one way slab supported on beams 2

[ajk1]

Does anyone know of software or spreadsheet that will calculate the design moments at the face of supports and at mid-span for a multi-span one-way slab?

I usually do this be coefficients (WL/11, WL/16, etc.) but occasionally need something more accurate. In the old days, I would do it by moment distribution, and take account of the haunched ends, and reduce moment to face of supports, but am now too old and tired to do this ...today there must be software around to do this.

 

[JAE]

I haven't found anything that does concrete beam design like I'd like it to do.
Years ago I wrote a DOS program that allowed multiple uniform and concentrated loads, alternating LL, column stiffness, etc. it was very fast (13 spans analyzed and designed in a few minutes. As archaic as DOS was it was way faster than any windows based software today.

If you find anything good, post it here. I'd be interested.

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[KootK]

spSlab and spBeam by PCA



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[msquared48]

You know, every once in a while I like to go back in time and solve things by hand. It helps to keep me sharp and have an alternate means of solving problems when the power goes out.

Mike McCann, PE, SE (WA)

 

[KootK]

This is another good option: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[ajk1]

We have our own in-house program for concrete beams which we have developed over the last 40 years. It is super good, and I could certainly use it to analyze the slab, but I thought that there might be something simpler that applies to one-way slabs only, but that would account for pattern live load to find max moments, and also for the haunching effect of the beam support. The PCA slab program is intended for more complex slabs, and I expect that the input is more voluminous than it would need to be for a simple one way slab that I described above. If not, looks like I would have to further develop the spreadsheet that I wrote a few years ago for moment distribution.

 

[KootK]

PCA slab can certainly do more complex things but, once you elect a one way design, the extraneous input disappears. You get patterned loading, rebar cut offs, sexy graphical presentation of moment and shear diagrams... Seriously, it couldn't be much simpler without just devolving back into the direct design method (which I also like very much).

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BAretired]

Moment coefficients are probably as accurate as is required for one way slabs. A computer program is not going to yield accurate results unless it considers the deflection of the beams along with pattern loading.

BA

 

[ajk1]

If all the beams deflect essentially the same amount, I am doubtful that the beam deflection would have a significant effect on the one way slab moments, would they?

If what you say Kootk about the extraneous input disappearing, then PCA slab design seems to be the way to go (except that I would have to buy it!). I never liked the direct design method and as far as I am aware our office has rarely if ever used it. Seems to be a method that was grandfathered in from the old erroneous empirical design method (with some changes that tried to address the major error of the old empirical design method, that it did not satisfy statics); also has restrictions on load and ratio of adjacent spans that sometimes preclude its use.

Thanks all for the info about PCA Slab, and all the thoughtful comments. Much appreciated.

 

[BAretired]

If all the beams deflect essentially the same amount, I am doubtful that the beam deflection would have a significant effect on the one way slab moments, would they?

If all spans are identical and all beams are loaded equally, deflections will be the same; if spans are not identical, deflections will vary; if pattern loading is considered, even if spans are equal, loaded beams will deflect more than unloaded beams. In a storage building with large live loads, it could make a considerable difference.

BA

 

[ajk1]

Agreed. Thanks.

 

[rapt]

RAPT, for RC and PT slabs and beams!

 

[JAE]

Actually - the outer (exterior)spans have higher deflections than the interior spans under uniform loading.

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[saaveze]

Have you tried RisaFloor? With the help of you tube videos, I found it relatively simple to use to check a two way slab design and I know there is a function for one way slab also.

 

[ajk1]

Hi Saaveze - does RisaFloor account for the haunching effect of the supporting beam? In other words, if there is an 8" thick slab supported on a 48" wide x 20" deep beam, does it include the haunching effect of the beam on the slab? Is there a cheap version of this software available?

Hi RAPT. What is RAPT? Is it a program that will analyse slabs?

 

[hokie66]

ajk1, just google it. RAPT is the most used concrete design software in Australia, and I think is available in several codes.

 

[ajk1]

Hokie66 - ok, thanks for letting me know. I will look into it tomorrow. I am just about ready for sleep here.

 

[dcarr82775]

I would look at spSlab as KootK mentioned. It is dirt simple and quick to use.