Integrity Steel in Two Way Slabs

[MagicFarmer]

I am currently working on the design of a two way slab. I have been using spSlab (Structure Point) for this. I am currently reviewing the design output for integrity steel at the columns and the numbers are very high. I discovered that the program is including the service loads from the steel columns above (directly over the podium columns) in the loading used to calculate the amount of integrity steel required.

My understanding of integrity steel was that it is meant to take the punching shear force from the slab. IN CSA A23.3 we have "Vse = shear transmitted to the column or column capital due to specified loads, but not less than the shear corresponding to to twice the self-weight of the slab." Does this imply the service loads from the column above should be included?

Thanks,
MF

 

[atrizzy]

Sounds like an issue with the program. I would not include service loads from point loads concentric with the column. I believe the purpose of the integrity reinforcing is to have enough tension capacity in rebar after a punching shear failure to support the dead load of the slab alone and avoid it collapsing onto the floor below.
I believe the 2Vse is intended to (roughly) represent the dead load of the tributary slab area, but somebody can correct me about that if I'm wrong.

 

[rapt]

Agreed, it should only be the load from the slab, not from columns above directly loaded on the column.

 

[hokie66]

Agree with rapt, but be careful with the connection of the steel column to the concrete, ensuring that any depression does not affect the punching shear capacity. Often, an architectural requirement for setting down base plates can lead to loss of slab depth and displacement of reinforcement.

 

[KootK]

I'm confused as to how a column load was even input. Is SPslab not a strip / equivalent frame program? I wouldn5 think that you'd have column loads from above unless you went out of your way to put them there.

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.

 

[MagicFarmer]

Thanks everyone! I was under the impression that the column load above should be discounted because the definition of Vse revolves around the "shear transferred to the column," and not the "load transferred to the column." spSlab threw me off and got me thinking down a rabbit hole though.

@KootK, there is a place to include column loads and displacements so that you can simply take the column load output data and move on to use it as input in spColumn.

Thanks again,
MF