Normal forces & multiple LCs in Analyze ThII

Dear experts,

If I understood well here , the Analyze ThII component uses the highest normal force from all Load Cases to account for the geometric stiffness 2nd order effects.

I’m sorry, but I really do not understand why there it is said:

“The advantage is, that in the presence of several load-cases one can chose for each element the largest compressive force as NII. This gives a lower limit for the structure’s stiffness. A re-evaluation of the load-cases using these NII values leads to a structural response which is too soft. However the different load-cases may then be safely superimposed.”

Shouldn’t the Analyze ThII component use the normal force of each LC to compute the displacements and stresses for each corresponding LC? Is there a way to do so?

Thank you very much in advance!

Dear @Vigardo,
at the moment, the input-plug ‘LCase’ at the ‘Analyze ThII’-component can be used to specify the load-case from which to use N as NII. If ‘-1’ is provided (the default) then the largest compressive force of all load-cases is chosen.
If one wants to calculate second order theory responses for each load-case separately, it is necessary to do multiple calculations with corresponding ‘LCase’-input.
This will change, when load-case combinations available.
– Clemens

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Great news! I’ll be happy to use your load-case combinations as soon as they become available :slight_smile:

I’m sorry but I have one more question about Th.II:

By default OptiCroSec component uses Th.I. How would I include Th.II effects during cross-secrion optimization? It suffices to connect Analyze ThII Model output to the corresponding input of OptiCroSec?

Thanks Clemens for the quick response and your patience!

Hi @Vigardo,
currently OptiCroSec makes use of the existing NII values of the elements (same as ‘Analyze’). However currently (version 2.2.0) it does not update them when changing the cross sections.
– Clemens

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