karamba

I would like to ask about karamba analysis. In my system there are timber units on top of each other with a angle between them to create a curvature and top of the timber there is a membrane works in tension and hold the wood units together. In between timber units there is no joints or connections so the system acts as one with the membrane. When I work on karamba assemble karamba take timber units as they are connected to each other eventhough there is no membrane. Im adding a picture to make it clearer. My questionis how to set up a karamba analysis where timber units and membrane works together where timber units connected only by the fabric?

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Permalink Reply by Hannes Löschke on December 13, 2014 at 7:31am

My first guess is that you cannot really model this in KARAMBA.

Here's why: Your fabric membrane will have no bending resistance but be able to bear tension loads. In your geometric configuration, the outer chord will get the maximum tension, so this would be okay.

In fact, if you ignore the fabric that is glued to the back of the timber block, all you have is hinge on one side of the blocks. You can model your wooden blocks as solids either by cross bracing beams or using KARAMBA shells.

By default, beams are connected as if welded. You can modify that with the KARAMBA hinge component. If modelled with beams, the outer beam chord will get all the tension, while the inner chord will get all the compression. That if okay for the fabric hinge, but the compression forces in reality do not concentrate at the inner tip of the block, but distribute along the connection plane.

If you insert connections between the inner and outer chord, the compression forces will start to distribute, problem is that also the tension will distribute. There is currently no way I am aware of, to define a connection that will take compression but not tension.

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