Concrete Loading

[CADMAN169]

I'm in the process of placing a piece of equipment onto a concrete slab that is 8 inches thick on grade. I just had 2 core samples tested for compression rating. The results where 6800 and 9000 psi. The equipment that I'm placing weighs 94 metric tons. The equipment rests on the concrete from 26 7" x 3" pads. Will the concrete hold the equipment without failing? I was told by a structural engineer that it would not. He said the floor is rated at 500 lbs. per sq. ft. I'm not sure how he came up with that figure.

 

[Ussuri]

The thing about concrete slabs on grade is that it is actually the sub-base material which carries the loads. The concrete is effectively just a solid, smooth, wearing course. Based on the figures you gave (and a few assumptions, plus converting to metric);

Weight of plant 922kN - assume evenly distributed (probably wont be though) 922/26 =35.5 kN.

Support area 175mm x 75mm.

Pressure under footing = 35.5kN/175 x 75=2.7 N/mm2. Which is pretty low.

Punching shear around footing = 35.5kN/[2(175+75) x 200]=0.36 N/mm2. Also pretty low, so your concretes not a problem.

However, local bearing pressure 2.7N/mm2=2700kN/m2. For a very well compacted sand and gravel mix with SPT N values greater than 50, so its well hammered, you might get an allowable bearing pressure of, say, 800 kN/m2. A lot less than 2700kN/m2 so you one might say the soil will fail.

Rough as guts, but there you are.