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# Re: One way slab design with point load.

• To: seaoc(--nospam--at)seaoc.org
• Subject: Re: One way slab design with point load.
• Date: Sun, 28 Sep 1997 18:17:36 -0700

```
Joe McCormick wrote:

> At 11:53 PM 9/26/97 -0400, you wrote:
> >
> >What is an appropriate  effective width for a one-way slab with point load
> >occuring at the center span?  I have a 22 foot long span, 12" deep, 4000 psi
> >concrete.
>
> I have a photocopy out of an old concrete design book a senior engineer gave
> me years ago that has the following simplistic assumption for approximating
> participating width of a one way slab under a point load.   Take TAN^-1(0.6)
> lines from the point load radiating to the supported sides of the slab.  For
> your case with a point load at the center, the participating width would be
> 2*0.6*11 = 13.2 feet.  Obviously, if the load is not at center span, the
> effective width will be smaller at one support than at the other since the
> slab cannot form a symmetric "saucer" shape.  I've always thought this was a
> little too optimistic for my comfort level though, and usually take no more
> than the point load width plus 4x the slab depth in width and provide extra
> reinforcing in this strip as necessary.  I'd be curious to hear how other
> people handle this situation, too.
>
> Regards,
> Joe McCormick
>
>

that too much (four feet wide )in my first respons I said only the point load
width  plus the the slab depth
or for max 2x slab depth  not more than that if i find the steel is too much
but the other queston you consider punching shear or not and what the area of
punching shear?

thanks

D.A.

```