Instability type 3 load equilibrium

[Anonymous]

Hi there,

I am currently checking my model and I came across an instability type 3. I have asked regarding this issue in the past and I was told that this is due to stiffness differences.

At the moment I am checking my model forces and I am finding out that for example in LC 37 the sum of reactions is not equal to the sum of forces. Could you please explain why this is happening? Could this be due to the rigid diaphragm that is assumed for the slabs? Also the sum of reactions should be equal to the sum of reactions of LC 38 which is not happening. The model can be found here https://drive.google.com/open?id=1Xum6Rrz5MzDQDuuLnoIVHpoYTw5P-ETW

Thanks in advance.

[piperr · Accepted solution]

Hi, I had a quick look and is not something you can do in 5 minutes.

First check the deflection and see that there is something wrong in the model.

Delete the releases and add one by one - it takes a while.

See also that there are 4 separate structures- the portals are not tied to the main structure etc.

Short story, your model is not the best you can have, best way is to correct it first and not rely on your Revit export.

Lucian

[Anonymous]

Thanks for your reply. I actually changed the solver as I read in another post and I identified a mechanism. I also redefined all releases.