failed to get compatible element forces and deformations

[murray710]

I had some quick questions regarding the exact cause of the error message "failed to get compatible element forces and deformations", when using forceBeamColumn elements throughout a building model. I understand that this essentially signifies a loss of convergence, but in the model I am using currently, my solution is an explicit formulation (alphaOS), so there is no convergence check at the global level. My global model cannot lose convergence, as it is never checked.

This must mean something happens within the elements to cause the problem. But the way I have understood forceBeamColumns from the manual, unless you trigger the '-iter' command, the element solution is also non-iterative, so how can convergence be lost? Is there any way to force the internal element solution to become an explicit procedure (regardless of inaccuracies it would produce), such that this error message would be avoided and analysis could continue? Or is that mathematically not possible?

Lastly, in the case that this error message DOES appear, is the model essentially 'dead', or is it possible to play with parameters and get it to continue? My understanding is that when this message is printed, the global DOF movements have already been committed, so it is not possible to try a smaller step size or anything to help the model proceed.

Thanks for the help.

[fmk]

no the element does iterate.

it's not dead, you can go back to the last step and try something different (if it fails in newstep (prediction step) your only option is to decrease the time step or try a different integrator), as you have no correction steps you can't do anything with the solution algorithm).

[seyedalirezajalali]

Hi Frank.
Thanks for your answer. Is what you mentioned correct for all types of analyses or just for the one being questioned in above post?
What do you exactly mean by "correction step"?