I have modelled masonry sections with shells, and I would like to constrain the shell nodes closest to each beam node so that the shells are rigidly connected to the beams. This feature can be performed by ‘Rigid Link’ in Midas GEN and ‘EqualDOF’ in OpenSees, and I was hoping that a component exists in Karamba3D which can be used in the same way. If anyone is able to point me to this component, if it exists, I would appreciate it.
Hi, if you model a beam connected to a shell then it is automatically rigidly connected at the nodes. You can refer to this example Shells and Beams - Karamba3D
Thank you for your reply. I have referred to this tutorial before, and my issue is that I need to connect a beams to shell layers above and below. This tutorial only covers how downstand beams are modelled with a slab, and when the lines representing these beams are positioned at the surface representing the slab.
However, in the case of a wall represented by two shells which ‘sandwich’ a beam, the beam-line cannot be positioned at both the surface of the upper shell and the lower shell. I have defined the line at the midheight of the gap between the shells, meaning beam and shell nodes do not share the same position in space, as shown below.
I have tried using vertical micro beam elements, or dowels as I have seen some refer to them as on this forum, which exist at each node along a beam and span the height of the gap, to ‘link’ the nodes of the horizontal beam and the shells. However, this only works in so far as these micro-beams end up taking on the load intended for the horizontal beam.
In the script attached, I have experimented with ‘Joint Agent’ component in an attempt to constrain the shell nodes closest to each beam node so that the shells are rigidly connected to the beams. I have defined the beam ID and input the position of nodes which I would like the beam to be connected to in the ‘To’ Geom’ input. So far this has been unsuccessful and I am receiving the ‘Rigid body modes in the system’ error message.
Please let me know if this feature can be performed with the ‘Joint Agent’ component.
In your definition I did not understand in which way you want to utilize the Joints. Maybe it comes from the fact that in Sap2000 and Etabs the term “Joint” is used for connections between the elements. In Karamba3D the term “Joint” is used for an object that controls which forces can be transmitted from an element to the node at its end-point.
The inclusion-point option did not work because some points to be included were too far apart form the surfacee to be meshed. I fixed it here:
As far as modelling assumptions, it’s quite common to actually bridge that gap by making the two surfaces extend up to the beam line. Then you assemble what’s called a connected centreline model where the centreline beam and centreline surfaces of the walls are connected for modelling purposes. There are minor stiffness and eccentricity issues that might appear in certain situations, but as a first approach I would do what the example says, and directly extend surfaces to the beam line, ignoring the actual beam thickness. I hope this is helps.
Thank you for your reply. I have attempted to use short beams/dowels to model the connections as per Clemens’ suggestion. The connected centreline approach could be a useful alternative if I run into problems. Do you know where I could find further information about this approach?
Thank you for your reply and the modifications made to my previous script. I have now attempted to apply the short beam/dowels connections to a larger model with multiple horizontal beams at different levels though I am not sure whether the dowel stiffness and diameter I have chosen is appropriate. Would it be possible for you to review my script?
Thank you for your reply and I understand that you aren’t able to review the script. In any case, would you be able to provide any general guidance to choosing an appropriate diameter and elastic modulus for the short beam elements?
I think the best option would be to use spring-elements for connecting the nodes (see here) then you can freely chose the stiffness-parameters. You will have experiment with different values - if the spring stiffness of the connection is too high compared to the stiffness of the other elements, the global stiffness matrix gets ill-conditioned which reduces the accuracy of the solution.
