redistribution of reduced forces for storey between walls and columns

[GabrieleNovembri1027]

Hi all,
I am doing tests to determine the distribution of horizontal forces between the columns and walls, and I noticed a behavior that I can not understand.
In the simple structure reported in the figure I applied a distributed force on thr panels of the floor in the X direction equal to 10 KN / sqm. The surface of the panels is 144 square meters and the force applied to the plan is so equal to 1440 KN

in the table of reduced forces for storey the value of the force of is equal to 1440 kN. ...OK....

from the table i read:

• -668,07 KN acting on columns
• -771,93 KN acting on walls

The sum is equal to 1440 and the direction of the force due columns and walls is opposite to the acting force . ... OK ...

If I make the seismic analysis in X-direction (modal analysis, seismic analysis with DM 14/01/2008, parameters by default) I get a situation that seems to me strange and wrong but, mainly, I do not understand.
The total mass of the structure is equal to 96387.50, and the force is reduced to the plane -25.32 KN. I suppose FX is the force due to seismic activity. It is oriented towards the negative X direction

The force acting on the storey is divided up as follows;
•     18.79 kN acting on the columns (positive?? In the X direction ??)
•    -44.11 agents on the walls (Negative?? opposite to the X direction )

Why the forces on the columns and walls are ALWAYS in the opposite direction ????.
really do not understand.
Any suggestions?

[jad.dellel]

Hi Gabriele,

Can you add the file , please?

[GabrieleNovembri1027]

Hi Jad,

I send you attached the model. Please note that I found the same thing also on large models (see picture)

Tanks

[GabrieleNovembri1027]

Hi
I realized that something went wrong in the previous post.
I'm sending you a picture of a more complex model made ​​with the 2011 version and the small test model

I noticed that if you simply open the model with the 2012 version results are shown like in the image and seems correct.

If you recalculate the structure The situation changes as shown in the figure.

why the values change ?  Which are the correct values? (I think those of 2011)

I hope you have a some time to devote to the issue that seems to me quite critical

Thanks

[jad.dellel]

Gabriele,

Is-it the right model?

[jad.dellel]

Gabriele,

I think the problem comes from the load to mass conversion:

When I check your file CON SISMA.rtd, I found something wrong on the "Load to Mass Conversion" tab:

Logically, you should have the 3 loads: 1-Peso proprio structture (you disregard density in modal analysis), 2- Permanenti non structturali, 3- Variabili.

[GabrieleNovembri1027]

hi Jad

I don't know if you have seen the post 07-13-2011 12:08.
It is very strange but if I open a model calculated using the 2011 version with the 2012 version the following happens:
a) if you do not recalculate the structure the sign of the walls and columns seems coherent and values ​​seem right;
b) recalculating the structure values ​​are with conflicting signs and don't look right.

Yes, it is true.

The values ​​of the of the loads-mass translation are wrong. I don't know why. I did a model recover for cleaning it from the results because the file was too large. In the following image you can see the same model after recover. There is another Bug ?

In the model attached the loads are right. However the problem does not depend on conversion of loads. The problem always seems the same as shown in the following figure in a model after a load correction.

Thanks

[jad.dellel]

Gabriele,

The method for calculating reduced forces for stories has been changed to sum applied loads for a storey’s node. Previously the calculation integrated internal forces in storey cross-section.

You can also read it on "Whats new?"- Results presentation:

http://docs.autodesk.com/RSA/2012/ENU/filesROBOT/GUID-1A9A65AF-8104-4A8E-AD9F-9A351367DA0-1.htm

[GabrieleNovembri1027]

....and so we are back to the first question:

Why the forces applied to the columns and walls have always opposite direction ?

thanks

[GabrieleNovembri1027]

...I understand that in the end there is no answer to my first question:

Why the forces on the columns and walls are ALWAYS in the opposite direction ????.

Thanks