Modeling Link connection between frame and infill walls

[M.Sheikhi]

Dear SeismoSoft Support Team,

I am currently working on a research project involving the nonlinear modelling of Autoclaved Aerated Concrete (AAC) infill panels in SeismoStruct and would appreciate your guidance regarding the modelling of frame–infill interaction while considering the construction gap between the infill wall and the surrounding frame.

In the SeismoStruct User Manual (Appendix F, p. 503), it is stated that:

"Users may wish to introduce link elements between the frame and infill panel nodes, in order to take into account the fact that the infills are commonly not rigidly connected to the surrounding frames."

Furthermore, in the SeismoSoft Forum, your team mentioned that gap/link elements can be used in refined models to represent this behaviour (viewtopic.php?p=11440#p11440)

Could you please provide a simple example model or sample file showing how to model the interaction between a frame and infill panel using link/gap elements while accounting for the gap between them?

Thank you for your support.

[seismosoft]

Unfortunately, we do not have any models available that we can provide. The link elements are used to model the interaction of the infill panel to the surrounding concrete members, connecting the nodes of the two.
Seismosoft Support

[M.Sheikhi]

Thank you for your response.

1.Just to clarify further, when you mention that link elements are used to connect the infill panel to the surrounding concrete members, is this limitation specifically intended for reinforced concrete frames only? How should the same modelling strategy be extended to steel frames?

2.In particular, when link elements (e.g., gap) are used to connect frame nodes to infill panel nodes in order to account for the construction gap and the delayed engagement of the infill (i.e., activation after contact), does the formulation internally lead to a combined spring system once contact occurs?

3.Additionally, considering that infill modelling in SeismoStruct is typically based on strut formulations with virtual nodes, could the introduction of such link elements lead to any numerical instability or over-constraint issues due to the interaction between the link formulation and the infill element?

I would greatly appreciate any clarification on these points.

[seismosoft]

Hello,

1. There are no general rules for every building. You should make the modelling decisions based on your building configuration. The typical modelling in most practical applications is without link elements to model the gaps or the flexibility of the contact surface.
2. Not sure what you mean. The two elements (link and infill) operate in series, but independently. Note that the offsets in the infill are rigid.
3. SeismoStruct is very stable numerically. I would guess that there will be no divergence problems with over-constraint issues but you will need to check things yourself.
Seismosoft Support