Hi,
I've been working on the model of a portal frame, and I had set up my bracings as tension-compression members, so it's being calculated as a nonlinear analysis. I am coming across 'no convergence issues'. I tried a few things as outlined on this page but without success ("No convergence of nonlinear problem" during analysis in Robot Structural Analysis (autodesk.com)
Could someone help me to sort this issue please?
Solved! Go to Solution.
Solved by Krzysztof_Wasik. Go to Solution.
I have verified your model and have the following remarks.
- you have used compressed only members for bracings - used sectiopn types (angles) suggest that your intention was using tension only members for bracings (correct me if I have missed your idea). I would change bracings to tension only members.
-you are using default setting/parameters for nonlinear load cases. I would suggest activation Matrix update after each iteration setting as described in Non convergence.......-article
For bracings changed to tension only members and modified parameters of nonlinear cases model converges for all load cases.
Thanks for your reply. My mistake, I thought I had set them up as a tension bars.
Related to the parameters for the analysis, I added automatic calculations (manual calculations - generated) and I am getting the same convergence error. My question is, can I set up the parameters for nonlinear combinations as well? It would this interfere with the results?
You can set calculation parameters for arbitrary load case/combination number. Type all for all load cases in Case list
@Krzysztof_Wasik I had this settings as advised. I am having really high values for the bending moments in most of the combinations, not too sure why.
In my opinion there are too many releases defined in the model.
Verify displacements - especially for wind loads - they are unrealistic
for instance when supports for UY are defined in nodes 380 and 381 moments drops down
.
Try pinned supports in the right side in place of rollers
M. Agayr
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Yes, definitely there's some issues with the releases on these members. The problem is, I can't add supports where you suggested, this structure will be on top of rails to move north-south and will be lifted to ships when needed. I divided the column on the door frame in 3 parts, the beams below (marked in yellow) need to work as a cantilevers.
I have set up the releases like this and I still have higher displacements.
I attached the model, it is a bit hard to see on the snip.
Set members 31 32 45 47 as truss members (tension +compression)
This will reduce displacements.
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