Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: footings a beam or a slab?

[Subject Prev][Subject Next][Thread Prev][Thread Next]
In a message dated 98-09-30 18:13:32 EDT, you write:

<< I have a case where I have a footing that is 24 inches wide and 16 inches
 deep.  I found that the footing only requred minimum steel reinforcement.  In
 the longitudinal direction I used 3 #5 bars and in the transverse direction I
 used #4 @ 6".  >>

Marlou -

Is the footing part of a slab on grade system or a raised floor system?  Is
there a stem wall on the footing?  What is your allowable soil pressure?

Typically, we don't provide any transverse steel in the bottom of our
continuous footings other than the hooks from the verticals in the stem wall
if a stem wall exists.  Without a stem wall, typically we have no transverse
steel at all (I assume you're discussing steel across the 24" distance of the
footing).  This is very standard in residential, Type V construction.  Also,
we do provide longitudinal steel in the top of the footing (not so standard).
For a 24" wide footing such as yours, maybe 3 - #4 top and bottom.  Much of
this is justified by low (1000 - 2000 psf) bearing pressures which just can't
develop much load in the footing.  Since the footing is so small (assuming a
bearing width of 8" centered on the footing, the cantilevered part of the
footing is 8" long x 16" deep), the shear force is within a distance "d", the
corbel force is nominal due to the low soil bearing, and the bending is
trivial.

Good luck.

Bruce Resnick, SE
Parker Resnick Str. Eng.