.. include:: sub.txt ==================== BbarQuad u-p Element ==================== 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). .. function:: element('bbarQuadUP', eleTag,*eleNodes,thick, matTag, bulk, fmass, hPerm, vPerm,) :noindex: =================================== =========================================================================== ``eleTag`` |int| unique element object tag ``eleNodes`` |listi| a list of four element nodes in counter-clockwise order ``thick`` |float| Element thickness ``matTag`` |int| Tag of an NDMaterial object (previously defined) of which the element is composed ``bulk`` |float| Combined undrained bulk modulus Bc relating changes in pore pressure and volumetric strain, may be approximated by: :math:`B_c \approx B_f/n` where :math:`B_f` is the bulk modulus of fluid phase (:math:`2.2\times 10^6` kPa (or :math:`3.191\times 10^5` psi) for water), and n the initial porosity. ``fmass`` |float| Fluid mass density ``hPerm``, ``vPerm`` |float| Permeability coefficient in horizontal and vertical directions respectively. ``b1``, ``b2`` |float| Optional gravity acceleration components in horizontal and vertical directions respectively (defaults are 0.0) ``t`` |float| Optional uniform element normal traction, positive in tension (default is 0.0) =================================== =========================================================================== .. seealso:: `Notes `_