Truck Wheel Load

[ship4885]

I have to design a concrete slab, one-way, that acts as a loading dock floor and ceiling to a transformer vault. This slab must be designed for a uniform live load of 600 psf or a wheel load of 16kips, which ever causes the greater stresses, per the transformer manufacturers specs. The thickness of this slab is being controlled by shear based on a wheel load acting directly adjacent to the support, and also assuming the possibility of 2 wheel loads acting on the same strip at once.

Is there any reference as to how wide of an area I may distribute this wheel load over the slab? My boss had told me to reference AASHTO, but I cannot locate our office copy.

Additional slab information:
Span = 16'-0" clear
DL = 655psf
f'c= 4000psi
fy = 60ksi

Slab is designed as simply supported (true simple support on one side, dowels into support wall with #4 @ 10 on the opposite side)

I'd like to get the slab down to 16" but currently with f'c = 4000psi, I need a 20" slab, and this can be reduced to 18" with f'c = 5000psi, but my boss would like to stay with 4000 psi.

 

[JedClampett]

AASHTO has some simplified formulas for one-way concrete slab design. It would definitely be worth your time and the owner's money to go find a copy, even if you need to go to the local university or order a copy.
I don't have AASHTO in front of me, but even the 16 inch slab sounds too thick.

 

[bridgebuster]

If you have AASHTO Standard Specs go to Chapter 3 - I'm not in office today so I can't look up the subsection number.

 

[msquared48]

At 655 psf, why is your dead load so high? A 16" slab would be only 200 psf (WSD).

To distribute the forces, I have used the with of the tire plus the thickness of the slab to either side for the design strip width in the past. But, that being said, consult AASHTO.

Mike McCann
MMC Engineering

 

[ship4885]

Thanks for the replies, I will try to get a hold of the reference and go over their simplified procedure.

msquared48, there is a slopeing fill on top of this slab, plus a 4" concrete sidewalk topping on that. The sidewalk must be seperate from the slab with a waterproof membrane between them. In addition, there is an allowance of 30 psf for any hanging loads from the underside of the slab.

 

[ChipB]

See if your boss has a copy of Gaylord & Gaylord's, Structural Engineering Handbook. There is a section in there on bridge design and may help you out a bit. The 16k load on one strip sould be separated from each other by the distance of your axles.

 

[FeX32]

Gaylord!

Fe

 

[cap4000]

Check into H.M.Westergaard's 1930 publication which is part of the basis of the AASHTO slab design. Shear and moments are both tabulated depending on the span. The wheel loads spread out considerably. What bending moment are you coming up with?