question about 2D soil modelling

[mahsashamsaei]

hi every body
i made soil profile in opensees
when active update stage 1 in gravity analysiss stoped analyze
who can help me?


thanks

[fmk]

did you follow the examples from UCSD?

[mahsashamsaei]

yes
i follow the example from opensees site
but when set dimention 200*100 show:
error not converge

[sb1966]

Does it converge without updating the material stage?
If it does not, then please check your model, particularly the BCs.

If you use InitialState Wrapper material, take care that you use the material tag corresponding to the initialState Wrapper and not the tag for original nDMaterial, while updating the material stage.

[mahsashamsaei]

thank you for your answering
i use nd material when i analyzed stage 0 and dynamic analyze, converges
can i ignore update stage 1 or ignore gravity analyze?

i have another question
i model pipe line with nonlinear beam column with unixial material steel 02
when i analyze model with pilpe line and with out pipe line output strain in elements of soil that is In the vicinity of the pipeline is equal
I think the pipe did not affect the hardness of the soil in that area

The soil and pipe connection was performed with equal dof

[sb1966]

mahsashamsaei wrote:
> thank you for your answering
> i use nd material when i analyzed stage 0 and dynamic analyze, converges
> can i ignore update stage 1 or ignore gravity analyze?
>
> i have another question
> i model pipe line with nonlinear beam column with unixial material steel 02
> when i analyze model with pilpe line and with out pipe line output strain in elements
> of soil that is In the vicinity of the pipeline is equal
> I think the pipe did not affect the hardness of the soil in that area
>
> The soil and pipe connection was performed with equal dof

Hi,

1. As it converges in elastic stage, model seems to be OK
2. Ignoring plastic analysis (material stage 1) will mean linear analysis only. You should decide whether it is appropriate or not, depending on your objectives of analysis.
3. Usually gravity analysis is done using elastic material (material-stage 0. See examples in wiki page) and then, before starting the dynamic analysis, material stage is updated.
4. It seems to me now that i) you may try to increase the number of analysis steps by reducing the dT in analysis. ii) You may also try to change the solution algorithm, iii) systems, and/or iv) increase maximum number of trials in a time step before convergence is achieved. Refer to command manual for these.

In nonlinear dynamic analysis, you need to try different combinations of these parameters to achieve convergence, and it is quite normal to have non-convergence in the first few trial analyses. Unfortunately such combinations depend on the model at hand and no general prescriptions can be made. One needs to learn from previous experience only.

It is better to open a logFile by using logFile command and check if the analysis converges at every time step or not.
I do not know about your dynamic load pattern (is it a load, or UniformExcitation, multiSupport Excitation etc.) So it is difficult to comment. Usually, if you are using recorded ground motion file then the time steps should not be an issue and you can try varying other parameters mentioned above.
Hope it helps. BTW, sorry for my delayed response.

Reg your pipe model more details are necessary to comment. However, due to equalDOF constraint, it is natural to have deformations in soil near the pipe same as that of the pipe.

Thanks and Best Wishes.