Hi, I am currently working on a small pedestrian bamboo bridge. It will be built as a temporary installation in August and I am trying to simulate its behavior in Karamba. (The concept is to achieve a specific deformation by using a non-standard grid)
Building a flat multilayered grid
Deform the grid by straightening the cables
Tighten the bamboo lashes to maintain the deformation
Is it possible to simulate the behavior of the lashing in Karamba? I have used cylinders to connect the layers (with Clemens’ and Dragos Naicu’s help in a prior post).
Does it generally make sense to simulate a bamboo gridshell structure this way?
And can I use the deformed grid/axes and beam properties for a second or third analysis iteration?
I’m sorry if I asked some unclear questions or something else, I am studying architecture and I’m not very familiar with structural engineering.
Hi @ale_garr,
I would recommend keeping the model as simple as possible.
The transverse elements help distribute localized loads (e.g., a single person) across all longitudinal elements. To investigate this load distribution effect, it should be sufficient to model rigid connections and reduce the torsional stiffness of the longitudinal beams.
I’m do not understand why the longitudinal beams are not spaced equally, especially since the governing load case involves a uniformly loaded bridge deck.
To calculate the initial deformation process, a geometric non-linear analysis is required. This can be done using Kangaroo. While Karamba3D does offer a geometric analysis option, please note that it’s still a work in progress.
I noticed in your definition that you’re using nodal forces to generate the initial deformation. I would suggest using prescribed displacements instead, as this gives you more precise control over the deformation process.
Once you have the deformed geometry, you can evaluate material utilization by applying precurvature loads to account for the initial bending. There’s an example included with Karamba3D that demonstrates this: ...\Karamba\Examples\TestExamples\02_Load\InitialCurvatureLoad
You can access it via the Karamba3D Grasshopper menu under Help → Examples → Local Examples.
Thanks @cp1 for the response. I will try to simulate the deflection using Kangaroo and calculate the utilization afterwards in Karamba.
Do you know if using the Beam component from Kangaroo is best for analyzing the grids behavior?
And can I use the plastic anchor component to resemble the constraint from the 2nd picture from above? (It should work similarly to a slotted hole)
In general, the grid will not be optimized structurally but the aim is to generate a grid that can be deformed in order to match a specific target geometry. It’s more of a design aided workflow.
Adding to the simplicity argument here…I would use the Rod goal in Kangaroo.
You are not really interested in biaxial differential bending properties.
I don’t fully understand the constraint shown. A plastic anchor would entail fixity up to a limit and then a different type of movement.
I would start with a fixed anchor to begin with. Or, if sliding is important, you could use OnCurve which attempts to keep a point on a predefined curve (i.e. is able to slide along that curve).
