Does Anyone Have Slab on Grade Example Calculations They Can Share?

[Tim_Crouse]

Hello Engineers

My background is in electrical engineering but I am helping to design an equipment slab (which will eventually be reviewed by a PE).

I have designed the slab using the PCA method and Back checked it with the GRDSLAB spreadsheet that is available online.

Does anyone have a set of worked calculations that may be shared related to a Slab on Grade Design? I would really like to brush up on the math behind the PCA
method and the GRDSLAB spreadsheet. User R13 (as well as others provided some guidance to the full set of calculations that should be performed in a situation like this):

-Basic Slab on Grade Calculation, Eg slab thickness and reinforcement requirements (primarily for crack control in this situation)

-Eccentric loading of the slab as only 2/3rds of the slab will hold equipment, the other 3rd is for future use

-Wind Loading on of Non-Structural Components

-Seismic Verification of the Designed Equipment Slab

If anyone has suggestions or design tips for slabs on grade please share
-For example, is there a minimum psi requirement for concrete when anchors will be embedded? I came across an article that 4,000 psi is required when embedding achors.
I never came across that before so it was a surprise to me.

-When dealing with a #57 aggregate subbase course how is the compaction properly defined on the prints as you cannot actually compact stone.
I currently have it defined as "Tightly interlock such that all excess volume is removed"

-When asking for the Soils Report should I request samples be taken at each end the slab will be placed to bring to light any issues that may be discovered when the soils reaction is calculated (I hope I stated that correctly)? Basically, how do I verify that slab will not sink at one end even if the placement detail calls for 95% compaction?

Thanks In Advance
-Tim C.

Sent From My TI-84+

 

[r13]

For your case, as stated in another thread, you won't need examples, as the design is quite straight forward. I suggest to use the allowable stress design method to minimize confusion. The steps,

1) Apply the equipment load as point/line load, with moment due to lateral load effects (wind/earthquake).
2) Use limit equilibrium method to derive soil pressure (note, ignore slab weight, and/or any uniform load).
3) Treat the concentrate equipment load as support, and draw shear and bending diagrams due to soil pressure.
4) Check shear strength of the concrete per ACI provisions for plain concrete.
5) Check bending moment - obtain maximum tensile stress in concrete, if it is less than the allowable concrete rupture stress, then you won't need flexural reinforcement, but to provide temperature and shrinkage steel for better crack control (check ACI318, or ACI350). Otherwise, conservatively apply load factor, 1.5, to the non-factored design moment and design per ultimate strength design method.

There is no rigid strength requirement for concrete with embed anchorages. But you need to follow App. D of ACI318 to check the strength of the embedment and the concrete. 4000 psi compressive strength is quite common in practice these days.

To achieve a well compact subgrade, well graded backfill is superior to uniformly graded (single size aggregate). Again, you shall consult with your geotechnical engineer on this.

For wind and seismic loads, you need to check the respective provisions per IBC. The wind is a little tricky on your case though (4' to adjacent walls on all sides). Let's see if someone else has good suggestion.

 

[bridgebuster]

I posted some cacluations recently; they may be of some help.

Link