null3DFrame2

Background

The null3DFrame2 class creates a two-dimensional frame element with two-nodes. Each node has six degrees-of-freedom, for which three degree-of-freedom represents three translation in the X-, Y-, and Z-directions, and three rotation about X-,Y-, and Z-directions. However, this element provides no contribution to the stiffness matrix, mass matrix and damping matrix. This is

\[ \textbf{M}^\textrm{e} = \textbf{0}\,, \; \textbf{K}^\textrm{e} = \textbf{0} \,, \; \textbf{F}^\textrm{e} = \textbf{0} \,. \]

Note that \(\textbf{M}^\textrm{e}, \textbf{K}^\textrm{e} \in \mathbb{R}^{\textrm{N}_\textrm{dof}^\textrm{e} \times \textrm{N}_\textrm{dof}^\textrm{e}}\) with \(\textrm{N}_\textrm{dof}^\textrm{e} = 12\) in this case.

REFERENCE:

• Computers and Structures Inc., "Etabs extended three analysis of building system". None property at https://wiki.csiamerica.com/display/kb/None+property

Pre-Analysis

The python Pre-Analysis in the 01-Pre_Process/Method/Attach.py file provides with an interface to populate the Entities dictionary. This file contains several functions to populate specific fields. For example, to create a null3DFrame2, using json format, use:

• addElement(tag, name='null3DFrame2', conn, attributes):

  • tag : The identifier of this element, i.e., tag > -1
  • name : Seismo-VLAB element class name
  • conn : Connectivity array of this element

  Example

  A NULL3DFRAME2 element can be defined using the python interface as follows:
  SVL.addElement(tag=1, name='null3DFrame2', conn=[1,2], attributes={'section': 1})

  Application
  This element can be used when rigid link constraints are employed so that in the animation done in Paraview there is an element connecting. Also, this element can be used to transmit distributed load to adjacent elements or nodes.

On the contrary, the 01-Pre_Process/Method/Remove.py file provides with an interface to depopulate the Entities dictionary. For example, to remove an already define Element, use:

• delElement(tag):
  • tag : The identifier of the element to be removed, i.e., tag > -1

Run-Analysis

The C++ Run-Analysis in the 02-Run_Process/04-Elements/04-Frame/null3DFrame2.cpp file provides the class implementation. A null3DFrame2 element is created using the built-in json parse-structure provided in the Driver.hpp. A null3DFrame2 is defined inside the "Elements" json field indicating its "Tag" as follows,

• {
      "Elements": {
          "Tag": {
              "name" : "NULL3DFRAME2",
              "conn" : [ ]
          }
      }
  }
  

  Variable	Description
  Tag	Unique element object identifier.
  conn	The element connectivity node array.

  
  

  Attention

  This element can be used for display purposes when kinematic constraints are employed.

  The element (in the future) can be used unload distributed load that is applied to it.

  Example

  A NULL3DFRAME2 element between nodes 1 and 2 is constructed as:
  { "Elements": { "1": { "name" : "NULL3DFRAME2", "conn" : [1,2] } } }