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Related Articles


punching shear in basement slab

punching shear in basement slab

punching shear in basement slab

I am trying to convince the homeowner to let me drill a small hole in their slab so I can verify the slab thickness in an area where a lolly column has to be added. Normally only the original areas where the lolly columns are placed get a thicker footing ex. 6", then the surrounding areas get reduced to 4" where no support is being placed. Does anyone know of a quick reference I can refer to for punching shear. A 5x5 steel plate will deliver a point load of 8600 pounds through to the basement slab. Want to know what the minimum slab thickness should be on 1960's concrete, most likely no reinforcement. F'C is probably 2500 psi.


RE: punching shear in basement slab

My handy dandy spread footing chart from the 1963 ACI specifies a 10" thick 36" square pad for a load of 9 kips reinforced with 3 #4 each way. I would never want to put a 9kip load on a slab on grade that's only 6" thick.

RE: punching shear in basement slab


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