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Retaining Wall Footing Question

Retaining Wall Footing Question

Retaining Wall Footing Question

(OP)
When designing the reinforcement for the heel of a cantilevered wall, why is it based on the moment produced by the soil over heel, self weight and surcharge? Why is not just exactly the same moment as in the bottom of the stem? From a practical standpoint, how can it be any larger than that?

Thanks in advance.

RE: Retaining Wall Footing Question

The rebar dowels from the wall stem to the footing carry the moment into the toe of the footing, where the dowel horizontal leg in the footing is on the lower face of the footing.

The transverse rebars at the top face of the footing carry the moment caused by all the weight on the heel of the footing as the heel theoretically lifts up.

RE: Retaining Wall Footing Question

typo-

The rebar dowels from the wall stem to the footing carry the wall moment into the toe of the footing,...

RE: Retaining Wall Footing Question

The moment at the bottom of the stem is distributed to both the heel and the toe (minus the SW contributions of the footing selfweight). The moment will usually be taken at the face of the wall and not at a working point at the center of the wall, so the toe and heel moments will not add up to the full stem moments. So using the full moment for the heel would be a conservative approach.

RE: Retaining Wall Footing Question

(OP)
Except, the moment in the heel is ALWAYS larger than the stem moment using traditional retaining wall analysis (which I don't agree with)
It is based on the self weight of the footing and overburden and assuming you are at the verge of overturning.
In reality, the moment in the heel can never be greater than the stem moment. Look at an FBD right were the stem joins the footing.
The moment in the heel is only there due to the torque of the stem.

RE: Retaining Wall Footing Question

The only way I can see the heel moment being greater than the stem is as Fixed Earth mentioned, if there is a large axial load on top of the wall. What do you call "traditional" retaining wall analysis?

I never chose a retaining wall geometry that puts me on the verge of overturning, my stability ratio is 1.5. Therefor i have contact earth pressure acting on the heel and the components of the heel moment are soil over heel, self weight and surcharge with the contact pressure working in the opposite direction.

RE: Retaining Wall Footing Question

(OP)
Traditional analysis bases the heel moment on the weight of the overburden, footing self and surcharge - which always gives a moment greater than the stem moment.

RE: Retaining Wall Footing Question

(OP)
..that is under normal conditions with the heel sized long enough to prevent sliding and no shear key.

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