Different Parameters for steel01 material

[tssunilkumar]

Dear Opensees Experts,

I have noticed in example 3 that the steel01 material is defined as follows:
As per this the various parameters for the definition are: My, EI and b


####################################################################################################
# COLUMN section
# calculated stiffness parameters
set EICol [expr $Ec*$IzCol]; # EI, for moment-curvature relationship
set EACol [expr $Ec*$ACol]; # EA, for axial-force-strain relationship
set MyCol [expr 130000*$kip*$in]; # yield moment
set PhiYCol [expr 0.65e-4/$in]; # yield curvature
set EIColCrack [expr $MyCol/$PhiYCol]; # cracked section inertia
set b 0.01 ; # strain-hardening ratio (ratio between post-yield tangent and initial elastic tangent)
uniaxialMaterial Steel01 $ColMatTagFlex $MyCol $EIColCrack $b; # bilinear behavior for flexure
uniaxialMaterial Elastic $ColMatTagAxial $EACol; # this is not used as a material, this is an axial-force-strain response
section Aggregator $ColSecTag $ColMatTagAxial P $ColMatTagFlex Mz; # combine axial and flexural behavior into one section (no P-M interaction here)
####################################################################################################


But, as per command manual the following should be the arguements for steel01 material: ie; Fy, E0 and b


####################################################################################################
uniaxialMaterial Steel01 $matTag $Fy $E0 $b <$a1 $a2 $a3 $a4>
$matTag integer tag identifying material

$Fy yield strength
$E0 initial elastic tangent
$b strain-hardening ratio (ratio between post-yield tangent and initial elastic tangent)
$a1 isotropic hardening parameter, increase of compression yield envelope as proportion of yield strength after a plastic strain of $a2*($Fy/E0). (optional)
$a2 isotropic hardening parameter (see explanation under $a1). (optional).
$a3 isotropic hardening parameter, increase of tension yield envelope as proportion of yield strength after a plastic strain of $a4*($Fy/E0). (optional)
$a4 isotropic hardening parameter (see explanation under $a3). (optional)
#####################################################################################################

Can someone explain why this difference?
Please excuse me if this is a stupid question. I am new in structural analysis and also in Opensees.

Regards,

Sunilkumar

[fmk]

no difference . .simply using the steel01 material to define a moment-rotation relationship for a hinge.