We are designing a slab on grade for an industrial occupancy with moderate
fork truck loading. We have used the PCA-type approach as outlined in Ringo
and Anderson's book. We have used the Subgrade drag equation for the basis
of calculating steel area in slab.
F L w
As = --------------
The value of L is the slab length between free ends which we have assumed
is the distance between construction joints. We have detailed a formed key
at the construction joint with no steel running through. The slab is
thickened at these locations to account for the effects of loading at a
non-continuous edge. In our case we were using 10M (little bigger than #3)
at spacings to suit the value of "L".
1. We design thickness for loading on the interior of the floor slab. What
about the control joint locations. Would not a sawcut of 1/4 depth be
treated as a dowelled joint therefore causing the slab to require
thickening at all control joints? Because of this you would end up treating
the entire slab as being partially unsupported because the suggested
tapering for thickness changes is 1:10.
2. At free ends we used slab thickening with a formed key with no steel
running through. Any comments? The frequency of the construction joints is
almost dictated by a reasonable amount of reinforcing. This seems to be
construction joints that are a little too close (70' to 100'). Any thoughts?
3. I just received a call from a manufacturer of steel fibres. They sound
great but I have not used them before. The most important thing in this job
is too have NO cracking as this is replacing a cracked floor that was
constructed not too long ago. Has anybody had any negative experiences
using the steel fibres? They are suggesting the total replacement of the
steel with the steel fibres.