New user of Robot

[Anonymous]

Hi,

I am new to Robot and trying to learn how to use it and would appreciate if someone could have a look at this file to see if generally its ok?

Its a check on an existing warehouse structure but I am getting errors / messages which I don't understand.

My background is more StaadPro.

1. The only loads included in the file right now are the existing loads as follows:
   1. Self-weight of the structure.
   2. Superimposed dead load on the roof of 1.5kN/m2 which is for the weight of the roof panels (137mm thick kingspan KS 1000, which weight 13.7kg/m2) and the fall arrest system on the roof. This 1.5kN/m2 looks very high to me but I have applied it anyway. But this 1.5kN/m2 could be deemed to include services hung off the rafters.
   3. Variable roof loads of 0.75kN/m2 and a 1.0kN point load (again both from Arups original design).
   4. Wind loads.
2. I am getting quite a few instabilities so I added in some supports, just to get the model going but these will need resolving one way or another. I am still getting one instability at node no. 144 which I can’t yet iron out and don’t understand why I am getting it.
3. I also get a message about missing load cases in the combinations but don’t understand what the issue because they look ok to me.
4. I have yet to add serviceability checks.

If anyone could have a look over I would much appreciate it. And explain how I can get rid of those errors/instabilities.

And just check generally if it is analyzing correctly?

regards,

Patrick

[Artur.Kosakowski]

Hi Patrick,

First of all welcome to the Robot forum 

IMHO the instability is due to excessive releases. I blocked RX in the definition of the pinned-pinned release and it is no longer reported. If you make such change you may want to check MX torsional moment on the bars you applied this release to to see if the values are close to zero and release Rx where needed. You may also use partial RX release instead.

In terms of the correctness of your model - I'm not sure what is the reason for a support in node 144. In addition you may want to check the values of displacements which seems to big (increase of section sizes may be required).

The good resource for determining the cause of the instability and checking the correctness of the results is the recording of the 16th Robot webinar. For steel design I'd suggest the 3rd one. The recordings of the webinars are available from here.

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