Warehouse Slab Design - Dowel-less joints
Warehouse Slab Design - Dowel-less joints
(OP)
We have a warehouse with light forklift traffic and a Contractor that has a lot of experience and success with placing 6 inch slabs, unreinforced and control joints at 12.5' oc without dowels with other engineers.
I'm fine with the plain concrete and joint spacing, but in my experience, I've always provided dowels for load transfer with wheeled traffic.
For the life of me, i cant find a reference for eliminating dowels for this type of loading. Does anyone have a reference or any helpful hints?
I'm fine with the plain concrete and joint spacing, but in my experience, I've always provided dowels for load transfer with wheeled traffic.
For the life of me, i cant find a reference for eliminating dowels for this type of loading. Does anyone have a reference or any helpful hints?






RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
You do really need to keep the slab offsets to an absolute minimum. That other warehouses didn't report problems when the owner took over from the construction contractor doesn't mean there are no problems now, in the future, or problems that aren't reported from the forklift operators to the forklift foremen to any forklift supervisors to any previous operating managers to any previous executive officers to any previous owners back to this particular contractor, who wants to report to you that "there have been no problems in previous jobs".
That's a lot of filters between the guys who have to slow down at each joint and the contractor who doesn't want to put in dowels.
RE: Warehouse Slab Design - Dowel-less joints
Don't forget about the building columns. Forklift drivers LOVE to hit those!
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RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
@MotorCity - dowels are provided at control joints for load transfer in slabs subjected to wheel loads. Refer to the Army Manual CONCRETE FLOOR SLABS ON GRADE SUBJECTED TO HEAVY LOADS pg 5-12 fig 5-6 and ACI 360R-10 figure 6.5.
http://armypubs.army.mil/epubs/DR_pubs/DR_a/pdf/we...
I've since come across "aggregate interlock" in ACI360. Does anyone have experience with this?
RE: Warehouse Slab Design - Dowel-less joints
The statement which is incorrect is your opinion that dowels are only used at construction joints, not control joints. This is clearly inaccurate in industrial slabs, which need a better mechanism than aggregate interlock.
All that said, I think joints in slabs at 12.5' centres will soon be a thing of the past. "Jointless" slabs are being used more and more. The main advantage is in reducing maintenance costs.
http://northrop.com.au/201704/big-pour-australias-...
RE: Warehouse Slab Design - Dowel-less joints
TNT would disagree with fibre reinforced pavements.
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
Me either. The only time I use dowels is at construction joints.
RE: Warehouse Slab Design - Dowel-less joints
If subgrade is "good" and correctly prepared... plain concrete, with or without dowels, will likely work just fine.
Or, as with most of my projects, if subgrade material is a "compromise" (but well prepared), even reinforced slabs, with dowels everywhere can have a hard life.
www.SlideRuleEra.net
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RE: Warehouse Slab Design - Dowel-less joints
It seems you're relying on aggregate interlock.
RE: Warehouse Slab Design - Dowel-less joints
I figure the steel (in the slab) by the subgrade drag equation, then (as far as thickness goes) I will figure the moments & shears developed based on (assuming we are talking about forklift traffic) the load being near a edge or corner (which almost always controls) and compare that to the modulus of rupture and the shear capacities of a preliminary slab thickness (selected based on wheel load charts in ACI 360).
The corner and edge calcs I do with a program like STAAD (I have a generic file set up to do it every time; I just alter the subgrade spring constants and the loads from job to job).
As an alternative, I use to use a old concrete text by Winter & Nilson that has equations for point loads on slabs at those critical locations.
As far as the "aggregate interlock" question goes.....yes, I do use it. I've heard a lot of arguments against it....one being that the slab will curl and wheeled traffic hits the edge of the curl and cracks it.
Well my answer to that is: if it's going to curl....it's going to crack in a lot of places (from traffic and so forth) regardless of what you've got at the joints. A lot of times, that's as much as a QC issue as anything.
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
Very bad cracking on the floor, to the point of it being unserviceable.
I believe there is a report on this somewhere (Len Stevens ex professor Melbourne University was the author).
I would never use fibre reinforced concrete and I believe many other designers would also not touch it.
I recall there was a thread on this years ago.
I also never have specified dowels in saw cut joints, just let the fabric go through. Only use dowels (round dowels) at construction joints.
RE: Warehouse Slab Design - Dowel-less joints
It is certainly a specialized area at the moment, but steel fibres in concrete have lots of advantages if done right. Now, if the case you are thinking about used useless plastic fibres, I won't try to find the report.
RE: Warehouse Slab Design - Dowel-less joints
SRE nailed it though: the base is everything!! I drive on unreinforced concrete highways every day.
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
http://www.concretepavements.com.au/Documents/16%2...
RE: Warehouse Slab Design - Dowel-less joints
Half our work seems to be dealing with busted joints.
RE: Warehouse Slab Design - Dowel-less joints
RE: Warehouse Slab Design - Dowel-less joints
All of our control joints are sawn to 1/4 of the slab thickness, with the reinforcing continuous through it (most of the time, unless its very heavily loaded and has a top mat of rebar).
RE: Warehouse Slab Design - Dowel-less joints
For reinforced slabs, you are right, but the OP's question concerns "...slabs, unreinforced..."
www.SlideRuleEra.net
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RE: Warehouse Slab Design - Dowel-less joints
Is it as simple as using the PCA nomographs for interior condition?
Im not concerned about my free edges and corners as i will have thickened slab edges, reinforcing and/or the loads will be sufficiently far from the perimeter.
RE: Warehouse Slab Design - Dowel-less joints
I might backcheck it with PCA charts.....but with the "rack loads" you are likely not going to have a pattern that matches the charts......ergo in such a case, I'd use a FEA program.
RE: Warehouse Slab Design - Dowel-less joints