Containment Slab Design warnings

[Anonymous]

Hello everyone,

I have this containment slab on grade that I have modeled with 8" walls all around it except for one section that has steel framing with cladding (Model attached). I tried to run the calculations on it but seem to be getting the following warnings:

1. No supports
2. Incorrect definition of contour load for the load case 2. Panel no.1
3. Incorrect definition of contour load for the load case 4. Panel no.1
4. The instability (3 type) in the RY direction in the node 3037.

For point 1., I only have a slab that has a KZ value of 15000 kN/m3. That is the only support so I'm assuming that should not cause any errors in my design?

For point 2. and 4., I'm not sure why there is an incorrect definition of contour load? 

Finally point 4. says instability type 3. What is causing this and how should I fix this?

[EduardoMeruvia · Accepted solution]

HI @Anonymous, 

Unfortunately I don't have robot 2019 yet install so can't have a look at your attached model, but from the reported errors I can say the following; 

1. No supports: Even though you have your Kz elastic spring defined for your slab, you still need some lateral restrains UX UY for your structure to be statically determined. This is regardless if the overall forces on your structure should keep it "balance". If it was me i would probably just put a UX & UY node restrain at each corner of your slab and then make sure the sliding forces are design accordingly.
2. Incorrect definition of contour load for the load case 2. Panel no.1: Usually arises when there is a small dis-connection between either your cladding and supporting members or your cladding's plane i.e. it is slightly tilted/twisted at one corner. 
3. Same as 2. 
4. Possibly due to the lack of lateral supports. See if error persist after adding lateral supports on your model. 

Hope this helps. 

[Artur.Kosakowski · Accepted solution]

Hi @Anonymous

The corrected model with KX and KY added in the bottom panel thickness.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[Anonymous]

@EduardoMeruvia: Thank you kindly for the clarification. It gives some insight on how to model structures like this in the future.

@Artur.Kosakowski: Thank you for the updated model and providing a different approach to address the point #1.