Simply supported slab on four sides - linear releases pinned

[skellyRSA2023]

Hi,

I was wondering if someone can help me, I have modelled a simple reinforced concrete slab supported on four walls each side of slab. To assume the slab to be pinned only on all four sides i.e. simply supported I have defined a linear release as ffff at each support side on the slab panel, when I run calculations to obtain moments I get a stability type 2 error? the pdf attached (sheet 3) gives advice on avoiding this I think which is taken from the RSA help? however it doesn't seem to work correctly, as I am still getting hogging moments at supports? is there an example somewhere of this being done? I am basically just trying to obtain the moments and shears of a pinned slab at all four supports i.e. max moments would be in the centre of the slab in each direction. Any hep or input on the matter would be much appreciated. @Artur.Kosakowski 

Thanks,

Simon. 

[Rafacascudo · Accepted solution]

You can not release it all or it will behave like free edges. This is what is causing the instability type 2 which cannot be ignored . And of course ,all results are wrong

You have to ,at least, NOT release UZ  and Uy on at least 2 perpendicular edges. to have stability.

Releasing UZ ,you don´t transfer vertical loads from the slab to the walls

[skellyRSA2023]

Rafael,

Thanks for looking at this, I am slightly confused thou on this thus I have attached the pdf with four sheets, just to ensure I have interpreted your comments correctly, however I think have, as I am get no moments at the supports, however I do get some moments at the corners? see attached. this is generally the way you would look at a precast capping slab etc. 

Simon. 

[Rafacascudo · Accepted solution]

that moment at the corners is normal if edges are not free to translate also in the global Z + direction.

If you set unidirectional release in the Uz+ direction the results will show a little different result