Reduction of forces above columns

[nilsarne]

Hi all!

I have modeled a section of a slab with the main part of the slab like 150mm thickness and 3 parts of the slab like 300mm thickness to support point loads. I am using emitters to reduce forces above columns. Why are the moments and the amount of reinforcement reduced with as much as 50 % in the X- and Y- directions?

Is this a reliable result? 

My question is if my model is correctly modeled and the results I obtain from it I can use for the project? 

I will upload the model.

[Krzysztof_Wasik · Accepted solution]

Hi @nilsarne 

Algorithm used for force reduction  is described in Robot help Reduction of forces near supports.

To obtain reasonable results I would suggest mesh refinement at column node. I would recommend mesh size not less than 1/3 of column section size. (10 cm mesh for 30x30 column).

You can find more information in this article as well

[nilsarne]

Thank you for a quick response! Other than the reduced results, the model looks right? I have modeled a slab 300 inside a slab 150 and expect the results to be for a 300mm slab under the point loads. There wont be a panel inside a panel, right? Also, inside the "slab - requirde reinforcement", why does the delfection of the slab not look right? There is no deflection for the 300 mm slabs.

[Krzysztof_Wasik · Accepted solution]

Hi @nilsarne 

Model definition regarding thickness is correct (but for that model I would recommend separate panel definition than define one panel inside another).

Regarding deflection verification for reinforced slab,

Use deflection verification with Stiffness update (FEM) after reinforcement calculation. Displacement discontinuity when Equivalent stiffness method is used was discussed in other forum threads. See for instance

Inconsistent slab deflection

for more information refer to Robot Help.

RC slab calculation