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Re: Truck Axle Loads

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Here's a bit of trivia.  It depends on the service requirements, and whether
or not you need to consider loadings beyond AASHTO HS-20.  "Real" loads can
be very different than AASHTO loads, and for after-the-fact analysis of
existing bridges this leads to the Manual for Condition Evaluation of
Bridges (AASHTO), and the consideration of "inventory" and "operating" load
cases and criteria.

For new design of a slab subject to highway truck traffic, I would pursue
getting copies of scale tickets from the trucker and/or various shippers who
could be future users of the load/unload station.  It may be worthwhile to
look at the load ratings of the tires and configuration of the equipment in
use.

Mark D. Anderson  PE

----- Original Message -----
From: "James F Fulton" <James_F_Fulton(--nospam--at)RohmHaas.Com>
To: <seaint(--nospam--at)seaint.org>
Sent: Friday, September 15, 2000 7:14 AM
Subject: Truck Axle Loads


> >From my references, for H20-S16-44 (now called HS20-44 ?) truck, the
maximum
> axle load is 32 K on a single axle or 16 K on *each* of two axles in
tandem.
> A few questions please: (1) For trucks with triple axles in tandem (like
> tanker trucks or heavy dump trucks I've seen), is the maxium load still
> limited to 32 k on the combined axles ?
No, the reality is that if not regulated by DOT enforcement, there are no
"limits", except those self-imposed by the trucker/operator.  Triple axle
group capacities on highway equipment can range to 70,000+ lbs if not
otherwise regulated.  In the "old days", when the width of tires was
measured in inches, an adequate rule of thumb for tire load capacities was
about 600 lbs per inch of nominal tire width.  Thus about 6000 lbs for a
tire of 10 inch nominal width, or 24,000 lbs per standard drive or trailer
axle.  For the "standard" 18-wheeler, this summed to about 108,000 lbs,
which is beyond most DOT limits, but nonetheless within the capacity of the
equipment.
(2) In reality, do single axles
> carrying 32 K exist, or are they always at least two tandem axles to carry
> this large a load load ?
Yes, particularly on un-regulated short-hauls.  It depends on whether or not
the trucker is regulated.
(3) Is the situation different any in Canada or
> Europe from the US ?
I would assume that the laws of the trucking industry are about as immutable
as the laws of physics.

I am really trying to determine if the design assumption
> of 32 K on a pair of tandem axles covers is the real worst case for
> structural slab design at a tanker truck load/unload station .  Thanks in
> advance for any feedback.
>
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