No-linear model with rotational spring

[mariantonietta2]

Dr F. Mc Kenna,

I am so sorry to bother you again for another problem.

I built a model of simple supported beam with a zeroLength Element inside that model a rotazional spring. I imposed only a gravity load to perform the static analysis, but my model is very non-linear (the spring has a very low stiffness) so Opensees give me a convergence error.
The analysis objects that I used (and give me a smaller convergence error of other analysis objects that I found) are:


constraints Transformation;
numberer RCM;
system SparseGeneral;
test NormDispIncr 1. e-4 25 5;
algorithm ModifiedNewton
integrator LoadControl 1
analysis Static
analyze 1

and the error that I obtained is

WARNING: CTestNormDispIncr::test() - failed to converge but going on - current Norm: 0.000206899 (max: 1e-005, Norm deltaR: 6962.91)

How could I avoid this convergence problem for a very non-linear system?

(I consulted the examples on-line and in the manual, but there are not examples of structure with a rotational spring inside)


I had another question:
inside the code I use the command

element elasticBeamColumn 6 11 13 $A $E $I 1

in order to build the element and Opensees give me another error in the model without the rotational spring too:

expected integer but got "-type"

but it seems that this error doesn't influence the solution. Does this error line influence the solution?

Thank you for your time

Regards
M

[carlos]

Hello,

if there is a non linear problem, I would suggest you to apply the load in several steps changing for example

integrator LoadControl 0.1

analyze 10

The other possibility is that the system it is not stable.

For me the other question is a little bit surprissing as it should stop the analysis as the element is not created. I would check carefully the model and results as also the warning (maximum 1e-5) it is not related with the test you have used:

test NormDispIncr 1. e-4 25 5;

Hope this helps

[mariantonietta2]

Thank you Carlos,

I tried and it works.

M