InitialStateAnalysisWrapper

This command is used to construct an InitialStateAnalysisWrapper nDMaterial object.

nDMaterial InitialStateAnalysisWrapper $matTag $nDMatTag
        $nDim

`eleTag`	unique integer tag identifying nDMaterial object
`nDMatTag`	the tag of the associated nDMaterial object
`nDim`	number of dimensions (2 for 2D, 3 for 3D)

The InitialStateAnalysisWrapper nDMaterial allows for the use of the InitialStateAnalysis command for setting initial conditions. The InitialStateAnalysisWrapper can be used with any nDMaterial. This material wrapper allows for the development of an initial stress field while maintaining the original geometry of the problem. An example analysis is provided below to demonstrate the use of this material wrapper object.

NOTES:

There are no valid recorder queries for the InitialStateAnalysisWrapper.
The InitialStateAnalysis off command removes all previously defined recorders. Two sets of recorders are needed if the results before and after this command are desired. See the example below for more.
The InitialStateAnalysisWrapper material is somewhat tricky to use in dynamic analysis. Sometimes setting the displacement to zero appears to be interpreted as an initial displacement in subsequent steps, resulting in undesirable vibrations.

EXAMPLES:

InitialStateAnalysisWrapper definition with material tag 1, and associated nDMaterial tag 2 for a 2D analysis

nDMaterial InitialStateAnalysisWrapper 1 2 2

Code Developed by: Chris McGann, Pedro Arduino, & Peter Mackenzie-Helnwein, at the University of Washington

EXAMPLE ANALYSIS:

The example input file below demonstrates an how the InitialStateAnalysis command can be used with the InitialStateAnalysisWrapper to generate a gravitational state of stress in a single element. As shown below, the use of the InitialStateAnalysis command necessitates the use of two sets of recorders, one to record results during the initial state analysis, and one for all subsequent steps. It is not required to record results during the initial state analysis, but the example below includes this data to demonstrate the effect of the InitialStateAnalysis command. At the end of the analysis, there should be non-zero stress and strain in the element with zero displacement.

 wipe</p>
<p>model BasicBuilder -ndm 3 -ndf 3</p>
<ol>
<li>create the nodes</li>
</ol>
<p>node 1 1.0 0.0 0.0 node 2 1.0 1.0 0.0 node 3 0.0 1.0 0.0 node 4 0.0
0.0 0.0 node 5 1.0 0.0 1.0 node 6 1.0 1.0 1.0 node 7 0.0 1.0 1.0 node 8
0.0 0.0 1.0</p>
<ol>
<li>boundary conditions</li>
</ol>
<p>fix 1 1 1 1 fix 2 1 1 1 fix 3 1 1 1 fix 4 1 1 1 fix 5 1 1 0 fix 6 1 1
0 fix 7 1 1 0 fix 8 1 1 0</p>
<ol>
<li>define main material obeject</li>
</ol>
<p>nDMaterial ElasticIsotropic 1 25000 0.35</p>
<ol>
<li>define material wrapper</li>
</ol>
<p>nDMaterial InitialStateAnalysisWrapper 2 1 3</p>
<ol>
<li>create the element (NOTE: the material tag associated with this
element is that of the wrapper)</li>
</ol>
<p>element SSPbrick 1 1 2 3 4 5 6 7 8 2 0.0 0.0 -17.0</p>
<ol>
<li>create the pre-gravity recorders</li>
</ol>
<p>set step 0.1</p>
<p>recorder Node -time -file Gdisp.out -dT $step -nodeRange 5 8 -dof 1 2
3 disp recorder Element -ele 1 -time -file Gstress.out -dT $step stress
recorder Element -ele 1 -time -file Gstrain.out -dT $step strain</p>
<ol>
<li>create the gravity analysis</li>
</ol>
<p>integrator LoadControl 0.5 numberer RCM system SparseGeneral
constraints Transformation test NormDispIncr 1e-5 40 1 algorithm Newton
analysis Static</p>
<ol>
<li>turn on the initial state analysis feature</li>
</ol>
<p>InitialStateAnalysis on</p>
<ol>
<li>analyze four steps</li>
</ol>
<p>analyze 4</p>
<ol>
<li>turn off the initial state analysis feature</li>
</ol>
<p>InitialStateAnalysis off</p>
<ol>
<li>create post-gravity recorders</li>
</ol>
<p>recorder Node -time -file disp.out -dT $step -nodeRange 5 8 -dof 1 2
3 disp recorder Element -ele 1 -time -file stress.out -dT $step stress
recorder Element -ele 1 -time -file strain.out -dT $step strain</p>
<ol>
<li>analyze for three steps, should have non-zero stress and strain with
zero displacement</li>
</ol>
<p>analyze 3</p>
<p>wipe