Shell Element

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This command is used to construct a ShellMITC4 element object, which uses a bilinear isoparametric formulation in combination with a modified shear interpolation to improve thin-plate bending performance.

element ShellMITC4 $eleTag $iNode $jNode $kNode $lNode $secTag

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$eleTag	unique element object tag
$iNode $jNode $kNode $lNode	four nodes defining element boundaries, input in counter-clockwise order around the element.
$secTag	tag associated with previously-defined SectionForceDeformation object. Currently must be either a PlateFiberSection, or ElasticMembranePlateSection

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NOTE:

1. 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.
2. It is a 3D element with 6 dofs and CAN NOT be used in 2D domain.

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EXAMPLE:

set t 100.0
model basic -ndm 3 -ndf 6
nDMaterial ElasticIsotropic 1 200000 0.3
nDMaterial PlateFiber 4 1
set secArgs "7"
section PlateFiber $secArgs 4 $t
set EleType ShellMITC4
block2D $n1 $n2 1 1 $EleType $secArgs {
    1   0.0   0.0  0.0
    2   0.0    10  0.0
    3  1000    10  0.0
    4  1000   0.0  0.0
} 

REFERENCES:

Dvorkin,Bathe, A continuum mechanics based four node shell element for general nonlinear analysis, Eng.Comput.,1,77-88,1984

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Original implementation: Ed Love