ZeroLengthImpact3D

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This command constructs a node-to-node zero-length contact element in 3D space.

element zeroLengthImpact3D $tag $slaveNode $masterNode $direction $initGap $frictionRatio $Kt $Kn $Kn2 $Delta_y $cohesion

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$tag	Unique element object tag
$slaveNode	Slave node tag
$masterNode	Master node tag
$direction	1 if normal vector of master plane points to +X direction 2 if normal vector of master plane points to +Y direction 3 if normal vector of master plane points to +Z direction
$initGap	Initial gap between master plane and slave plane
$frictionRatio	Friction ratio
$Kt	Penalty in tangential directions (parallel to master and slave planes)
$Kn	Penalty in normal direction (normal to master and slave planes)
$Kn2	Penalty in normal direction after yielding based on Hertz impact model
$Delta_y	Yield deformation based on Hertz impact model
$cohesion	Cohesion, if no cohesion, it is zero

NOTES:

1. This element has been developed on top of the “zeroLengthContact3D”. All the notes available in “zeroLengthContact3D” wiki page would apply to this element as well. It includes the definition of master and slave nodes, the number of degrees of freedom in the domain, etc.
2. This element adds the capabilities of “ImpactMaterial” to “zeroLengthContact3D”, without the need for extra nodes and elements in the modeling process. That is the capability of having an "initial gap" in the normal direction and also the capability of considering energy dissipation due to impact in the normal direction.
3. This element has been used to model the superstructure-abutment interaction in bridges at University of Connecticut (UConn) and University of Nevada, Reno (UNR). This element was found to be fast-converging and eliminating the need for many extra elements and nodes in the modeling process.

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EXAMPLE SCRIPT:

The following zip file contains an example script and the corresponding input cyclic displacement.

File:ExampleScript.zip

After running the example script, the following hysteresis loop is resulted in normal direction under cyclic excitation:

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REFERENCES:

http://opensees.berkeley.edu/wiki/index.php/ZeroLengthContact_Element

Muthukumar, S., and DesRoches, R. (2006). “A Hertz Contact Model with Non-linear Damping for Pounding Simulation.” Earthquake Engineering and Structural Dynamics, 35, 811-828.

Muthukumar, S. (2003). “A Contact Element Approach with Hysteresis Damping for the Analysis and Design of Pounding in Bridges.” PhD Thesis, Georgia Institute of Technology. http://smartech.gatech.edu/

Nielson, B. (2005). “Analytical Fragility Curves for Highway Bridges in Moderate Seismic Zones.” PhD Thesis, Georgia Institute of Technology. http://smartech.gatech.edu/

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Code Developed by: Arash E. Zaghi, Majid Cashany, University of Connecticut (UConn)