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# Re: need help with slab

• To: seaint(--nospam--at)seaint.org
• Subject: Re: need help with slab
• From: Michael Bryson <bryson(--nospam--at)civil.ubc.ca>
• Date: Wed, 29 Nov 2000 12:04:13 -0800 (PST)

```You analyzed a 4" two way slab spanning 58'x82' to carry 287psf? The
bending moment of 68kip*ft/ft sounds about right in that case. And the
bending moments in the beams are probably close to 380 kip*ft.

I suspect what you have done is forgotten about the self-weight of the
beams and slabs when comparing the two methods. You should get similar

However, how do you check the deflections? I'm not sure that it works for
that case.

On Wed, 29 Nov 2000, Tomas Matta wrote:

>
> All borders are wall supported.  The slab is 4 in. thick.  The load is 1.4
> t/m^2 (287 lb/ft^2).  My boss wants to analyze it as a flat slab without
> beams, and then from the moments in the slab obtain the moments in the
> beams, meaning that if the max moments in the slab without beams are
> 68kip*ft/ft, the max moment that corresponds to the beam is
> 68*67/12=380kip*ft (67/12 is the spacing between beams).  The max moments I
> got were 567 kip*ft   Yes, I used SAFE to this.
>
> thanks again
> Tomas Matta
>
>
> Michael Bryson writes:
>
> >
> > Where are your wall supports? How thick is your slab? What is your
> > total factored uniform load? I don't understand what your boss' method is.
> > You say you analyze it as a flat slab without beams. Did you use SAFE to
> > do this?
>
>
>

```