2D model or 3D model for stress under foundation?

[n3jc]

Hi, heres the question - if we want to calculate contact pressures under foundation, which model is more accurate/better 2D or 3D? SEE ATTACHED FILE.

I think plane - 2 d model has too conservative results (stress too big because it doesnt count the contribution/effect of other foundation nearby?)
I like 3D model better. Is it OK? How do you guys calculate this.

tnx for answers.

 

[Okiryu]

If this is for real work, I would just consider plane strain conditions (2D model) since you are analyzing continuous footings.

 

[Mccoy]

n3jc,
sorry if I express my opinion one month after you posted.
What you call the 2D model seems to consider an infinitely rigid strip or a uniform loading.
On the other side, the 3D model has non significant variations in load, practically uniform from the engineering point of view, but a with an absolute value which is intermediate with respect to those of the 2D model. So rigid beams which are interacting in the overall loading distribution?

I would choose the 3D model since the FEM model which appears to have been used is able apparently to consider the interactions among the single foundation members-beams in the grillage structure.

http://www.mccoy.it