Axial LimitCurve

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This command is used to construct an axial limit curve object that is used to define the point of axial failure for a LimitStateMaterial object. Point of axial failure based on model from Chapter 3 of PEER 2003/01 report. After axial failure the response of LimitStateMaterial is forced to follow axial limit curve.

limitCurve Axial $curveTag $eleTag $Fsw $Kdeg $Fres $defType $forType <$ndI $ndJ $dof $perpDirn $delta>

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$curveTag	unique LimitCurve tag
$eleTag	integer element tag for the associated beam-column element
$Fsw	floating point value describing the amount of transverse reinforcement <math>(F_{sw} = \frac{A_{st}f_{yt}d_c}{s})</math>
$Kdeg	floating point value for the slope of the third branch in the post-failure backbone, assumed to be negative (see Figure 4-6)
$Fres	floating point value for the residual force capacity of the post-failure backbone (see Figure 4-6)
$defType	integer flag for type of deformation defining the abscissa of the limit curve 1 = maximum beam-column chord rotations 2 = drift based on displacment of nodes ndI and ndJ
$forType	nteger flag for type of force defining the ordinate of the limit curve. See NOTES 1. 0 = force in associated limit state material 1 = shear in beam-column element 2 = axial load in beam-column element
$ndI	nteger node tag for the first associated node (normally node I of $eleTag beam-column element)
$ndJ	integer node tag for the second associated node (normally node J of $eleTag beam-column element)
$dof	nodal degree of freedom to monitor for drift. See NOTES 2
$perpDirn	perpendicular global direction from which length is determined to compute drift. See Notes 2.
$delta	drift (floating point value) used to shift axial limit curve

NOTES:

1. Options 1 and 2 assume no member loads
2. 1 = X, 2 = Y, 3 = Z

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EXAMPLE:

<tcl>CenterColAxialSpring.tcl</tcl>

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DESCRIPTION:

Modeling Failures in Existing Reinforced Concrete Columns by Ken Elwood: File:ElwoodCJCE2004.pdf

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REFERENCES:

Elwood, K.J and Moehle, J.P., "Shake Table Tests and Analystical Studies on the Gravity Load Collapse of Reinforced Concrete Frames", Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA. PEER 2003/01.

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Code Developed by: Ken Elwood, University of British Columbia