Let's consider the following situation: There are 3 identical cylinders each with a weight of 20 tons.
The 3rd one is put over the other 2 like in the picture (but the bottom 2 do touch each other). The 2 bottom ones are on the floor, on Earth in normal environmental conditions.
Ignoring any friction, what force is necessary on the sides of the 2 bottom cylinders to prevent the 3rd one from pushing them outwards and falling between them ?
I have a vague idea on how to calculate this but I really don't remember if there are other things to be considered.