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Strange calculation of self weight versus quantity schedule

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Message 1 of 6
tony.ridley
414 Views, 5 Replies

Strange calculation of self weight versus quantity schedule

Hi again,

 

Found something strange today........

 

I have a model with overlapping slab panels.  The big slab is 375mm thick, the smaller (overlapping) panel is 160mm thick. 

I saved the model and revise the slab geometry so no panels are overlapping. 

 

When I check quantity schedule, the area and volumes of both models are exactly the same, however the DL reactions are very different.  It seems Robot accounts for the overlapping geometry when adding self weight, but not when calculating areas of slabs.  Strange. 

 

The screen shots below do not show weight of bars etc, so obviously the total reaction will not equal the panel weights.   

 

Quantities, THIS IS THE SAME FOR BOTH MODELS

INCORRECT PANEL QUANTITIES..JPG

 

 

Reactions, OVERLAPPING MODEL

INCORRECT PANEL REACTIONS.JPG

 

Reactions: FIXED MODEL

FIXED PANEL REACTIONS.JPG

 

I can email files if necessary

 

Tony

5 REPLIES 5
Message 2 of 6

Attach the models please.



Artur Kosakowski
Message 3 of 6

coming now via email...

thanks

Message 4 of 6

Hi Tony,

 

Thank you for letting us know about this situation. We are investigating it - for now don't define smaller diaphragms inside the larger ones.



Artur Kosakowski
Message 5 of 6

Thanks,

 

I thought the small panel within the other panels would flag an error anyway ("overlapping panels"), but it did not.  

Does this mean for the 'overlapping panel' error to be triggered, the panel must be overlapping BUT NOT wholly within another panel?  If this is true it seems like a strange logic......

 

Anyway thanks for looking into it,

 

cheers,

Tony

Message 6 of 6

Hi Tony,

 

Such definition is perfectly correct for 'standard' panels (load transfer via surface elements and no rigid links from the center of the slab)  but my personal feeling is that in this case Robot indeed 'allows' for too much. By defining a smaller diaphragm 'inside' a larger diaphragm you not only want to have both of them to be 'united' for transfer of horizontal loads by rigid links but also you want to have trapezoidal and triangular load distribution from the inner panel to elements which are 'outside' it. Assuming that your objective is just automatic self-weight generation on the parts of a floor with different thickness comparing to the 'main' one I would suggest use of a single panel with some surface loads on contours instead till the moment this situation has been fully investigated by the development team.



Artur Kosakowski

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