Reinforcing Steel Material

$matTag	integer tag identifying material
$matTag	unique material object integer tag
$fy	Yield stress in tension (see Figure 1)
$fu	Ultimate stress in tension
$Es	Initial elastic tangent
$Esh	Tangent at initial strain hardening
$esh	Strain corresponding to initial strain hardening
$eult	Strain at peak stress
-GABuck	Buckling Model Based on Gomes and Appleton (1997)
$lsr	Slenderness Ratio (see Figure 2)
$beta	Amplification factor for the buckled stress strain curve. (see Figure 3)
$r	Buckling reduction factor r can be a real number between [0.0 and 1.0] r=1.0 full reduction (no buckling) r=0.0 no reduction 0.0<r<1.0 linear interpolation between buckled and unbuckled curves
$gamma	Buckling constant (see Figures 3 and 4)