topic model analysis - few error and warnings in Robot Structural Analysis Forum

model analysis - few error and warnings

Cestakar — Tue, 02 Mar 2021 10:56:26 GMT

Hello!

During model analyse I get few warning and errors, like ''no supports'', ''number of missing eigenvalues found=7'', ''execution problem 902'', the instability (3 type)...''. And analysing take it a lot of time.

I have model of house with RC and timber structural elements. Foundation is RC slab raft, I use parameter of foundation elasticity.

I use seismic analyse about Eurocode 8.

Can anyone please look at he model and give me an advice how to fix it?

How I can find / see node with warning message of instability? When I click on it's warning message the node is not showed off.

Thank you very much for advising.

Re: model analysis - few error and warnings

Krzysztof_Wasik — Tue, 02 Mar 2021 17:25:17 GMT

Hi @Cestakar

As far as I see roof element displacement for static cases is too big. it suggests incorrect member connections. When we have static displacement too big dynamic results will not be correct (probably this is the reason for missing vibration modes). Verify roof geometry and correct element connections (maybe additional beams will be necessary). Claddings defined as roof surfaces does not provide any stiffness (especially in horizontal direction).

Re: model analysis - few error and warnings

Cestakar — Wed, 03 Mar 2021 12:43:10 GMT

Thank you. I think tha I solved the problem. With rigid links and blocked directions (Ux, Uy, Uz, Ry and Rz for linear beam in Y direction). Now is calculated analysis normaly and very fast.

I think that warning ''the load has not been distributed correctly'' can I ignore?

How I can find / see node with warning message of instability? When I click on it's warning message the node is not showed off.

Re: model analysis - few error and warnings

Krzysztof_Wasik — Wed, 03 Mar 2021 13:38:45 GMT

Hi @Cestakar

Load has not been distributed correctly regards projected loads in FZ direction defined on vertical walls. Vertical wall has no horizontal area on which load could be projected. In that case sum of applied loads is 0 (this is reason for warning). It is correct for roof panels but not for vertical walls (load should be not projected if you want to load walls vertically).

I do not have your current model but (using your yesterday model) I get instability in node 2195 when static cases are calculated. Since instability occurs in physical node (not in calculation node generated automatically on elements intersections not in element ends) node is selected when instability warning is clicked in messages window.

You can always type in its number in selection filter as well.

Re: model analysis - few error and warnings

Cestakar — Thu, 04 Mar 2021 07:06:39 GMT

Can you tell me where is difference between projected and not projected load?

I'm using this function for example: loads on claddings like wind on imaginary wall plane.

Re: model analysis - few error and warnings

Krzysztof_Wasik — Thu, 04 Mar 2021 09:58:30 GMT

Hi @Cestakar

For wind load I would suggest using PZ in local system (pressure is always perpendicular to surface).

Projected load is usually applied for snow loads where we know code based pressure for flat (horizontal) surface.

See attached picture

See results for projected and not projected loads (1 kN/m) for two beams (10 meters length horizontal and 10 meters length inclined with 60 degrees - cos (alpha) =0.5)