.. function:: uniaxialMaterial('ImpactMaterial', matTag, K1, K2, sigy, gap)
:noindex:
This command is used to construct an impact material object
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``matTag`` |int| integer tag identifying material
``K1`` |float| initial stiffness
``K2`` |float| secondary stiffness
``sigy`` |float| yield displacement
``gap`` |float| initial gap
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.. seealso::
`Notes <http://opensees.berkeley.edu/wiki/index.php/Impact_Material>`_