Suspended slab supported on three sides

[ataman]

Hi,

Can anyone give me some assistance in designing a slab on three sides?

I have a 7'-0"x15'-0" balcony and the architect does not want to have a front edge beam. I can either design as a cantilevered slab however I would like to keep the slab thickness to 6". I was considering cantilevering two beams but I'm not sure this will make much of a difference because of the aspect ratio. Can anyone give some advice on designing slabs supported on three sides and if this would make any difference.

Suggestions are also welcome.

Regards,
Adrian

 

[WillisV]

calculor - how to you propose that adding reinforcement at the end of the cantilever to create your "in-slab beam" makes this element any stiffer then the rest of the slab? Sure it might be a little stiffer due to the replacement of concrete with reinforcing but I doubt it would contribute enough to truly affect deflections in any appreciable way.

 

[ataman]

Thanks everyone for comments.

Tomfh...you are right that I am mostly concerned with deflections however savings in reinforcing steel for strength is also a benefit. While I believe that adding cantilevered beams on the 7'0 edge will help, I can't help but think the influence will be localised (ie a couple feet from the beam)since the aspect ratio is higher than 2. Do you have any source which illustrates your comments or is it something that you modelled?

The code limits cantilever thicknesses to L/10 unless you do more calculations. I'm going to take MYerges recommendations do a more detailed analysis for deflection.

csd72/jmiec....where can I find Rourke's formulas....is there a book that you recommend or an online source?

 

[miecz]

The book is "Formulas for Stress and Strain", by Roark and Young, published by McGraw Hill.

 

[csd72]

Look it up in the following website, it is in there somewhere

http://censoft.net/default.asp

 

[Tomfh]

Ataman,

We had the same situation (and the same argument) a few years back. I modelled it.