Problem about the Bilin material

[lkang6]

Hi,
I have a problem with the Bilin material.
I use Bilin material for a spring with deterioration parameter set as following(refer to Lignos and Krawinkler ):
LS 130.0; # basic strength deterioration (
LK 130.0; # unloading stiffness deterioration
LA 1000.0; # accelerated reloading stiffness deterioration (a very large # = no cyclic deterioration)
LD 130.0; # post-capping strength deterioration
cS 1.0; # exponent for basic strength deterioration (c = 1.0 for no deterioration)
cK 1.0; # exponent for unloading stiffness deterioration (c = 1.0 for no deterioration)
cA 1.0; # exponent for accelerated reloading stiffness deterioration (c = 1.0 for no deterioration)
cD 1.0; # exponent for post-capping strength deterioration (c = 1.0 for no deterioration)
DP 1.0; # rate of cyclic deterioration for pos loading
DN 1.0; # rate of cyclic deterioration for neg loading

When I plot the force-displacement curve for this spring, there is no hysteretic loop. And then I tried other value for the paramaters, there is no hysteretic loop for the force-displacment. Are the parameters I set wrong? How should I set them? Please help me!!

Thank you so much!