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RE: Payloader Slab Design

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Ed,

The AASHTO is not necessarily appropriate for heavy wheel load traffic.  

I have seen AASHTO HS-20 used to design fire fighting platforms on the top
parking decks, and the slab thickness is not even close to take outrigger
loads from an aerial platform.

I would recommend:
1.	Determine the loading according to the manufacturers wheel and axle
load specifications.   
2.	Distribute the loads referencing "Designing Floor Slabs on Grade" by
Ringo and Anderson, Chapter 3 Design for Vehicle Axle Loads, section 3.2.
Distribute the loads to create a worst case for shear, and a worst case for
moment.

Obviously the shear will drive the thickness, then move the loads to create
a worst case for moment.

Regards,
Harold Sprague



> -----Original Message-----
> From:	Ed Fasula [SMTP:tibbits2(--nospam--at)metro.lakes.com]
> Sent:	Monday, April 17, 2000 10:40 AM
> To:	seaint(--nospam--at)seaint.org
> Subject:	Payloader Slab Design
> 
> How would one appropriately design for heavy equipment loads on a concrete
> slab? 
> 
> We have a grain storage building with a 4' reclaim pit over which a
> reinforced concrete slab will span.  Is using AASHTO moment formulas
> (sections 3.24.3.1 & 2) and scaling for a 86 kip Payloader (with impact),
> appropriate?  It seems the Payloader wheel distribution would be
> significantly different from a HS 20 truck.  Using 3.30, Tire Contact
> Area, assuming 40 kip on each wheel, A = .01*40,000lb = 400 in^2, which
> gives length = 31.6" and width = 12.7"  which seems in the ballpark...
> 
> 
> Also, AASHTO 3.24.4, which states that shear would not need to be checked,
> seems to be a clearly inappropriate assumption to make in this particular
> situation.  But what would the assumed shear distribution be, 12.7"?
> 
> Thanks in advance for any help.
> 
> Ed Fasula, E.I.T.
>