One way slab - Load distribution not working

[Anonymous]

Hi guys,

I am modelling an existing building with steel framing and one way deck slabs over it.

I have the framing in but when I draw the slabs as a rectangle and put the loads on them nothing gets into the beams and very little into the columns (assume some part goes straight from slab to columns), Bending moments on slab showns that it is not recognizing the beams as it spans from column to column. I have deleted the slabs and re draw again and this made some of them to work (i disply load distribution in colors and shows it also moments on beams make sense). 

I have double checked that beams and slabs are exactly at the same Z position, I have checked for overlaps with adjacent slabs... I honestly don't know what else to do. Beams are as 'Analyze' for the trapezoidal and triangular method.

Attached are a couple of pics. One shows the whole model where the only load distribution working is the roof (modelled as a cladding). The other shows a 'save as' I did, I deleted a few floors, and got 2 slabs to work but at the 3rd one I got stuck again... Oh, last pic showing slab properties used. I have used this in other models and had no problems...

Any help will be much apreciated.

Model is too large to upload can do Dropbox if required.

Cheers.

[Anonymous]

I just realised now that if I stop the one way slabs befor they meet the 2 way meshed slab (last bay close to the core) the beams get the loads correctly but as soon as I extend it none of the beams take any load (it still shows the different colors but no load is generated over beams). Please see picture showing 1 level with each case.

Any ideas on what is causing this? I need to issue a report before friday...

Thanks

[Artur.Kosakowski]

You may try to run the detailed correction to structural axes. If this doesn't help attach the file please. 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Thanks Artur,

Could Yu please tell me how can I do this? Cheers

[Artur.Kosakowski]

See post 8 from:

http://forums.autodesk.com/t5/robot-structural-analysis/some-nodes-are-not-being-included-in-the-sti...

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Hi Artur,

I have tried it and did not work. However I found a temporary way around using claddings as slabs with asurface load as self weight and steel bracing to provide diaphragm action.

Please find Dropbox link attached as I am interested in knowing what is wrong and avoid it in the future. Also I might need to keep working on it after tomorrow's issue.

https://www.dropbox.com/s/reow837h976xg2n/FULL%20MODEL%20-%202.0%20-%20With%20footings%20and%20extra...

Thanks

Ramon

[Artur.Kosakowski · Accepted solution]

Try to set the shell calulation model to the bi-directional concrete slabs.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Thanks Artur,

I see it works but I still don't understand why it didn't work with the previous panel property...it is basically the same as the one you used. Only difference is the diaphragm property (semi rigid in the one I was using and no diaphragm in the one you propose).

Any explanation for this? Thanks.

Cheers

Ramon

[Artur.Kosakowski]

Why this happened requires further investigation. On the other hand IMHO there is no need to "increase" in-plane stiffness of a meshed concrete slab panel with rigid links.