Four Node Quad u-p Element
FourNodeQuadUP is a four-node plane-strain element using bilinear 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 $fileName> <-time> <-node ($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 quadUP 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 quadUP $eleTag $iNode $jNode $kNode $lNode $thick $matTag $bulk $fmass $hPerm $vPerm <$b1=0 $b2=0 $t=0>|
|$eleTag||A positive integer uniquely identifying the element among all elements|
|$iNode, $jNode, $kNode, $lNode||Four element node (previously defined) numbers in counter-clockwise order around the element|
|$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|
|$hPerm, $vPerm||Permeability coefficient in horizontal and vertical directions respectively.|
|$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
|>1.0x10-1 cm/s (or 3.94x10-2 in/s)||1.0x10-3 cm/s (or 3.94 x10-4 in/s) ~ 1.0x10-1 cm/s (or 3.94 x10-2 in/s)||1.0x10-5 cm/s (or 3.94 x10-6 in/s) ~ 1.0x10-3 cm/s (or 3.94 x10-4 in/s)||1.0x10-7 cm/s (or 3.94 x10-8 in/s) ~ 1.0x10-5 cm/s (or 3.94 x10-6 in/s)||<1.0x10-7 cm/s (or 3.94x10 -8 in/s)|
Code Developed by: UC San Diego (Dr. Zhaohui Yang):
UC San Diego Soil Model:
- Element Command
- 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)
- UC San Diego Saturated Undrained soil
- Related References