.. _quad::

Quadrilateral Element
^^^^^^^^^^^^^^^^^^^^^

This command is used to construct a FourNodeQuad element object which uses a bilinear isoparametric formulation.

.. admonition:: Command

   element quad $eleTag $iNode $jNode $kNode $lNode $thick $type $matTag <$pressure $rho $b1 $b2>

.. csv-table:: 
   :header: "Argument", "Type", "Description"
   :widths: 10, 10, 40

   $eleTag, |integer|, unique element object tag
   $iNode $jNode $kNode $lNode, |integer|   four nodes defining element boundaries, input in counter-clockwise order around the element.
   $thick, |float|,  element thickness
   $type, |string|,  string representing material behavior. The type parameter can be either "PlaneStrain" or "PlaneStress."
   $matTag, |integer|, tag of nDMaterial
   $pressure, |float|, surface pressure (optional: default = 0.0)
   $rho, |float|,  element mass density (per unit volume) from which a lumped element mass matrix is computed (optional: default=0.0)
   $b1 $b2, |float|, constant body forces defined in the isoparametric domain (optional: default=0.0)


.. figure:: quad.png
	:align: center
	:figclass: align-center

	Quad Element Node Numbering

.. note::

   The optional arguments must either be all specified or none specified.

   Consistent nodal loads are computed from the pressure and body forces.

   The valid queries to a Quad element when creating an ElementRecorder object are 'forces', 'stresses,' and 'material $matNum matArg1 matArg2 ...' Where $matNum refers to the material object at the integration point corresponding to the node numbers in the isoparametric domain.

.. admonition:: Example 

   The following example constructs a quad element for use in a plane stress problem with tag **1** between nodes **1, 2, 3, 4** with an nDMaterial of tag **1**.

   1. **Tcl Code**

   .. code-block:: tcl

      element quad 1 1 2 3 4 "PlaneStress" 1 

   2. **Python Code**

   .. code-block:: python

      element('quad',1,1,2,3,4, 'PlaneStress', 1, b1, b2, b3)




Code Developed by: |mhs|