I am analysing at the moment a complex grid shell that would require non-linear analysis. When trying to use this command the three numerical methods available stop iterating after lambda 0.24, even when increasing the load steps to 100.
The model is quite large, it has 12707 elements and 4520 nodes, is it possible that the model is too large to converge? I understand that this command is still a WIP and may not be able to analyse very large non-linear structures.
Linear analysis in the structure works, it just does not give accurate enough values for the forces in the members. Non-linear analysis Info.txt (15.0 KB)
it is hard to say why the calculation does not converge.
Do you really need a non-geometric analysis for your grid shell or might be a second order theory (ThII) calculation sufficient? The difference between those is, that the former includes the in-plane deformation caused by transverse displacements. This usually affects the results only in case the displacements are large with respect to the cross section size.
Effects like buckling, increase of transverse displacements due to in-plane compression forces and decrease of displacements caused by tension forces are covered by ThII analysis as well and can be calculated more efficiently in that way.
– Clemens
Thank you for your message and sorry for the late reply. My suspicion is that the non-linear analysis was not converging because the loads were too high and therefore the system would buckle.
Now with the loads reduced, I have been trying both Second order theory analysis and non-linear analysis, however the results differ considerably. I get that according to second order theory the structure buckles with a load factor of 0.2 whilst Non linear suggests buckling does not occur and gives a load factor of 2.0.
Would you be able to say why the algorithms differ so much in their buckling calculations?
