Spring element

[mari.95]

Hi to everyone, I have some questions... I have to model a steel beam of a tunnel and simulate a fall of a block of the concrete coating, so I have to calculate the displacement at the top of the beam. I think to a 2D model. The conditions that I want to simulate is the fact that around the beam we have the concrete coating and then rock which governs the deformations so I think to springs in compression with a Winkler stiffness (with a normal component and a tangential one). Then I have to simulate the external conditions of the beam as fixed joints due to the dowels with bolts M16 that are modeled also with two springs. So the questions are:
1)How can I model the springs that allow taking into account the interaction between rock and beam, in STKO. Maybe with zero-length elements?
2)And consequently how can I model the springs for the fixed joint?

*I have attached some significant figures:
-Cattura 1: The tunnel pattern;
-Cattura 2: External conditions (dowels);
-Cattura 3: springs that simulate the rock interaction with the steel beam.

Thanks in advance for your availability.
Mari

[STKO Team]

1)How can I model the springs that allow taking into account the interaction between rock and beam, in STKO. Maybe with zero-length elements?

It really depends on what kind of interaction you need to represent. Is it a simple contact? Is it a cohesive interface with degrading tensile and cohesion? Do you need an interaction between normal and tangential components?
Zero length can work, but the normal and tangential component will be un-coupled.
Also with zerolength pay attantion at the local-axes... in your case you can assign a cylindrical one.

2)And consequently how can I model the springs for the fixed joint?

You can simply fix them. Or use a zerolength with an elastic material to simulate its finite stiffness

[mari.95]

It is a simplified model, I don't want to simulate the contact I just need to model the beam and the concrete fall on it for a deformability verification. When the fall of the concrete block occurs on the beam, this would tend to deform towards the extrados in areas adjacent to the loading area, while the ground, pushing on the beam, reduces the amount of this deformation, consequently reducing the displacement at the top. Not considering this contribution, the displacement would be overestimated. For this reason, I think to put some spings in compression with a normal component (only in compression) and a tangential one, so I think that is necessary interaction between the two components. Do you have any suggestions?
Thanks again!

[STKO Team]

I think the easiest way for you is to start modeling it, asking specific questions when you face some issues or doubts. This question is too general to be answered in a forum.
I also do not fully understand what you mean by "fall of concrete block". Do you want to simulate a concrete block falling and impacting the beam in a transient analysis?