Convergence issue using Concrete02

[KhaledSaif]

Hello guys,
I had a convergence issue when I used Concrete02 material in a gravity load analysis. However, when I changed it to Concrete01 (no tension strength for concrete) it worked just fine. Any idea why this happened? Thanks

Here is the code:

# MATERIAL parameters
# confinded concrete
set fpc [exp -23*$MPa]; # Concrete compressive strength at 28 days
set Epsc0 0.003; # concrete strain at maximum strength
set E0 [exp (2*$fpc)/$Epsc0]; # initial slope for the compressive stress–strain curve
set fpcu [exp 0.4*$fpc]; # concrete crushing strength. MPa
set Epsu -0.01; # concrete strain at crushing strength
set ften [exp 0.7*(-$fpc**0.5)]; # tensile strength of the concrete, MPa
set Ets [exp $ften/0.002]; # tension softening stiffness
set Lambda 0.1; # the ratio between unloading slope and initial slope
# unconfinded concrete
set fupc [exp -23*$MPa]; # Concrete compressive strength at 28 days
set Eupsc0 -0.003; # concrete strain at maximum strength
set Eu0 [exp (2*$fupc)/$Eupsc0]; # initial slope for the compressive stress–strain curve
set fupcu [exp 0.0*$fupc]; # concrete crushing strength. MPa
set Eupsu 0.005; # concrete strain at crushing strength

#uniaxialMaterial Concrete02 $matTag $fpc $epsc0 $fpcu $epsU $lambda $ft $Ets
uniaxialMaterial Concrete02 1 $fpc $Epsc0 $fpcu $Epsu $Lambda $ften $Ets; #Confined Conc.
uniaxialMaterial Concrete02 2 $fupc $Eupsc0 $fupcu $Eupsu $Lambda $ften $Ets; #Uncon Conc.

[alperozturk]

Your strain at maximum strength seems to be a positive value. For compressive parameters regarding concrete we use negative values.
set Epsc0 -0.003; # concrete strain at maximum strength
set Eupsu -0.005; # concrete strain at crushing strength
this might solve your convergence problem.

ao

[KhaledSaif]

Thanks Alperozturk,
but "Compressive concrete parameters should be input as negative values (if input as positive, they will be converted to negative internally)."