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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.
• From: Neil Moore <nmoore(--nospam--at)spider.lloyd.com>
• Date: Mon, 29 Sep 1997 08:44:50 -0700 (PDT)

```><< 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 >>
>
>
>Joe, I don't understand the formula, is part of it missing?
>
>
>Tom VanDorpe, P.E.
>VCA Engineers

We encountered an engineer (old S.E.) who was promoting that approach a few
years ago (trying to justify placing a point load on an existing slab on
ground).  We couldn't accept it or rationalize it.

Neil Moore, S.E.

```