Slab Diaphragm

[RRufino]

Hello,

Please help on the following. I've a concrede model, over this will exist a steel structure. Steel forces were imported to concrete model using reactions to nodal forces macro (tks Rafal).

My issue is on foundations, i want to take advantage of ground floor slab (raft?) to distribute horizontal forces equally to every supported points. Since this slab is over piles i've made several tests to model this behaviour without sucess, supported nodes are 10cm above slab plan.

In attachement i've made a slab model called "Test" that is equally to pre-defined Slab-Flexible diaphragm but without FE...in this case sometimes i get "incorrect panel calculation" and looking to Fx reactions they make no sense. I also predict that with this slab model i will not get the behaviuor i wrote on previous paragraph.

Thanks for any tips,

RRufino

[Rafal.Gaweda]

Using my addin 🙂 or manually correct panel coordinates

[Rafal.Gaweda]

Another my macro and ...

[RRufino]

Thanks Rafal,

I'm trying to replicate what you did...but what are you trying to show me on second table from second image?

In this case how do i get rid of this short calculation elements?

[Rafal.Gaweda]

I'm trying to replicate what you did...but what are you trying to show me on second table from second image?

Short element is causing instabilities; short element is generated by inaccuracies in these coordinates

In this case how do i get rid of this short calculation elements?

Correct Z coordinates for marked nodes.

[RRufino]

I did what you ansewered and i still got instability (type 3) on calculation node 45. (plz see attachement)

When i ignore this warning...seeing Fx reactions to self-weight they do not seem ok...

In your opinion what is happening?

Thanks Rafal

[Rafal.Gaweda]

My file attached

- geometry corrected

- kinematic links off

- DSC off

[RRufino]

Thanks Rafal, no more warnigs.

How about 2nd paragraph: "My issue is on foundations, i want to take advantage of ground floor slab (raft?) to distribute horizontal forces equally to every supported points. Since this slab is over piles i've made several tests to model this behaviour without sucess, supported nodes are 10cm above slab plan."

Should i use Rigid Diaphragm?

[Rafal.Gaweda · Accepted solution]

distribute horizontal forces equally to every supported points. 

Only this way:

- apply reduced force to geometrical center of supports

- apply rigid links (as RLINKs)

[RRufino]

Thank you Rafal.