Master-Slaves nodes and spring joints

Hello everyone,

I am currently testing Karamba 3D and so facing some problems about how doing my model.

1. I am calculating statically indetermined shells anchored to a concrete structure. To do so, people calculated the displacement of the concrete structure and so gave me the displacements of the nodes and the stiffness of the structure.

My problem is that I don't undestand how to model that stiffness. Do I need to put a zero length spring at the very end of my anchorages?

2. I have shells one above another and, even if they are not connected in my model, they are. In SAP2000 I used master-slaves joints to constraints the displacements of some points to be equal to other points. How could I simulate this behaviour with Karamba?

Thanks a lot for your help and have a nice day!

Replies to This Discussion

Permalink Reply by Karamba3D on May 17, 2016 at 2:01pm

Hello Brice,

regarding your first question: you could try to place a spring between a support and your structure. This is done by defining a beam and then specifying a spring cross section. The latter allows you to set arbitrary translational and rotational stiffness values. For a linear spring you need to take into account the distance between the springs you add.

For solving question two you could also use spring elements and set the DOFs which shall be rigid to a large value (e.g. 1E8). In order to find the right value you need to test the resulting structural response. If the stiffness value is choosen too high the stiffness matrix gets ill conditioned and the results unprecise. In case the value is too low the displacements will not be equal.

Best,

Clemens

Permalink Reply by BRICE CANTENEUR on May 20, 2016 at 1:53am