u-p-U element

This command is used to construct a u-p-U element object, which include two types: eight node element and twenty node element.

For eight-node element:

element Brick8N_u_p_U $eleTag $node1 $node2 $node3 $node4 $node5 $node6 $node7 $node8 $matTag $bf1 $bf2 $bf3 $n $alpha $soildDens $fluidDens $k1 $k2 $k3 $K_fluid $P

For twenty-node element:

element Brick20N_u_p_U $eleTag $node1 $node2 $node3 $node4 $node5 $node6 $node7 $node8 $node9 $node10 $node11 $node12 $node13 $node14 $node15 $node16 $node17 $node18 $node19 $node20 $matTag $bf1 $bf2 $bf3 $n $alpha $soildDens $fluidDens $k1 $k2 $k3 $K_fluid $P

$eleTag	unique element object tag
$node1 $node2 $node3 $node4 $node5 $node6 $node7 $node8 ....	node coordinate (either eight or twenty), input order is shown in the figure
$matTag	material tag associated with previsouly-difined NDMaterial object
$bf1 $bf2 $bf3	body force in the direction of global coordinates x, y and z
$n	porosity
$alpha	1-Ks/Kt (ratio of void space =1 for soils, =0.6 for concrete...)
$soildDens	solid density
$fluidDens	fluid density
$k1 $k1 $k3	coefficient of permeability in the direction of x, y and z
$K_fluid	fluid bulk modulus
$P	pressure... not used currently (set to 0.0)

The valid queries to a Brick8N_u_p_U and Brick20N_u_p_U elements when creating an ElementRecorder object are 'force,' 'stiffness,' stress', 'gausspoint' or 'plastic'. The output is given as follows:

'stress'	the six stress components from each Gauss points are output by the order: sigma_xx, sigma_yy, sigma_zz, sigma_xy, sigma_xz,sigma_yz
'gausspoint'	the coordinates of all Gauss points are printed out
'plastic'	the equivalent deviatoric plastic strain from each Gauss point is output in the same order as the coordinates are printed