Concrete beam minimum steel 1

[EngDM]

Hey all,

I'm just wondering if CSA minimum steel for flexural members, clause 10.5.1.2 requires the reinforcing steel to be in the tension zone. The clause doesn't appear to indicate that it HAS to be tension steel (though obviously this is ideal); when using Jabacus today I noticed that their min steel check was based on the steel in the tension zone only.

I was under the impression that so long as the tension steel is designed for the loading, that the min steel was for the gross cross sectional area. Hopefully someone can confirm or point me somewhere that outlines it a bit more clearly.

 

[EngDM]

I know a retired super flat consultant

Hey I'm sure they're curvy where it counts...

The whole point is that the sub-grade is prepared so the slab doesn't. I know a retired super flat consultant who has designed 10s if not 100s of millions of square feet of super flat concrete slabs on grade used for high precision racking systems. His philosophy was always to treat the slab as paint on the sub-grade.

Interesting. So in saying that, is the assumption that as long as punching works then the slab is fine? There is a flexure check in the GRDSLAB spreadsheet and the Minnesota DOT has a paper outlining how to find flexural stresses for SOG which appears to be what the spreadsheet was based off of. That coupled with SAFE having an option to input a subgrade modulus and showing moments when analyzing strips is leaving me uncertain.

 

[EngDM]

The slab on grade in those cases in designed as plain concrete (see PCI method for example). If the slab on grade is designed as reinforced, then you provide reinforcement on both faces. If designed as plain concrete, the T+S is more optional that anything (have seen some plain concrete slabs, and personally I don't do more than 0.002 of the top 6" for plain SOG). You put the T+S on the top there because that is where the cracks are seen

Yea that makes sense. The context of this is more tenant fitup trying to get a slab to work for their intended use. If the racks were known prior I'm sure a different slab would have been specified since the loads are quite high per leg.

Got a link to PCI method? I tried a quick google and it brings me to precast institute, unless that is the correct spot?

 

[jerseyshore]

The whole point is that the sub-grade is prepared so the slab doesn't. I know a retired super flat consultant who has designed 10s if not 100s of millions of square feet of super flat concrete slabs on grade used for high precision racking systems. His philosophy was always to treat the slab as paint on the sub-grade.

I may be imagining it but I feel like there was a thread a week or two ago about why the GRDSLAB excel sheet doesn't take into account reinforcing of the slab. Very simple way of saying k value matters most.

I think I might open up a boardwalk T-Shirt shop with your best lines on here screen printed.

 

[jerseyshore]

Yea that makes sense. The context of this is more tenant fitup trying to get a slab to work for their intended use. If the racks were known prior I'm sure a different slab would have been specified since the loads are quite high per leg.

Got a link to PCI method? I tried a quick google and it brings me to precast institute, unless that is the correct spot?

I assume they meant PCA.