Are there any OpenSees material models that allow definition of initial stress? Other than intial stress, only simple elastic-plastic yielding is required.
Any ideas?
Thanks
Steve
Initial Stress
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sbuonopane
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Initial Stress
Stephen Buonopane
Dept. of Civil Engineering
Bucknell Univ.
Lewisburg, PA 17837
Dept. of Civil Engineering
Bucknell Univ.
Lewisburg, PA 17837
initial stress definition
Actually there are...
Set of models that one can define through Template 3D EP (vonMises, CamClay, DruckerPrager, MohrCoulomb, LeonParabolic,... or any combination of those in terms of yield function and plastic potential function, and combinations with no hardening/softening, scalar (isotropic) and kinematic (translational and rotational) hardening and softening (both linear and nonlinear) allow you to define initial stress.
One has to be carefull as intial stress will throw the global equilibrium iterator in panic but with wise external loading or small amounts of initial stress this is not a problem, full Newton global iterator is powerfull enough to do it for you, in combination with one of the hyperspherical constraints (arc length ...).
We do it all the time, as most soil models cannot have zero state of stress so we add a bit of hydrostatic confinment just to make it work in the first step. Since the first stage of loading is usually self weight, this initial state of stress just grows toward higher confinments so everything is just fine. This needs to be done as for example DruckerPrager (having apex at stress origin) really behaves funy at stress origin...
Boris
Set of models that one can define through Template 3D EP (vonMises, CamClay, DruckerPrager, MohrCoulomb, LeonParabolic,... or any combination of those in terms of yield function and plastic potential function, and combinations with no hardening/softening, scalar (isotropic) and kinematic (translational and rotational) hardening and softening (both linear and nonlinear) allow you to define initial stress.
One has to be carefull as intial stress will throw the global equilibrium iterator in panic but with wise external loading or small amounts of initial stress this is not a problem, full Newton global iterator is powerfull enough to do it for you, in combination with one of the hyperspherical constraints (arc length ...).
We do it all the time, as most soil models cannot have zero state of stress so we add a bit of hydrostatic confinment just to make it work in the first step. Since the first stage of loading is usually self weight, this initial state of stress just grows toward higher confinments so everything is just fine. This needs to be done as for example DruckerPrager (having apex at stress origin) really behaves funy at stress origin...
Boris