Design of shallow moment resisting foundations 3

[CivilSigma]

I have been reading about the design of shallow moment resistant footings using "Foundation and Anchor Design Guide For Metal Building Systems" by: Alexander Newman
The author discusses the design of the foundation to lateral loads.

Horizontal thrust onto the foundation from a column above is only used to design the foundation wall below to moment and shear (M = force * depth of wall).
However, the author does not design the footing for this moment.

Isn't the moment transferred from the foundation wall to footing below? Should it be considered in the design of the footing?
The footing is only designed for moments from net earth pressures. I find it counter intuitive that we don't design the footing from the moment coming from the wall above.

 

[CivilSigma]

@r13:

Yes, thank you for your corrections.
For both the left and right cantilevers Mf = qx^2/2 for equilibrium.

 

[r13]

Yes, if q is uniformly distributed pressure. I used to design the footing base uses q[sub]max[/sub] as uniform distributed pressure.

 

[HTURKAK]

It matters depending on whether tie rods are provided or not. Moreover, your sketch implies the wall with substantial height (l on your sketch ) is not a simple grade beam with limited height and will experience active soil trust from interior soil and fill.

If tension rods are not provided, the wall and so the footing will experience the loads from gravity (vertical downward and outward horizontal direction ), active thrust from soil and horizontal load from wind / seismic ( horizontal and uplift )...

Another point, the geotechnical design and structural design of the footing differs. You are expected to show that the stresses developing under the footing do not exceed the allowable soil stress and allowable soil stresses for wind and seismic is increased 30% for wind and seismic loading.

I want to remind also, if you provide more details you may get better answers.