From my understanding, the Buckling Modes and Optimise Cross Section functions by Karamba 3D are based off of EC3 for steel structures.
I am hoping to calculate the flexural and lateral torsional buckling for aluminium joinery elements. The intent is to then output the optimised cross section from a predetermined family of joinery sections. Are the Buckling Modes functions able to adjust methods for aluminium components if the material properties are defined (following procedures in EC9)? Or will it always treat the elements as if it were steel?
Would appreciate any help on this, or information on if there is another method better suited to aluminium components.
Hi @Braeden1275,
the buckling modes calculation in Karamba3D is based on the stiffness and geometric stiffness of the structure and is not linked to any building code.
The cross section optimization and utilization-calculations are based on EC3. There buckling is taken into account via a predefined buckling length in local Y- and Z- direction as well as for lateral torsional buckling (see here for more information).
Currently (version 3.1.50129) Karamba3D applies the EC3 procedure for all types of materials. There is not yet a EC9 option. When using proper strength values for the aluminum the error in applying EC3 procedures should not be very large.
– Clemens
Thank you for your response and helpful information. For now, I am happy to ignore the cross section optimisation feature. I appreciate that the differences may be minimal between EC3 and EC9 but I am more curious about the buckling results.
I do have another question regarding the Buckling Modes function. I have a script which can successfully calculate the buckling modes for a simply-supported beam orientated in the z-direction when there is a compressive axial load applied to the top of the beam (the top restraint allows movement in the z-direction to simulate a slotted mullion connection - top image). However, when I relocate the point load so that it acts transversely (in the x or y-direction - bottom image), the Buckling Modes function does not produce any output as there are no second-moment forces. I have attempted to input voluntary buckling lengths and Ig values in the Modify Element function to no avail. Is the buckling Modes function able to calculate the lateral torsional buckling modes for a simply supported beam?
Hi @Braeden1275,
Currently, lateral-torsional buckling is only accounted for in the EC3 code calculations. The buckling mode analysis in Karamba3D 3.1.5 does not include lateral-torsional buckling, as the beam elements have no warping degree of freedom.
For the buckling modes component to function, NII normal forces must be defined—either through beam modification or by performing calculations according to second-order theory. Without these, the geometric stiffness matrix does not exist.
– Clemens
