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RE: Fork Truck on elevated slab

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Paul,

Thanks for that bit of advice.  Actually, this is what the owner required I
do.  That is why I have such a high force of the front axle.  It includes
the full weight of the truck plus the load.  Then I have a reference that
says I should add 30% for impact.

Rich 
 

-----Original Message-----
From: Paul Blomberg [mailto:blomberg_az(--nospam--at)yahoo.com] 
Sent: Thursday, June 02, 2005 9:48 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Fork Truck on elevated slab

This won't help you with the current concrete
thickness issues but you can simplify the problem by
placing all the load on the front wheels.  Having
driven a forklift in my college days, I know that I
would often load the fork truck up until the rear
tires would barely touch the ground.  Steering was
done by lowering the load so the rear tires would grab
and drag the load on the ground until the turn was
completed.  While you are not supposed to do this, it
is done often.

Also, if you are in a temporary situation where the
contractor only needs to lift 2,000 lbs. and the floor
can just resist the load but the fork truck is rated
for 6,000 lbs., have the manufacturer adjust the
hydraulics to limit the lift capacity to the desired
load.  It takes the manufacturers rep less than 30
minutes for the adjustment.  Trust me, whomever is
operating that fork truck will some day take it to the
load capacity limits.

Paul.
Phoenix, AZ



--- Rich Lewis <seaint02(--nospam--at)lewisengineering.com> wrote:

> 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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