Line Loads on Unreinforced Slabs
Line Loads on Unreinforced Slabs
(OP)
Can anyone point me in the right direction for information relating to line loads on unreinforced slabs.
I need to check the adequacy of an existing domestic insitu ground bearing slab with a load bearing structural stud built off it. This is lightly loaded but I would like some further guidance on how I could justify the slab is adequate (or not).






RE: Line Loads on Unreinforced Slabs
RE: Line Loads on Unreinforced Slabs
When you talk about designing it as plain concrete obviously the shear at the face must be less than
0.8 x Root Fcu
what other checks would you do (bending etc.) bearing in mind the slab is relatively long and shallow? Or would you just distribute the load through the slab and get the bearing width at its underside then ensure the pressure in this width is significantly less than the bearing pressure?
RE: Line Loads on Unreinforced Slabs
In residential construction, it common for the slab thickness to vary from 1" to 6". Also interior slabs frequently get poured (not placed) over uncompacted soils or construction debris because of the construction process.
Have a few holes drilled in the slab and probe with a wire to determine the real slab thickness and the existance of any soil supporting the slab.
If you find a questionable situation, just cut out a strip of the floor and build a proper strip footing on comapcted fill.
You cannot assume anything when it comes to basement constuction.
RE: Line Loads on Unreinforced Slabs
It's titled "Concrete Floor Slabs on Grade Subjected to Heavy Loads." Appendix B has a method for calculating wall loads on a slab.
RE: Line Loads on Unreinforced Slabs
RE: Line Loads on Unreinforced Slabs
RE: Line Loads on Unreinforced Slabs
thanks, Dik
RE: Line Loads on Unreinforced Slabs
RE: Line Loads on Unreinforced Slabs
With a 2X4 plate, that load is spread out to a width of only 3 X 3.5" = 10.5". So, the resulting stress to the underlying strata is more than that seen by the slab. You will need a soils report to verify soil bearing values of the range of 4 to 5 ksf.
Therefore, the major problem here will not be the slab, but the capacity of the underlying subgrade to bear the load.
I agree with the above comments to check the underlying strata and slab thickness.
Mike McCann
MMC Engineering