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# Re: need help with slab

• To: <seaint(--nospam--at)seaint.org>
• Subject: Re: need help with slab
• From: "Craig Slama" <cslama(--nospam--at)hvc.rr.com>
• Date: Wed, 29 Nov 2000 21:06:19 -0800

```I agree with micheal...
one other possible discrepancies between the two models would be if the
T-beams you used to model the original slab spanned in only the long
direction, then this could increase your moments 80/60= 1.33 ...which is
amount of difference that you have in your moments...you should be able to
see if this is how it was modelled based on the edge conditions at the four
walls.

----- Original Message -----
From: "Michael Bryson" <bryson(--nospam--at)civil.ubc.ca>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, November 29, 2000 12:04 PM
Subject: Re: need help with slab

>
> 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
> answers for both methods although your method should be more accurate.
>
> 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?
> >
> >
> >
>
>
>
>

```