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RE: Truck Design Loads

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-----Original Message-----
From: Jason W. Kilgore [mailto:jkilgore(--nospam--at)] 
Sent: Tuesday, July 13, 2004 4:49 PM
To: seaint(--nospam--at)
Subject: RE: Truck Design Loads

> Missouri allows heavier trucks in the two major urban areas (Kansas City
> and St. Louis).  Bridges in these areas must be designed for the
> "Missouri-Modified" AASHTO loads.  Off the top of my head, I believe it's
> about 20% higher than standard AASHTO.

Sounds like the old "HS-25" loading that someone came up with a few years
back to account for "heavier trucks." It was simply HS-20 x 25%.

Frankly, we determined some time back that the "new" HL-93 loading (which I
think may since have been modified) from the more recent AASHTO LRFD Bridge
Design Code was far more realistic--and slightly conservative--in comparison
with "HL-25." Also, easier to implement because you don't have all these
permutations as compared to the old AASHTO "Standard Specification".

And before the typical flame-war erupts again, HL-93 is not LRFD-specific;
it's just that the AASHTO folks took the occasion of development of the new
LRFD standard to revamp everything, including adopting a more rational, "ACI
318-like" layout.

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