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<a name = "hj-top"> </a><table class = "table1" id = "table11"><tr><td><table class = "DocHeader"><tr><td class = "DocHeader1" colspan = "2"><h1>Defining a Rib Design Constraint</h1></td></tr><tr><td class = "DocHeader4" colspan = "2"/></tr><tr><td class = "DocHeader3"><table class = "DocHeaderIntro" id = "table12"><tr><td class = "Intro1"><p class = "header"><p class = "abstract">
<span class = "shortdesc">
You can define a rib restriction to obtain rib patterns in the optimization result.
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</p>
<p>This task shows you how to:
					</p><ul><li><a href = "#tso-c-user-TopOpt-DesArea-Rib-def" id = "toc_rg" title = "">Rib Restriction Definition</a></li><li><a href = "#tso-c-user-TopOpt-DesArea-Rib_example" id = "toc_rg" title = "">Example: Rib Definition</a></li></ul>
</p></td></tr><tr><td class = "Intro2"><hr class = "header"/><span class = "run-in-beforeyoubegin">Before you begin: </span>
The rib pattern restriction can only be used with the sensitivity-based algorithm.
</td></tr></table></td><td class = "DocHeader2"><table class = "DocTopicsSeeAlso" id = "table13"><tr><td class = "TopicsTitle">See Also</td></tr><tr><td><a title = "The rib restriction gives the user the possibility to obtain optimization results that contain rib patterns." href = "tso-c-user-TopOpt-DesArea-Rib.htm#tso-c-user-TopOpt-DesArea-Rib">About Rib Design</a></td></tr></table><table class = "DocTopicsInOtherGuides" id = "table14"><tr><td height = "8px"/></tr><tr><td class = "TopicsTitleNormal">In Other Guides</td></tr><tr><td><a title = "Defines restrictions of the design variables in topology optimization." href = "../TsoCmdMap/tso-r-cmd-dvconTopo.htm#tso-r-cmd-dvconTopo">DVCON_TOPO</a></td></tr></table></td></tr></table>




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<article class = "topic task nested1" aria-labelledby = "ariaid-title2" id = "tso-c-user-TopOpt-DesArea-Rib-def">
<h2 class = "title topictitle2">Rib Restriction Definition</h2>

<div class = "body taskbody">
<section><ol class = "ol steps"><li class = "li step stepexpand">

Using the graphical user interface choose <span class = "ph menucascade"><span class = "ph uicontrol">Command</span><abbr title = "and then"> &gt; </abbr><span class = "ph uicontrol">DVCON_TOPO</span></span> in
<span class = "ph">Tosca Structure.pre</span>
and define the rib restriction with the available fields shown in the following figure:
<br/><img class = "image" src = "../TsoUserImages/topoDvconRibGui.png" width = "800"/><br/>

</li><li class = "li step stepexpand">
Or use the <code class = "ph codeph">DVCON_TOPO</code> command:

<p>
<pre class = "codeblock">
<code class = "ph codeph">DVCON_TOPO
  ID_NAME         = &lt;Name of DVCON object&gt;
  EL_GROUP        = &lt;Element group to be restricted&gt;
  CHECK_TYPE      = RIB_DESIGN
  CHECK_GROUP     = &lt;Element group to be checked for restriction&gt;
  RIB_THICKNESS   = &lt;averaged thickness of ribs&gt;
  RIB_DISTANCE    = &lt;averaged distance of rib centers&gt;
  RIB_DIRECTION   = &lt;X_COMP&gt;, &lt;Y_COMP&gt;, &lt;Z_COMP&gt;
  RIB_CS          = &lt;name_of_coordinate_system&gt;
END_</code>
</pre>
</p>
</li><li class = "li step stepexpand">
A rib restriction is activated by setting the <code class = "ph codeph">CHECK_TYPE</code> of the design
variable constraint to <code class = "ph codeph">RIB_DESIGN</code>. The restriction definition contains the
following parameters:
<ol type = "a" class = "ol substeps">
<li class = "li substep">
<code class = "ph codeph">ELEMENT_GROUP</code>: The group of elements for which the constraint is active.
Defining an element group is mandatory.
</li>
<li class = "li substep">
<code class = "ph codeph">CHECK_GROUP</code>: The group of elements that are checked if elements are properly
supported and do not violate the rib restriction. Most often it is best to use the same group as in
<code class = "ph codeph">ELEMENT_GROUP</code>. All elements are used if this parameter is empty.
</li>
<li class = "li substep">
<code class = "ph codeph">RIB_THICKNESS</code>: The averaged thickness of the ribs.
</li>
<li class = "li substep">
<code class = "ph codeph">RIB_DISTANCE</code>: The averaged distance between the rib centers. The distance must be larger than twice the average element edge length.

</li>
<li class = "li substep">
<code class = "ph codeph">RIB_DIRECTION</code>: Out-of-plane growth direction of the ribs.
</li>
<li class = "li substep">
  
    <code class = "ph codeph">RIB_CS</code>: Coordinate system for the definition of the rib direction.
  
<div class = "itemgroup stepresult">
<table class = "Remark" id = "table132"><tr><td class = "Remark"><span class = "run-in.important">Important:
				</span><span class = "notecontent"> It is only required to define an additional volume/ mass constraint for the
                  design area when its constraint value is below <code class = "ph codeph">RIB_THICKNESS</code> /
                    2*<code class = "ph codeph">RIB_DISTANCE</code>. In addition, The recommendation is to use
                  nonfrozen design elements only in the <code class = "ph codeph">ELEMENT_GROUP</code>.</span></td></tr></table>

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</li>
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<article class = "topic task nested1" aria-labelledby = "ariaid-title3" id = "tso-c-user-TopOpt-DesArea-Rib_example">
<p><map name = "FPMap1"><area href = "#hj-top" title = "Back to Top" shape = "rect" coords = "416, 0, 435, 10"/></map><span class = "itemsprite"/></p><h2 class = "title topictitle2">Example: Rib Definition</h2>

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<section><div class = "li step p">
The following figure shows the rib restriction for a given distance (size of green circle) and
            given thickness (blue circle). The defined rib direction is out-of-plane of the image.
            The outer layer of the elements is not used in the defined rib restriction. <br/><img class = "image" src = "../TsoUserImages/topoDvconRibExample2.png" width = "600"/><br/>
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