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False Floor Shearing Stress

06/14/2012 3:43 PM

Hi Guys,

Was wondering if you could help me out here. One of the casinos that I run had a flood a while back which caused the false floor tiles to rot and warp. We now have to redo 1000m² of panels costing $27,000. The proposed panels are concrete, we had composite wood ones before that worked fine until we had the flash flood. We are working on a solution to prevent this from happening again, so water shouldn't be an issue again.

How can I justify using 1 inch thick 2' x 2' plywood panels (Which are cheaper), as oppose to the concrete tiles of the same dimensions. We had composite wood ones before with the same dimensions, and in my opinion plywood is stronger than composite wood and can absorb moisture without warping too much.

This extra money that could be spent is much needed in other venues in the casino.

Any advice here would be greatly appreciated. Thank you in advance.

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#1

Re: False Floor Shearing Stress.

06/14/2012 3:57 PM

This is fairly simple.

Let's think this through... If there is a confidence, if you have a real firm belief, that the "... solution to prevent this from happening again..." is a true solution and it won't happen again, then the floor covering can certainly remain wood.

However, if the solution is a little wobbly, you are only pretty sure a water event won't happen again... you should consider the concrete panels as part of the solution.

Prevention versus mitigation.

You said "We had composite wood ones before with the same dimensions, and in my opinion plywood is stronger than composite wood and can absorb moisture without warping too much." I would investigate, rather than act on uninformed opinion.

Where does shearing stress come into this? Have I answered the wrong question?

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#4
In reply to #1

Re: False Floor Shearing Stress.

06/14/2012 6:37 PM

Hi Doorman,

Thank you for the response. Yes there is a void under the floor of 50mm to house condiut and raceways. The force exerted on a square meter would be around 120lbs, however when we drive a car over the floor for promotions it would be substantially more. What I am trying to figure out is what resultant force would it take to break a panel off the guides on each side of the square. Here is what I have:

Panel Size: 24" x 24"

Panel Thickness: 1.5"

Height of Panel (Void Space): 2.5"

Support Beams Thickness: 1.5mm U-Tubing with U facing downwards

Support beam contact width area on panel per side: 20mm

Support Beam material: Galvanized Mild Steel

Panel Material: Composite (Pressed) Wood

Please assume the wood is dry, I did learn how to calculate this back in Tech, however it has been a while and I can't seem to figure it out accurately. Would you know the tensile strength of composite wood versus plywood versus concrete.

I would really like to have some solid information with a formula proving that the plywood is stronger than the composite wood, what the shearing force would be on the floor for all of them, and how going the concrete route is a bit extreme.

Thanks guys for all your input so far, it is much appreciated.

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#2

Re: False Floor Shearing Stress

06/14/2012 4:46 PM

You are probably correct that plywood would be stronger than composite wood panels.

You are definitely correct that plywood would stand up better to water.

"False floor tiles" implies raised access flooring. Is this true?

If so, will the patrons be walking on this flooring ?

If so, You must use materials specifically engineered for the purpose, or have calculations performed supporting your selection of plywood.

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#3

Re: False Floor Shearing Stress

06/14/2012 5:28 PM

Casino? $27,000.00?

Sounds like a crap shoot to me.

Throw the dice and go with the wood, if it is suitable for that purpose.

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#5
In reply to #3

Re: False Floor Shearing Stress

06/14/2012 6:40 PM

LMAO!

I agree, just need to have something solid (Pun intended) for the C.E.O. to back me up.

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#6
In reply to #5

Re: False Floor Shearing Stress

06/14/2012 7:25 PM

I agree, just need to have something solid (Pun intended) for the C.E.O. to back me up

Well you could always print out our CR4 responses and include them in your proposal.

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#7

Re: False Floor Shearing Stress

06/14/2012 7:59 PM

Robotech,

Cement filled raised\access floor tiles are designed with high shear and point load ratings and are designed for Static loads.

Composite tiles are designed for Rolling load and will handle your cars being moved around much better, the steal shell on the back side which wraps around the sides is designed to maintain the integrity of the tile against the shear force of the edges which are the weakest points.

Replacing the tiles with laminated timber or plywood will Not be viable without steal backing to cater for the shear force. The pedestals will punch through the timber and the stringers will shear the edges of the timber.

Cement Filled Tiles: -

  • Point load = 6kN/25mm
  • Dynamic or Rolling Load = 5.5kN with 25 X 75mm Rollers (10 Passes)
  • Final Loading 18kN/25mm.
  • Impact Loading 68kg

Composite Tiles: -

  • Point load = 5kN/25mm
  • Dynamic or Rolling Load = 4kN with 45 X 75mm Rollers (10 Passes)
  • Final Loading 15.5kN/25mm.
  • Impact Loading 45kg

I do not have figures for Plywood, but unless you use Marine Grade, I don't believe will handle the spilt drinks and steam cleaning that is often required to maintain casino and pub environments.

I definitely do not believe that plywood will offer the same performance as properly design access floor system tiles.

The designers selected the floor for a reason, I would be focusing on making sure that water in never an issue in the future and or go with the cement filled.

Also it is good practice to use "sacrificial" running boards to move heavy loads across raised access floor to spread the load and increase the life of the system.

Regards,
Sapper

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#8
In reply to #7

Re: False Floor Shearing Stress

06/15/2012 3:27 PM

Hi Sapper,

Thanks a million, very impressive answer there!!!

Thanks again to everyone for your input, much appreciated. Hope you are all well.

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#9

Re: False Floor Shearing Stress

06/16/2012 4:41 AM

Sapper has given you the good oil here mate.

Your original floor material (and the support for it) sounds like an improvised solution in itself.

What's your jeopardy if the floor fails while rolling a car around on it? Crushed cables, toppled gaming assets,..... the losses could be very high. The house can't lose right?

Instead of impressing the CEO with a cheaper floor tile solution that might work, impress him/her with a costlier solution that is guaranteed to work.

What was the source of the flood water previously?

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Users who posted comments:

Doorman (1); jack of all trades (1); lyn (1); Robotech (3); Sapper (1); Wal (1); WJMFIRE (1)

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