CoupledZeroLength Element

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This command is used to construct a CoupledZeroLength element object, which is defined by two nodes at the same location. The nodes are connected a single UniaxialMaterial element to represent the force-deformation relationship for the element in a 2d plane. Unlike a ZeroLength element which can only provide a rectangular force interaction surface in a 2d plane, this element provides a circular force interaction surface.

element CoupledZeroLength $eleTag $iNode $jNode $dirn1 $dirn2 $matTag <$rFlag>

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$eleTag	unique element object tag
$iNode $jNode	end nodes
$matTag	tags associated with previously-defined UniaxialMaterial
$dir1 $dir2	the two directions, 1 through ndof.
$rFlag	optional, default = 0
	rFlag = 0 NO RAYLEIGH DAMPING (default)
	rFlag = 1 include rayleigh damping

NOTE:

The valid queries to a zero-length element when creating an ElementRecorder object are 'force,' and 'material matArg1 matArg2 ...'

EXAMPLE:

element CoupledZeroLength 1 2 4 5 6 7; # truss tag 1 between nodes 2 and 4 acting in directions 5 and 6 with material 7.

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THEORY:

if change in element end displacements for 2 dof of interest are d1 and d2:

the deformation (strain in uniaxial material) of the material is set to be:

<math>\epsilon = sqrt( \delta 1^2 + \delta 2^2)</math>

and if resulting force (stress from uniaxial material) is Sigma then the force computed for the two directions 1 and 2 are:

<math> F_1 = (\Sigma * \delta 1) / \epsilon </math> <math> F_2 = (\Sigma * \delta 2) / \epsilon </math>

NOTE: in case where <math>\epsilon = 0.0</math>, the forces are computed using <math>\Sigma</math> and the last committed set of displacements that were not zero.

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Code Developed by: fmk