# construction joint spacing for SOG

• To: seaint(--nospam--at)seaint.org
• Subject: construction joint spacing for SOG
• From: David Handy <dhandy(--nospam--at)trg.ca>
• Date: Thu, 04 Jan 2001 11:19:42 -0500
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 = --------------
2   fs
```
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".
```QUESTIONS:
```
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.
```
David Handy, P.Eng.
dhandy(--nospam--at)trg.ca

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