a 20-node hexahedral isoparametric element.

The eight corner nodes have 4 degrees-of-freedom (DOF) each: DOFs 1 to 3 for solid displacement (u) and DOF 4 for fluid pressure (p). The other nodes have 3 DOFs each for solid displacement. 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 Twenty_Eight_Node_BrickUP 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 20_8_BrickUP $eleTag $Node1 … $Node20 $matTag $bulk $fmass $PermX $PermY $PermZ <$bX=0 $bY=0 $bZ=0>

$eleTag	A positive integer uniquely identifying the element among all elements
$Node1,… $Node20	20 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)

Code Developed by: UC San Diego (Dr. Zhaohui Yang):

---

UC San Diego Soil Model:

• Element Command
  • UC San Diego u-p element (saturated soil)
    • Four Node Quad u-p Element
    • Brick u-p Element
    • bbarQuad u-p Element
    • bbarBrick u-p Element
    • Nine Four Node Quad u-p Element
    • Twenty Eight Node Brick u-p Element

• NDMaterial Command
  • UC San Diego soil models (Linear/Nonlinear, dry/drained/undrained soil response under general 2D/3D static/cyclic loading conditions (please visit UCSD for examples)
    • PressureIndependMultiYield Material
    • PressureDependMultiYield Material
    • PressureDependMultiYield02 Material
  • UC San Diego Saturated Undrained soil
    • FluidSolidPorousMaterial
• Related References