18.104.22.168. BbarBrick u-p Element¶
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.
element('bbarBrickUP', eleTag, *eleNodes, matTag, bulk, fmass, permX, permY, permZ, <bX=0, bY=0, bZ=0>)
unique element object tag
a list of eight element nodes
Tag of an NDMaterial object (previously defined) of which the element is composed
Combined undrained bulk modulus Bc relating changes in pore pressure and volumetric strain, may be approximated by: \(B_c \approx B_f/n\)
where \(B_f\) is the bulk modulus of fluid phase (\(2.2\times 10^6\) kPa (or \(3.191\times 10^5\) psi) for water), and n the initial porosity.
Fluid mass density
Permeability coefficients in x, y, and z directions respectively.
Optional gravity acceleration components in x, y, and z directions directions respectively (defaults are 0.0)