What is the gravitational acceleration used for?


We use Karamba to create a structural model, and then we export it to json, and import that json into our own structural library. We currently only convert the model itself to our library, and no results at all.

In our library we use SI units, and we use 9.81 m/s2 for gravity. We also use density for the materials, instead of specific weight.

Now, in order to correctly convert the Karamba model to our schema, I need to understand how gravity is really used.
I have a simple model right now with beams and a shell. I have made trapezoid and shell const cross sections, and it’s all concrete. I have added a gravity load and a MeshLoad const to the shells.

I then run the analysis with gravity as 10 and as 9.81. The only thing that changes is the mass of the structure, while all other results don’t seem to be affected at all by the value of gravity. So without having to create a comprehensive model that tests all different types of loads and analyses and whatnot, I would like to ask what influence the gravity has on the karamba model and the structural analysis, if any besides calculating the mass.

If it has no influence, then that’s fine, and in the conversion to our own library, we’ll just always use a gravitational acceleration of 10 in order to obtain the correct densities from the specific weights.

Here’s the model I used:
testmodel_karamba.gh (53.8 KB)

Thanks in advance,

Hi Knut,
in Karamba3D the constant of gravity is only used for converting the specific weight of materials to specific mass.
It used to play an additional role in the computation with Imperial Units but this not the case anymore since version
– Clemens