Pore Pressure Ratio Monitoring ?

[bayram_aygun]

Hi,
I have been trying to understand Example 15 in <http://cyclic.ucsd.edu/opensees >. There are only two materials in this code, namely:

nDMaterial PressureDependMultiYield 2 --------
nDMaterial FluidSolidPorous 1 --------

1) So what is "material 3" in the recorder lines below? I can understand that we can
measure pore pressure in materal 1 (FluidSolidPorous) but why material 3? Lastly, can we record anything from PDMY?

recorder Element -ele 1 -time -file stress1.out -dT 0.01 material 1 stress
recorder Element -ele 1 -time -file strain1.out -dT 0.01 material 1 strain
recorder Element -ele 1 -time -file stress3.out -dT 0.01 material 3 stress
recorder Element -ele 1 -time -file strain3.out -dT 0.01 material 3 strain
recorder Element -ele 1 -time -file press1.out -dT 0.01 material 1 pressure
recorder Element -ele 1 -time -file press3.out -dT 0.01 material 3 pressure

Can you direct me to any reference code or example where temporal ru is monitored in
addition to instantaneous ru along the depth of a soil column (e.g. ru-elevation curve at
t=5 sec, also in the attachment)?

I really appreciate your help,

[bayram_aygun]

Below you will see my recent understanding of the pore pressure issue, it could be wrong but I urge you to go into that and correct me if I'm telling you something wrong:


recorder Element -ele 1 -time -file press3.out -dT 0.01 material 3 pressure

This recorder command line monitors the pore pressure ratio (PPR) of quad (FourNodeQuad) soil element with tag 1. Dr. Elgamal thinks that "material 3" in the recorder is referring to integration point No. 3
within the element (there are 4 integration points in the quad 4 node
element). Integration point 1 is closest to the first node you define in
the element connectivity, and so forth for integration points 2 to 4.

Once you get your recorder file - "press3.out"- in this case, you will get three columns: 1st is the time step column, 2nd is the pore pressure column and the third is the PPR column. PPR is an indicator of how the water build-up evolves in time.

[bayram_aygun]

Hi everybody,

I'm trying to validate my OpenSees soil column model with Cyclic1D (<http://cyclic.ucsd.edu/>) but I'm getting inconsistent results. To be more clear, pore pressure ratios in clay layer are similar whereas loose sand pore pressure ratios are different. Cyclic1D shows that my soil layer liquefies (ru=1) where as my OpenSees recorder outputs show that there is no liquefaction (ru=0). I use this command line to get the pore pressure ratios:

recorder Element -ele 1 -time -file press1.out -dT 0.01 material 1 pressure

I heard that OpenSees can sometimes miscalculate pore pressures. Did anyone have a similar experience like mine?

Lastly, how can monitor vertical stresses in my quad elements? I want to try to calculate the pore pressure ratios by the formula to cross check what OpenSees does.

Thanks for your help,

[rjaeger]

Hi everybody,

I'm trying to validate my OpenSees soil column model with Cyclic1D (<http://cyclic.ucsd.edu/>) but I'm getting inconsistent results. To be more clear, pore pressure ratios in clay layer are similar whereas loose sand pore pressure ratios are different. Cyclic1D shows that my soil layer liquefies (ru=1) where as my OpenSees recorder outputs show that there is no liquefaction (ru=0). I use this command line to get the pore pressure ratios:

recorder Element -ele 1 -time -file press1.out -dT 0.01 material 1 pressure

I heard that OpenSees can sometimes miscalculate pore pressures. Did anyone have a similar experience like mine?

Lastly, how can monitor vertical stresses in my quad elements? I want to try to calculate the pore pressure ratios by the formula to cross check what OpenSees does.

Thanks for your help,

Hi Bayram,

I may sound like a broken record but you should really try getting into the source code. Frank and the other developers have done a nice job at keeping things clear and readable in the code. By looking at the code, you can personally evaluate the calculation routines and develop your own as well. I know you've been having issues for a few months now and it doesn't seem like your problems have been solved yet. So you should take this into consideration - it could save you time.

Robbie