Spread footing of steel frame - rotation?

[n3jc]

Hi
Im asking why/if it is necessary to design a footing under a steel column to a moment that is caused by a horizontal reaction Rh?
Wouldnt a steel column (frame) prevent a foundation to rotate (and hence cause extra pressures at the edge of a footing)?

what about passive soil pressure that acts against footing to rotate (turn over)?

tnx for help / explanation.

Regards

 

[Tommy385]

Im asking why/if it is necessary to design a footing under a steel column to a moment that is caused by a horizontal reaction Rh?
Wouldnt a steel column (frame) prevent a foundation to rotate (and hence cause extra pressures at the edge of a footing)?
Isnt it the same thing?

If you go with passive soil pressure you will have a large horizontal deformation, check what happens with your frame internal forces if your foundation moves say 5cm.

 

[civeng80]

I have always tied in the column base with the slab so that the horizontal reaction is resisted by the reinforced slab through tie action. The pads are just designed for vertical downward load and wind wind uplift if any.

 

[Mjkkb2]

it has to be resisted somehow. Either by the footing mass counteracting the OT moment or by utilizing the passive pressure (risky as it requires a decent movement for the pier/footing passive pressure to be utilized) or by other means (like suggested above) using slab reinforcing.
The latter is a very common practice for pre-engineered metal buildings where a hairpin bar is installed to take out the horiz/thrust force from the column base into the slab.