Concrete slab check for 60kN/m2 load

[ITV]

Dear Sir/Madam,
On top-slabs of a concrete basement, 60kn/m2 will be applied (racking systems plus forklifts). I would like to tell me your thoughts, based on your experience.
My first approach is 30cm slab, with shear reinforcement. Beams 70x70cm (see attached) I analyzed the system and I present you the results.

PS The footings of pallet-racking systems are big concentrated loads, that's why i am not thinking of any sandwich type slab.

Brief analysis results

https://files.engineering.com/getfi...4643-b093-befde683808c&file=Brief_Results.pdf

Extended results

https://files.engineering.com/getfi...-4851-ad30-a618f5bab773&file=Full_Results.pdf

 

[jayrod12]

60 kPa! that's 1500 PSF. That seems insane.

What's your grid spacing? I don't really see a better option than what you've developed. You said this was over a basement, I assume the outside line of columns, is actually a wall?

 

[ITV]

(the previously attached files give more details than this image)

 

[jayrod12]

Thanks, I'm not a giant fan of opening attachments to be honest. I'd rather the information be right in the post. It also made it seem like you may have attached a couple pages of calculations which I'm not generally interested in looking through. No offence meant by that, I'm just more here for high level looking.

That being said, I'm getting you needing roughly 4000 mm^2 of steel per metre of slab length at a rough go. Where I am that would be 25m @ 125mm o/c, seems bananas. Shear has to start governing as well right? You have almost 300 kN/m factored, You've got to be pushing the envelope on one way shear in some areas. But again, I've only run extremely rough high level numbers for gut checks.


For the beams I'm getting over 10,000 mm^2 of steel being required in the bottom layer. 10-35m bars would require a beam width of 860mm minimum to fit it all in the bottom layer. If it was in multiple layers, it would be less effective and therefore need more bars. That amount of steel also seems bananas. For a bit more depth of slab and beam, there could be a substantial reduction in steel amounts.

 

[ITV]

Thank you @jayrod12! Beams and slabs can be increased in depth of course. Don't worry, The results i attached are only images: is the required reinforcement, longitudinal in both direction and required shear reinforcements of the slab. Not calculations

 

[HTURKAK]

ITV (Civil/Environmental);

The design loads 79 kN per foot of rack and 60kN/m2 UDL seems overkill ..

Some typical, probable loads from EN 1991-1-1


- Imposed loads on floors due to storage Category E1 qk= 7,5 kN/m2 Qk= 7.0 kN.

- General storage qk= 2.4 per metre of storage height, Qk= 7.0 kN

- Traffic areas 30 kN < vehicle weight ≤160 kN qk= 5 kN/m2 Qk=To be determined but typical 20-30 kN



My suggestion would be , check the design loads again.








Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

 

[ITV]

There are 5 storeys of 3 boxes per span of 10kN per box. A 5% increase factor is applied due to the structure selfweight. And this is divided by 4 footings.

So its 5*3*10*1,05/4=39,4 kN per foot.

BUT: in worse case footings (middle ones), it becomes double: Here is the exact analysis of reaction-forces

The forklift weight is 4tons and the two boxes of 1ton that it carries, makes a 60kN. But you have right, the typical forklift area is larger than 1m[sup]2[/sup].

 

[rapt]

What is in the basement?

 

[ITV]

@rapt top secret maps that prove that earth is flat

 

[Italo01]

ITV, but is this load distributed uniformly throughout all the slab?

Because if you took the load of 157,5KN of the rack and the boxes and divided by the area, obtaining 60KN/m², this will be accurate only if the racks are all stacked side by side. A better approach would be to take the maximum number of racks on any slab, calculate the total load and then distribute, using the approach of using the footing load to calculate punching shear. Maybe you already did this to obtain the 60KN/m², so in this case, disconsider it.

 

[rapt]

If you want help, don't be a smart ass.

There is a perfectly good reason for the question?

What is the basement being used for?

 

[ITV]

@rapt: Forgive me, it was my humour. The basement will have an automation system with two small spiral conveyors, that lead to the "±0.00 level" floor.

 

[rapt]

Ok. So delivery/dispatch is to/from the basement and the conveyors raise/lower everything to/from the upper storage level?

Is it possible to reverse it? So the very high loads are on a ground supported slab removing support and deflection problems for the heavily loaded floor. And the automation system is above.

 

[ITV]

Unfortunately no. So i was thinking the slabs in between to be 30cm thickness in their upper part, and also their form to be like this: