Minimum Flexural Reinforcement ACI 318-19 8.6.1.1 for a very thick slab

[oengineer]

I have a foundation slab that is 4'-11 thick (the total dimensions are 14 ft x 14 ft x 4'-11" thick) & I am wondering if Minimum Flexural Reinforcement ACI 318-19 8.6.1.1 is applicable to this foundation. The applied vertical force is 100 kips & an applied moment of 295 k-ft. This is an equipment foundation.

Would it be accurate to consider Minimum Flexural Reinforcement ACI 318-19 8.6.1.1 or just insure that the shrinkage & temperature reinforcement requirements are met? The allowable soil bearing is 4 ksf.

Comments/suggestions are appreciated.

 

[slickdeals]

Your loads don't seem right.

 

[JoshPlumSE]

So, there is a flaw (IMO) with the ACI code for minimum slab reinforcement when compared to beams.

When you have reinforcement in a slab, you are required to meet the same flexural minimums that were developed for beams. These insure that there is enough steel to avoid a brittle failure when the beam cracks. However, for beams the code allows you to alternately provide 4/3 of the amount of steel required based on demand moments.

This alternatively is NOT allowed for slabs. So, you have to provide a lot more steel than is necessary (IMO) for thick foundation slabs to resist the loads applied to them.

Also, the Temperature / Shrinkage requirement of 0.0018 must be applied to both the top and bottom layers if they both need reinforcement. Meaning, the total minimum slab reinforcement often becomes 0.0036.

 

[HTURKAK]

My past experience ,
I have provided minimum 0.35 % flexural reinf . ( both ways total ) and additional 0.2 % top and perimeter cage rein. for shrinkage and temp.