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RE: Fork Truck on elevated slab

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James,

 

Thank you for your response.  It was very helpful.

 

I have done some more research.  I was not able to get a full copy of the Bulletin 80 I previously mentioned.  I was able to find a good example problem on US Deck web page http://www.njb-united.com/usd/examples/example3.pdf  I was told this example problem is similar to the method outlined by the Steel Deck Institute publication.  This is the most detailed illustration I could find.  They treat effective width differently for shear and bending.  The effective width is based on how far away from the support the load is placed.  That makes sense to me since the closer the load is to the support, the less it can distribute out.  For my design, and I guess most designs, the critical shear occurs when the wheel is adjacent to the steel beam and the fork is running parallel to the beam.  The double wheel load is now in shear.  The downfall of this is that the second wheel, the one furthest away from the beam, should have a wider distribution then the inner wheel, the one closest to the beam.  I haven’t found any guidance for how to reduce the outer wheel load.  If I use the effective width based on the closest wheel I get a slab thickness of 12.5” for shear.  I was thinking it should be less.

 

Rich

 

 

-----Original Message-----
From: Kestner, James W. [mailto:jkestner(--nospam--at)somervilleinc.com]
Sent: Wednesday, June 01, 2005 11:00 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Fork Truck on elevated slab

 

Rich:

 

It is not advisable to use a composite metal deck to support loads from fork trucks. As previously stated, the deck will become debonded from the concrete. We recommend a minimum of a 6" formed slab with top and bottom layers of reinforcing in each direction.

 

The effective slab width for computing bending will depend upon the contact area of the wheel load. A conservative effective width for bending would be 0.6 times the span, as long as the wheel load is not near a free edge. It is recommended that all edges be supported. Please note that this effective width is only for monolithic concrete slabs.

 

One very important point that cannot be overlooked, is that the overlapping stresses from adjacent wheel loads must be taken into account. If the the spacing between wheels is less than the effective width as described above, than it should be reduced to 1/2 the wheel spacing plus 0.25 times the span.

 

If two trucks are able to pass (for example, in an aisleway) than that would further reduce the effective width in a similar way.

 

It is important that bottom distribution steel (generally more than temperature & shrinkage steel) be provided at right angles to the main steel. It can be calculated similarly to a column footing with concentrated load(s) being spread out to the effective width.

 

Good Luck!

 

Jim K.

 

 

 -----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc]
Sent: Monday, May 30, 2005 5:56 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Fork Truck on elevated slab

Rich Lewis wrote:

The question I have is the effective width for slab to check the shear and bending.  Putting all the force in a 1 ft. wide strip for shear is overkill, but how wide is best?  Also, right now I am intending to use a slab on metal deck.  How to treat this verses a solid slab is also an issue.

Do you not just compute the punching shear strength of a prism of concrete whose small end is the loaded area?

Conservatively, the bottom of the prism is at the TOP of the metal deck. Again, conservatively the metal deck is not considered to contribute to the punching shear strength (although we know that's not true; a metal deck contributes a great deal especially in and through its in-plane stiffness).

(Still think I'm missing something vital in your question. If so, I apologize).
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