# QuadWithSensitivity
This command is used to construct a 2D four-node quadrilateral element object based on a bilinear isoparametric formulation.
```tcl element quadWithSensitivity $eleTag $iNode $jNode $kNode $lNode $thick $type $matTag <$pressure $rho $b1 $b2> ```

tag

integer tag identifying an existing parameter.

iNode jnode kNode lNode

four nodes defining element boundaries (numbered following a counter-clockwise order around the element).

thick

element thickness (constant).

type

string representing material behavior. Valid options depend on the nDMaterial object and the corresponding available material formulations. The ‘type’ parameter can be either "PlaneStrain" or "PlaneStress".

matTag

tag associated with previously-defined NDMaterial object.

pressure

surface pressure (set temporarily equal to zero for DDM-based sensitivity analysis).

rho

element mass density (per unit volume) from which a lumped element mass matrix is computed (optional, default=0.0).

b1 b2

constant body forces defined in the isoparametric domain (optional, default=0.0).


All parameters are the same as those in the ‘quad’ element command. Currently there are no sensitivity parameters in the ‘quadWithSensitivity’ element command.