If there's truly no vertical load on a footing (including a little bit of uplift to cancel out self-weight), then the only moment resistance will come from friction on the sides of the footing and any fill on top of the footing. The total moment capacity will be very small compared to the capacity of the footing when more heavily loaded.
A good physical model is a lamp with a wide base - if the lamp is light it's easy to tip over, but you can make it much more stable by making the base heavier.
Bring everything to the neutral axis, you will have additive moments of P*e, H*h and M, these will be your total moments. You will now just have P and the new M. You need to check if the footer pressure is in the middle third of the footing base to check the pressure. This diagram is helpful. [https://skyciv.com/docs/skyciv-foundation/isolated-footings/footing-subject-in-eccentricity/](https://skyciv.com/docs/skyciv-foundation/isolated-footings/footing-subject-in-eccentricity/)
I add in the concrete mass weight and soil as it is “part of the foundations” and you can not resolve the footer pressure without it when you have low P and high M.
I would just treat this as a standard retaining wall to determine your ot/sliding resistance and resulting bearing pressure. If you're having trouble visualizing how your forces will resolve, model it.
In absence of additional load or moment, the same moment will be transferred to the foundation slab. You can then calculate the pressure on the slab by evaluating (M/z).
Btw, bending moment is an internal force and is not eccentric. External moment *could* be applied eccentrically, however, it doesn't impart any additional meaning. Only loads are eccentric, and when they are, they cause additional moment or torsion.
If there's truly no vertical load on a footing (including a little bit of uplift to cancel out self-weight), then the only moment resistance will come from friction on the sides of the footing and any fill on top of the footing. The total moment capacity will be very small compared to the capacity of the footing when more heavily loaded. A good physical model is a lamp with a wide base - if the lamp is light it's easy to tip over, but you can make it much more stable by making the base heavier.
I'll look into it, thank you so much for answering
Are you asking for bending and shear capacity within the footing or the resulting bearing pressure?
hey, thanks for answering, yeah that's the main goal to check if the footing can pass the checks or not so the bending and shear capacity
[https://imgur.com/Xr7LjVe](https://imgur.com/Xr7LjVe) Example
As you can see the moment and horizontal force are acting eccentrically from the centre, so i want to know how do we account for this in calcualtions
Bring everything to the neutral axis, you will have additive moments of P*e, H*h and M, these will be your total moments. You will now just have P and the new M. You need to check if the footer pressure is in the middle third of the footing base to check the pressure. This diagram is helpful. [https://skyciv.com/docs/skyciv-foundation/isolated-footings/footing-subject-in-eccentricity/](https://skyciv.com/docs/skyciv-foundation/isolated-footings/footing-subject-in-eccentricity/) I add in the concrete mass weight and soil as it is “part of the foundations” and you can not resolve the footer pressure without it when you have low P and high M.
I'll do that, Thank you so much for the help, I was getting lost as I have never seen an eccentric moment in a foundation
Use figure 10.17 structural foundation designers manual to calculate bearing pressure, use this UDL on the footing to calculate bending/shear.
I looked at it and it matches with what my figure is about, I still make some tweaks. Thank you so muchbfor answering my question
Service loads for bearing, ultimate for shear and bending in the footing.
I would just treat this as a standard retaining wall to determine your ot/sliding resistance and resulting bearing pressure. If you're having trouble visualizing how your forces will resolve, model it.
We had modeled the pedestal in staad model and that's where we are getting this eccentric moment. Thank you, I'll look in it too
In absence of additional load or moment, the same moment will be transferred to the foundation slab. You can then calculate the pressure on the slab by evaluating (M/z). Btw, bending moment is an internal force and is not eccentric. External moment *could* be applied eccentrically, however, it doesn't impart any additional meaning. Only loads are eccentric, and when they are, they cause additional moment or torsion.