Link Element without tension capacity

[MSWC]

Hello everyone,

I am currently modelling an inelastic infill panel with link elements.
The link elements (trilinear asymmetric) should have no stiffness in tension. Is there a possibiltiy to activate the link element just for compression? However when I assign very low stiffness the calculation only finishes if I allow very high tolerances in the convergence criterias, which seems to be very inaccurate.

Is there a way to model a trilinear link element just for compression or is a certain amount in tensile direction needed for this link element? Which values would that be?


Thanks and have a nice day!

[seismosoft]

Using the trilinear asymmetric curve, you should be able to model a curve without resistance in tension.
As it seems, this causes convergence difficutlies in your model, however this is not because of the link element itself.
Do you get convergence, if you remove the infill panel?

Seismosoft Support

[MSWC]

Thank you for your answer!

I get convergence if I remove the panel. My input values for the infill seem to be reasonable, however it does not converge with the default values for the infill panel as well. Also the model converges very well with my values for the infill and without the link elements.

[MSWC]

Additional Information:

A gap/hook element with no tension stiffness converges also!

[seismosoft]

Can the problem be in the compressive part of the curve, rather than the tensile part?
How do you connect the link element at the centre of the infill with the RC members. Is the structure able to support the gravity loads of the members around the link element?

Seismosoft Support

[MSWC]

Thank you for the answer!

A trilinear symmetric curve with the values I have assigned to compression works fine.

A bilinear curve works fine with a very low value assigned to the tension stiffness.

It also diverges for the default infill + default trilinear link.

I connected the link elements to the corner nodes of my frame and created a coincident node. Between these two nodes I assigned the link element and the coincident node is connected to the masonry panel. The link elements are aligned horizontal with F1, left nodes pointing in x-direction, the right nodes pointing in negative x-direction. The F3 direction is aligned upwards for bottom nodes and downwards for the top nodes.

How do I make sure the structure can bear the gravity loads? It works fine without the link elements.

[seismosoft]

Since you use the infill panel element to model the infill, what do you need the link elements for?
Seismosoft Support

[MSWC]

I want to simulate the influence of the mortar(should have trilinear behaviour) between frame and infill and take into account that there is just low to zero tension force acting between the two parts. Since the user manual says link elements between frame and infill are generally possible, this seemed to be a good way.

[seismosoft]

Link elements may be used to simulate the entire infill behaviour, and they are employed together with elastic frame elements. Using a link+infill element combination does not seem to be a good modelling tactic.
Please refer to the details of the infill panel element (user manual and corresponding references). It consists of 4 diagonal struts and 2 shear struts, that provide different modelling capabilities and can adequately model the influence of the mortar.

Regards,
Seismosoft Support

[MSWC]

The modelling tactic link+infill is explicitly proposed in the user manual to take into account the non rigid connection of frame and infill. Therefore it seemed this idea was generally possible.