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RE: Slab Transition Detail

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Bob & Harold,

 

Thanks for the responses.  You asked some good questions.

 

Right now, I’m stuck with the aluminum wheels.  It’s an addition to an existing industrial facility and the carts are in use.  They tell me the reason for the aluminum is because the carts are placed in a bake oven and heavy loads.  I’m not sure why that matters, but when I asked why aluminum, that’s what they told me.  They told me later they had used steel wheels in the past but the steel wheels chewed up the slab so much they changed to the softer aluminum.  I haven’t seen them in operation, but apparently they push these carts around on the floor using a fork lift.  They pick up one side and roll the other.  The slab surface is chewed up pretty good.  So are the aluminum wheels.  I’m wondering now if the aluminum is causing the surface of the concrete to deteriorate even more. 

 

The steel plate is at a steam bath area.  Motor casings are placed on these carts and one of the processes is steam cleaning.  The cart is positioned on a steel plate over a pit.  One plate is perforated to allow water to drain into the pit.  There is a plate bolted to the slab in front and behind the pit as an approach to pit.  The 3 plates are approximately 5 ft. x 10 ft.  Right now the approach plate sits on top of the slab and there is a bump as it rolls.  Originally the pit area did not have approach plates.  The approach plates were added because the concrete slab was chewed up really bad in front and behind the pit. 

 

The first thought was to repeat the design in the new addition.  I was going to have the plate flush with the top of slab.  I don’t think it is possible to float a plate that big during a pouring operation of the slab without getting voids under it.  The plate needs to be installed after the slab is placed.  The constant moisture would eliminate any wood planking consideration.

 

I’m now thinking that the extra approach steel plates probably should not be required if the concrete was designed adequately around the pit, and there was a good armor joint like Harold suggested.  I looked at the PNA armor joint, and one by Kalman.  I’m thinking the slab surface should slope towards the pit and have an armor edge around it.  The top surface of the plate over the pit would match the armor edge of the concrete.  The concrete should have a dry shake surface hardener.  I’m a little hesitant about this though since they have experienced problems with the slab around the pit in the past.  Although, it was never designed for that kind of use in mind when the original slab was poured.

 

Any other suggestions for this design would be appreciated.

 

Thanks.

 

Rich

 

 

 


From: Robert Kazanjy [mailto:rkazanjy(--nospam--at)gmail.com]
Sent: Thursday, March 01, 2007 7:09 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Slab Transition Detail

 

I assume you're stuck with the aluminum wheels?

What are the wheel loads?   Frequency of travel?

This could be a real problem......I know of situation where a slab was designed for "forklift traffic".

Unfortunately the designer thought "pneumatic tires" but these were little warehouse forks with rubber over steel wheels....add to this some slab curl at construction joints and you wound up with forks destroying the slab at these joints   :(

You are wise to think about this now but with more details I really can't provide much help.

If the carts / wheels need a steel wear surface, why are they ever leaving the steel?

Any imperfections will be magnified as the load pounds the transition......compliant materials are your friend but the load has to get onto the concrete eventually. 

Maybe design it with maint / replacement in mind?  Like the rubber stuff at street / railroad intersections?

CalTrans' info about bridge joints might be of some use.

>>>
Would chamfering the edge of the plate help at all?<<<<,

Yes but again you're transitioning from a damage tolerant, strong, ductile material to concrete (all its not)

I'd warn them that stiff metal wheels are going to be hard on the concrete at the transitions.

cheers
Bob

On 3/1/07, Rich Lewis <seaint04(--nospam--at)lewisengineering.com> wrote:

I have a condition where a steel plate will be embedded in a concrete slab.  The plate will be about 1/2" thick and provide a hard wearing surface for solid aluminum wheels on a cart hauling heavy equipment.  The dimensions are 10 ft. x 4 ft. 

 

I am wondering about the edge condition of the plate and concrete.  The wheels will roll over the edge from concrete to steel.  Should this be given special consideration?  Would there be a tendency of the concrete to spall around the edge?  Should a joint be put around the edge and filled with semi rigid epoxy filler? Would that still tend to spall from the wheel load?  Would chamfering the edge of the plate help at all?

 

Thanks for your help.

 

Rich