BbarQuad u-p

bbarQuadUP is a four-node plane-strain mixed volume/pressure element, which uses a tri-linear isoparametric formulation. This element is implemented for simulating dynamic response of solid-fluid fully coupled material, based on Biot’s theory of porous medium. Each element node has 3 degrees-of-freedom (DOF): DOF 1 and 2 for solid displacement (u) and DOF 3 for fluid pressure (p).

Please click here for examples.

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

recorder Node <-file \(fileName&gt; &lt;-time&gt; &lt;-node (\)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 bbarQuadUP 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 bbarQuadUP $eleTag $iNode $jNode $kNode $lNode $thick $matTag $bulk $fmass $hPerm \(vPerm &lt;\)b1=0 $b2=0 \(t=0&gt;</strong></p></td> </tr> </tbody> </table> <table> <tbody> <tr class="odd"> <td><code class="parameter-table-variable">eleTag</code></td> <td><p>A positive integer uniquely identifying the element among all elements</p></td> </tr> <tr class="even"> <td><p><strong>\)iNode, $jNode, $kNode, \(lNode</strong></p></td> <td><p>Four element node (previously defined) numbers in counter-clockwise order around the element</p></td> </tr> <tr class="odd"> <td><code class="parameter-table-variable">thick</code></td> <td><p>Element thickness</p></td> </tr> <tr class="even"> <td><code class="parameter-table-variable">matTag</code></td> <td><p>Tag of an NDMaterial object (previously defined) of which the element is composed</p></td> </tr> <tr class="odd"> <td><code class="parameter-table-variable">bulk</code></td> <td><p>Combined undrained bulk modulus B&lt;sub&gt;c&lt;/sub&gt; relating changes in pore pressure and volumetric strain, may be approximated by:</p> <p>B&lt;sub&gt;c&lt;/sub&gt; &amp;asymp; B&lt;sub&gt;f&lt;/sub&gt;/n</p> <p>where B&lt;sub&gt;f&lt;/sub&gt; is the bulk modulus of fluid phase (2.2x10&lt;sup&gt;6&lt;/sup&gt; kPa (or 3.191x10&lt;sup&gt;5&lt;/sup&gt; psi) for water), and n the initial porosity.</p></td> </tr> <tr class="even"> <td><code class="parameter-table-variable">fmass</code></td> <td><p>Fluid mass density</p></td> </tr> <tr class="odd"> <td><p><strong>\)hPerm, \(vPerm</strong></p></td> <td><p>Permeability coefficient in horizontal and vertical directions respectively.</p></td> </tr> <tr class="even"> <td><p><strong>\)b1, $b2

Optional gravity acceleration components in horizontal and vertical directions respectively (defaults are 0.0)

t

Optional uniform element normal traction, positive in tension (default is 0.0)

TYPICAL RANGE OF PERMEABILITY COEFFICIENT

Gravel

Sand

Silty Sand

Silt

Clay

>1.0x10<sup>-1</sup> cm/s (or 3.94x10<sup>-2</sup> in/s)

1.0x10<sup>-3</sup> cm/s (or 3.94 x10<sup>-4</sup> in/s) ~ 1.0x10<sup>-1</sup> cm/s (or 3.94 x10<sup>-2</sup> in/s)

1.0x10<sup>-5</sup> cm/s (or 3.94 x10<sup>-6</sup> in/s) ~ 1.0x10<sup>-3</sup> cm/s (or 3.94 x10<sup>-4</sup> in/s)

1.0x10<sup>-7</sup> cm/s (or 3.94 x10<sup>-8</sup> in/s) ~ 1.0x10<sup>-5</sup> cm/s (or 3.94 x10<sup>-6</sup> in/s)

<1.0x10<sup>-7</sup> cm/s (or 3.94x10 <sup>-8</sup> in/s)

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


UC San Diego Soil Model:

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