Hi.
I'm doing a non-linear analysis on a simple model with static loads from a seismic analysis (separate file) to determine necessary moment in my foundation slab. However, whenever I get negative reactions, that should result in uplift, i get "no convergence of nonlinear problem". Why does this happen?
See attached image of a corner of my basement, showing support conditions. There are core walls as well, supported in the same way as the column showed.
Solved! Go to Solution.
Solved by Artur.Kosakowski. Go to Solution.
add the self weight case as a starting case for the non linear load case
Please check if you defined the uplift in the correct direction (UZ+ or UZ-) as well as make sure that the overturning moment is smaller than the stabilizing one. If both are true then make sure that you marked both matrix updates in the parameters of nonlinear analysis.
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Rafael Medeiros
Robot Structural Analysis
Hello,
Similar problem with convergence. (i think)
I have a simple rectangular steel structure, with a lots of load cases.
For most of the cases, the results seem to be accurate, but for one (5 - Equipments) the results are totaly wrong.
Can anyone give me some advice, pls ? Why is this happening?
Please find model with results here http://www.filemail.com/d/chfrecyznfzhzdu
Thanks
To get the convergence for case 5 it is enough to change the relative tolerances from 1e-4 to 1e-3. On the other hand as the load increases there is the warning about the critical load which might have been actually exceeded. I think you should investigate this as well as the reason for instabilities (I have ignored them as my focus was on the convergence issue you indicated). Mind that if you want to combine this load with others you may actually be not interested in results obtained for case 5 alone as such situation does not happen in reality.
On more remark: I'm not sure what was your intention but you set that the first load case should be used as the starting case for case 1 - perhaps you should check that too.
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