What is mu in Hysteretic Material?

macropaine · Post by **macropaine** » Tue Jul 28, 2009 8:16 am

Dr. Silvia,
In the manual, it is referred to "the degraded unloading stiffness based on ductility, mu" about hysteretic material. Is "mu" the ductility of section curvature?
In addition, it is also referred the degraded unloading stiffness equals to pow($mu,-$beta)*k0, so the unloading stiffness is k0 if beta is 0. But when I plot the force-deformation curve, "set beta 0", the stiffness of the branch after e3p is zero, i.e. the slope is flat. could you please tell me how to determine the degraded unloading stiffness?
Thanks a lot!

silvia · Post by **silvia** » Tue Jul 28, 2009 8:24 am

mu is the ratio of the current strain value to the first yield strain defined in the material.
yes, the unloading stiffness is k0 if beta is zero -- but k0 is the initial elastic stiffness of the material, not the current tangent stiffness.

macropaine · Post by **macropaine** » Wed Jul 29, 2009 3:08 am

uniaxialMaterial Hysteretic 100 62.95 0.0025 79 0.015 23.7 0.026 -62.95 -0.0025 -79 -0.015 -23.7 -0.026 0.5 0.5 0 0 0
The slope after e3p point, "23.7", is 0, not k0. k0 should equal 62.95/0.0025.
Why?
thanks

silvia · Post by **silvia** » Wed Jul 29, 2009 6:44 am

yes, after the third point it is zero, that is how the model is defined.
the unloading stiffness is another thing, the unloading stiffness comes into play when you reversed the loading direction.

macropaine · Post by **macropaine** » Wed Jul 29, 2009 8:03 am

Thank you, Silvia. I have confused the loading and unloading. Now it is clear.

macropaine · Post by **macropaine** » Wed Jul 29, 2009 8:04 am

It is noticed there are 10 figures (run1 to run10) to demonstrate the behavior of hysteretic material in the chm user manual.
1. could you please explain how to set the pinch or damage parameters for obtaining the origin-oriented behavior, such as run7 and run8?
2. what does the damage parameter mean?
3. what is Eii in "D2(Eii/Eult)" for $damage2?

silvia · Post by **silvia** » Wed Jul 29, 2009 8:29 am

look at the on-line manual, it has a description of the paramters.
the only difference between the different runs is the loading history, also described in the manual.
the E, i beleive, is the hysteretic energy for each cycle -- you'd have to look at the code to understand it in more detail.

macropaine · Post by **macropaine** » Wed Jul 29, 2009 11:41 pm

I am looking at the online manual. Thank you.