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## Robot Structural Analysis

Mentor
Posts: 198
Registered: ‎10-08-2011

# Total self weight Reaction Pb

435 Views, 7 Replies
11-20-2012 03:37 PM

I ve modeled a building by using concrete one directionnal panels ( named 16+4 , 20+5 and 25+5 on the panel table ).

these panels are entered with an equivalent self weight as they where a plain concrete panels.

In the firt method , the model calculation of these panels is :

1. Finite element type : shell

2.stiffening diaphragm : flexible

3.Transfer of loads : one way. (simplified )

In the second method , the model calculation of these panels is :

1. Finite element type : shell

2.stiffening diaphragm : flexible

3.Transfer of loads : Analytical ( finite element ).

when analysing the reaction table , ive found that there is a big difference between of total selfweight of the building

(model 2 = 2624.75 t ; model 1 = 2343.37 t).

Please indicate how can i send you these two models for verification.

Urgent please

thanks

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Product Support
Posts: 4,544
Registered: ‎12-17-2010

# Re: Total self weight Reaction Pb

11-20-2012 11:53 PM in reply to: faisal.aaouatif

Please check first if the total sum of loads is equal to the total sum of reactions. You can see these values in the reaction table. This is to check if all loads are correctly applied. If yes, then I suggest that you leave only the top floor deleting all others and apply fixed supports at its bottom for both models. Then calculate both models and compare results. Do the same for each of the floor till the moment you find the one that causes difference. Then you can investigate much smaller model which makes fiding the exact cause of the difference much simpler.

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.

Artur Kosakowski
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Mentor
Posts: 198
Registered: ‎10-08-2011

# Re: Total self weight Reaction Pb

11-21-2012 02:41 AM in reply to: Artur.Kosakowski

Ive checked Ground and 1st floor and i think the problem will be the same for other floors :

For the 1st floor for ex (see model attached) :

1 Calculation 1 : Panels (16+4 and 20+5 ) are not meshed and tansfer of loads is one way ( simplified ).

2.Calculation 2 : Panels (16+4 and 20+5 ) are meshed and tansfer of loads is one way ( simplified ).

3.Calculation 3 : Panels (16+4 and 20+5 ) are meshed and tansfer of loads is analytical ( FE ).

I have found almost the same results ( total reactions ) between calc 1 & 2 , but results are very different with calc 3.

Dont understand why ...

Please , find attached the model (saved without results) , and results analysis.

thank you

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Product Support
Posts: 4,544
Registered: ‎12-17-2010

# Re: Total self weight Reaction Pb

11-21-2012 05:09 AM in reply to: faisal.aaouatif

Is there any particular reason why for half of the slab you decided on FE distribution and used the triangular and trapezoidal one for the rest of it?

Artur Kosakowski
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Mentor
Posts: 198
Registered: ‎10-08-2011

# Re: Total self weight Reaction Pb

11-21-2012 07:06 AM in reply to: Artur.Kosakowski

Yes :

All slabs 16+4 , 20+5 and 25+5 are precast and transfer loads only on one direction , other slabs are plain concrete one are FE distributed.

Thanks

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Product Support
Posts: 4,544
Registered: ‎12-17-2010

# Re: Total self weight Reaction Pb

11-21-2012 07:52 AM in reply to: faisal.aaouatif

The problem is with the triangular and trapezoidal load distributions for panels that have common edges with panels with FE load distribution. This is what we will be investigating and for now I would propose two solutions to decide on:

1. Use the bi-directional distribution method instead of FE one. In other words replace:

with

or model precast panels with the orthotropic thickness

and use FE load distribution for all panels.

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.

Artur Kosakowski
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Mentor
Posts: 198
Registered: ‎10-08-2011

# Re: Total self weight Reaction Pb

11-23-2012 12:14 AM in reply to: Artur.Kosakowski

Thank you Artur ,

Im going to investigate the second method, but i have already modified the hole model by connection only needed slabs edges with support does need transfer of loads.

Thank you VM

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Mentor
Posts: 198
Registered: ‎10-08-2011

# Re: Total self weight Reaction Pb

03-20-2013 09:28 AM in reply to: Artur.Kosakowski

Problem resolved ?

Thank you

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