Control joint spacing of slab on grade in open air parkingstructure

[ajk1]

What is the maximum spacing of control joints in 125 mm thick slab-on-grade open air parking garage in Ottawa Ontario Canada climate. I feel that 36 times the slab thickness for a 125 slab = 4500 mm (15 feet) is too far for a salb subject to external environmental temperature changes. I realize that the actual spacing will generally be governed by the column spacing, but what would be the "maximum" permissible spacing to avoid excessive cracking?

 

[BadgerPE]

I was always taught that they should be spaced at 2-3 times the slab depth (joint spacing in ft/slab thickness in inches). For a 5" slab, the top range of the ratio would be 15'. I usually recommend closer to 2.5 for exterior slabs. So in this case, I would use a 12'-12.5' spacing.

I am unsure if I have ever seen this spacing codified, but rather I learned it from a professor who is a paving "expert". So take it for what it is worth.

 

[Ron]

ajk1...rule of thumb is 24 to 36 times the thickness. You are at the upper end. Lower end would be about 10 feet.

125mm is pretty thin, so I would go close with the spacing...10-12 feet

 

[ajk1]

Thank you both, Crackerjack and Ron. I would have said similar to what you said. I have to look up what I did in several garages I designed about 10 years ago, but I suspect I have used both 10 and 15 feet. In the latest case that we are designing, the garage is in Ottawa, where the winters may be more severe than here in Toronto, I would be inclined to go not more than 12.5 feet and not less than 10 feet. If the column grid is at 30 feet, then the joint spacing would be 10 feet. Thanks again to you both. Much appreciated.