Bidirectional Section

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This command allows the user to construct a Bidirectional section, which is a stress-resultant plasticity model of two coupled forces. The yield surface is circular and there is combined isotropic and kinematic hardening.

section Bidirectional $secTag $E $Fy $Hiso $Hkin

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$secTag	unique section tag
$E	elastic modulus
$Fy	yield force
$Hiso	isotropic hardening modulus
$Hkin	kinematic hardening modulus

NOTES:

• The bidirectional section is a suitable base isolator model and should be used in conjunction with a ZeroLengthSection element to this end.
• The implementation is a generalization of the uniaxial return map algorithm for rate independent plasticity (page 45, Simo and Hughes, 1998)

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Code Developed by: Michael H. Scott, Oregon State University