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mgaafar
Posts: 107
Registered: ‎11-29-2011
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Nonlinear analysis Iteration

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03-26-2012 08:05 AM

Hello,

        I created a model for a slab on grade with compression only soil condition which will trigger the nonlinear analysis engine. the default parameters for the number of  laod increments and iterations were 25 but I did not get convergance So I increased the iterations and load increments to 40, but the problem during analysis it still uses the 25 and not the 40, I tried to do something similar on a small model and I found that it is kind of a bug that the input file does not get updated if I change the incremental method parameters. how can I overcome this issue without having to recreate the model from scratch with the proper parameters.

Thanks

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pp2008
Posts: 494
Registered: ‎06-23-2008

Re: Nonlinear analysis Iteration

03-26-2012 09:15 AM in reply to: mgaafar

The setting in Job Preferences is only the default setting for new load cases.

For the existing load case it can be set individually selecting appropriate load case and using Parameters button:

nonlin1.png

It can be also set for the list of load cases specifying the list and using Set parameters:nonlin2.png

 

In case of convergence problems it may be more efficient to use full Newton-Raphson method ("Matrix update after each iteration" active) instead of increasing maximum number of iterations in increment.

 

If  for model with uplift supports the convergence problems are observed during the last load increment in some load case there is a big chance that structure is unstable for these loads - like overturning of the structure.

 

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Regards,



Pawel Pulak
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