Does the “Optimize Cross Section (Karamba3D)” component take into account the verification of non-buckling of bars according to the buckling lengths entered in each part according to the second order theory in the same way as the component "AnalyzeThII ( Karamba3D) "?
The algorithm behind ‘Optimize Cross Section’ relies on the design procedure of Eurocode 3. In order to get sound results out of this, the buckling length of the members need to be set correctly.
The ‘AnalyzeThII’-component calculates the geometric stiffness which contains the effects of axial or in-plane forces on the system stiffness. It does not consider the bars buckling length.
If I understand correctly to summarize, we must use the two components in succession, first the component “AnalyzeThII” to inform for each bar the critical axial force depending on the rigidity of each bar then the component “Optimize Cross Section” to check the model taking into account the buckling lengths? Is it this ?
Is it possible to know the slenderness of the bars ?
In case the buckling length of an element can not be determined based on its boundary conditions, one needs to use the ‘BucklingModes’-component: The buckling length results as the distance between the inflection points of the first buckling mode. Use the ‘ModifyElement’-component to inform the corresponding elements.
Karamba3D 1.3.3 uses an approximate procedure for determining the default values of the element’s buckling lengths (see here). In case of system buckling this is not on the safe side and the design procedure according to EC3 thus gives wrong results in such instances.