ZeroLength Section Element
^^^^^^^^^^^^^^^^^^^^^^^^^^

This command is used to construct a zero length element object, which is defined by two nodes at the same location. The nodes are connected by a single section object to represent the force-deformation relationship for the element.



.. function:: element zeroLengthSection $eleTag $iNode $jNode $secTag <-orient $x1 $x2 $x3 $yp1 $yp2 $yp3> <-doRayleigh $rFlag>


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

   $eleTag, |integer|, unique element object tag
   $endNodes, |integerList|, 2 end nodes
   $secTag, |integer|, tag associated with previously-defined Section object
   $x, |floatList|,  (optional) 3 components in global coordinates defining local x-axis 
   $yp, |floatList|, "| (optional) 3 components in global coordinates defining vector yp 
   | which lies in the local x-y plane for the element."
   $rFlag, |integer|, "| optional, default = 0
   | rFlag = 0 NO RAYLEIGH DAMPING (default)
   | rFlag = 1 include rayleigh damping"


.. note::
   If the optional orientation vectors are not specified, the local element axes coincide with the global axes. Otherwise the local z-axis is defined by the cross product between the vectors x and yp vectors specified on the command line.

   The section force-deformation response represented by section string P acts along the element local x-axis, and the response for code Vy along the local y-axis. The other modes of section response follow from this orientation.

   The valid queries to a zero-length element when creating an ElementRecorder object are 'force,' 'deformation,' 'stiff,' and 'section $secArg1 secArg2 ...'.


.. warning::
   If the distance between end noes is not **0.0** a warning message will appear when the script is run. This is just a warning in case you have made a mistake as most users when they use zeroLength elements are wanting to use them in the more normal way. ZeroLength elements can be used between nodes with non-zero length.


.. admonition:: Example 

   The following examples demonstrate the commands in a script to add three zeroLength elements to domain. The three to be added have element tags **1**, **2**, and **3**. Element **1** has nodes **2** and **3** as its end ndes, has two materials **5** and **6** acting in directions **1** and **2**. Element **2** has as its end nodes **4** and **5**, has only one material **1** acting in direction **1**, the element has a global orientation.

   1. **Tcl Code**

   .. code-block:: none

      element zeroLengthSection 1 2 4 6
      element zeroLengthSection 2 4 5 6 -orient 1 1 0 -1 1 0
      element zeroLengthSection 2 4 5 6 -orient 1 1 0 -1 1 0 -doRayleigh 1



Code Developed by: |mhs|