Load Take Down Mismatch

[Anonymous]

Hello,

I have a conctete building with core walls shown above, when I did the load take down by hand, the reaction force by each column is much higher than what I get from Robot model.

Also, it seems that the total reaction forces at the bottom of all the columns and walls don't add up to the loads that I am putting on the strucure. Any idea?

I already tried to reduce the slab moment of inertia to 0.01 but this doesn't seem to be a reasonable solution.

Thank you,

[mustafahesenow · Accepted solution]

1

[Anonymous]

Thank you for the response.

One more question for this: This is a 17 story concrete builidng and another check I did is to manually sum up all the loads including dead and live applied to the building with selfweight, and I compared the total load I get to the total reaction force from the column supports and wall supports, but the issue is I still got a mismatch and the difference for ULS is about 13% (Model support reaction is lower). Everything in my model is vertical load, there is no wind load applied.

Any idea why this happnes in robot?

Thank you,

[Anonymous]

And I think is the core wall that's doing the weired thing, cause after I took out all the shear walls, the load I calculated by adding up all the applied loads matches with all the reactions from column bottom. Any idea why the shear wall is having such a huge effect on load take down? Or is there any criteria I set wrong for the wall? The wall is modelled as shell and there is no linear release between the wall and the slab.

Thank you,

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@Anonymous wrote:

Hi,

Yes its correct because its finite element method which is related to stiffness the and load path wont be distributed same the manual calculation. how ever if you want to force RSA do it by this way (under Gravity load only ) all what you need is to select all the slabs (floors only not walls ) and choose Slab Rigid diaphragm.

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[mustafahesenow · Accepted solution]

1