Karamba Crossection optimisation and load combinations


I am trying to find a workaround to the lack of load combination in karamba while using the crossection optimisation but i am not sure about few things, I have two options so far:

  1. Use the LCfactor in the model viewer, feed different load combination and “browse” through them to find the worst case.
  • Does the crossection optimisation component is done on a model with the LCfactors applied or without?
  • Is there an already coded way to envelop the crossection optimisation when browsing through the different Load combinations, in order to find the biggest crossection? (Worst case scenario)
  1. Creating one karamba load case per load combination and feed various multiplication factors to the seperate Karamba load cases:

    This option allows the corssection optimisation to be done through all the load combinations but is extremely heavy computation wise and does not allow to have a lot of different load combinations

Any thoughts or better ideas?


I do not use the LC factor, except on wooden structures to integrate certain regulatory factors or for a vibration analysis.

I always use the second option, because on large models, the relationships between the vertical load (applied on the roof for example) and the multiple cases of wind (applied on the facades) can completely change the distribution of forces in the model, and therefore the local calculation of each bars.
It is therefore never easy to know which load case is main or not.
For optimisation i prefer on this case use Galapagos, Goat or Octopus.

It takes a long time to do and program. However, the computation time of the Karamba solver is much faster than most civil engineering software that I use (without mentioning them :slight_smile: )
Especially when you have to be flexible and have a parametrical design

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Hi @augustin.ceillier,

i think you are approaching the LC Factors wrong. At this stage there is no possibility to do load combinations. The values that you are inputting into the model view are just simple multiplications of the view output of the model, they do not affect the actual calculation.

At this stage only load cases are available, so if u wish to really make a load combination, you have to set multiple types of loads for each load ‘case’. For example, LC0 gravity, LC1 deadload, LC2 1.35.gravity+1.35.deadload. Karamba will not combine these for you automatically.

The cross section optimisation component automatically optimises for all load cases applied.

hi @matttam

When you say “LC factors do not affect actual calculations”, are you talking only about the cross section optimization component?

Because, do we agree that the LC factors multiply all the output values ​​(displacements, forces, stresses and reactions) in the model for each load case?

If this is true, for a simple structure, (without the use of cross-section components), can you apply the LC factors to be equivalent to certain load combinations?

Hi @augustin.ceillier,
in Karamba3D 1.3.2 the LC-factors provided at th ‘ModelView’-component influence the output of those components which take the load-case to be displayed from the selection of the ‘ModelView’-component. These are e.g. the ‘BeamView’-, ‘ShellView’- and ‘ShellLineResults’-component.
At the moment one has to apply the load-factors when defining the loads and load-cases.

Thanks for the clarifications!