Instability RX on node 5

[g.fiscinaW82FY]

Dear Member,

in this easy structure with slabs  one way direction, I have an instability Rx to node 5.

Can someone help me to fix the problem? 

[Stephane.kapetanovic]

hi @g.fiscinaW82FY 

could you share your model ? zip it first.

Best Regards

[g.fiscinaW82FY]

Hi Stephane, thanks for your reply.

In this model I blocked RX at node 5 and the error disappeared.

But why if I don't block  the rotation Rx  to the  node 5 appear this instability, when node 5 is pinned??

Thanks

[Simau]

Hi @g.fiscinaW82FY 

The claddings don't provide torsional rigidity to the beams they connect.
If you replace these claddings with shells you may release supports 1 to 5 in RX, without instability

[g.fiscinaW82FY]

Thanks,

those are concrete slabs. also the slabs (floor) have no torsional rigidity?

why only one node has the instability?

Thanks

Gennaro

[Simau]

@g.fiscinaW82FY 

Also the slabs (floor) have no torsional rigidity?

What i said is that slab provides torsional rigidity to the beams, so you don't need to fix the rx componant for the indicated support.
With cladding, Robot point you only one support with insatbility. That's mean that you have to correct only one support ( You may let the others as they are or correct them too).

[g.fiscinaW82FY]

Thanks.

another question,

there is difference between the element 'floor" and the element "cladding" in the menu geometry? 

Best Regards

[g.fiscinaW82FY]

Hi thanks,

there is behavioural structural difference for a concrete slab if is modeled as a "cladding" or a as "floor" (menu Geometry)

Thanks

Gennaro 

[Simau · Accepted solution]

there is behavioural structural difference for a concrete slab if is modeled as a "cladding" or a as "floor" (menu Geometry)

A cladding has no thickness and its role is only to transfer the loads according to the method you choose (one way or two way).
A floor is a panel with thickness and mechanical characteristics (Young's modulus, resistance, etc.).