that is to say slabs supported by columns.
which must be avoided by all means.
obtain equivalent spans for this type of slabs.
by a black cardboard sheet which is supported on four columns.
in the parallel direction here, and also in the direction parallel to these two sides.
a deformation which is larger in the middle than on the edges.
to make a little experiment similar to this one.
and then I am going to represent the part of the trusses which is only in compression.
which go towards the column.
to go down towards the column.
diagonals in compression which are supported by this column.
is obviously in compression in this zone here.
and this can lead to the phenomenon which we call punching.
at least the horizontal bars does not have much effect.
And potentially, it can lead to the falling of the slab.
and that this collapse spreads across the whole building.
of how to fight against punching.
For the moment, I would only like you to know that it exists.
How can we tackle punching?
in his first flat slabs constructions.
and that Robert Maillart called a mushroom.
but in a more gradual way through this big mushroom.
and that really looks like mushrooms in this configuration.
without any width changings, an entirely flat slab.
to give us the equivalent spans.
we can reach a value of 0.82.
sometimes a bit smaller though.
which could even go down to about 0.6.
which can lead to the punching phenomenon which must be avoided by all means.
but we will have to take it into account during the dimensioning stage.
their values range between 0.9 and one in most cases.