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Re: LRFD and AASHTO

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The 4th Edition (2001) is now available.  I think it is still ASD (based
upon comments in the preface), but now also includes fatigue issues.

M. David Finley, P.E.
Lake City, FL  32025

----- Original Message -----
From: "Bill Polhemus" <bill(--nospam--at)polhemus.cc>
To: <seaint(--nospam--at)seaint.org>; <EllisAL(--nospam--at)c-b.com>
Sent: Thursday, October 25, 2001 10:27 PM
Subject: RE: LRFD and AASHTO


> Amy, for design of sign supports using AASHTO's "Standard Specification
for
> Structural Supports for Highway Sings, Luminaires and Traffic Signals"
1994
> Edition, you must use ASD, period. There is really no "cross-over"
> permitted.
>
> Now, that's not to say that LRFD design couldn't work; from what I've been
> able to determine for myself, the design equations, etc., for steel design
> in the AASHTO Standard are pretty much equivalent to those in AISC ASD
Ninth
> Edition spec. But I am willing to wager that your design calcs, etc., are
> going to have to be "checked" by TxDOT--at least that's been my experience
> designing such supports for Houston METRO--and TxDOT is not even willing
to
> look at LRFD stuff.
>
> One particular problem with design of sign supports, etc., using this
AASHTO
> Specification, is that they are trying to "bridge the gap," pun intended,
> between the world of AISC design and AASHTO's own bridge design
> specifications. The design equations, etc., as I've said, boil down to
AISC
> ASD, but the "flavor" of the spec, the way loads are treated, the standard
> units used, etc., are very familiar to the bridge designer who uses
AASHTO's
> ASD bridge spec. It looks to me like AASHTO is stricken with the "Not
> Invented Here" syndrome.
>
> Now, I have just ordered the 2001 edition of the AASHTO "Signs"
> specification, but I haven't yet received it. It could be that they have
> updated it to conform to LRFD, since that is the way the AASHTO has been
> pushing to go for some time, at least for bridge design (their First
Edition
> LRFD Bridge Design spec was published in '94). If you can get a copy of
that
> (can be ordered here:
>
https://www.aashto.org/publications/bookstore.nsf/Thankyou?openform&id=LTS-4
> ) then that might be your best bet.
>
> Otherwise, I'd be glad to let you know how things stand when I get mine.
>
> Regards.
>
> -----Original Message-----
> From: Amy Ellis [mailto:EllisAL(--nospam--at)c-b.com]
> Sent: Thursday, October 25, 2001 10:10 AM
> To: seaint(--nospam--at)seaint.org
> Subject: LRFD and AASHTO
>
>
> I am a recent graduate and would typically use LRFD in designing.  My boss
> typically uses ASD.  I am just doing simple sign structures for DFW
Airport
> but the question has come up, how does LRFD fit in with AASHTO?
> Specifically we are looking at the different load combinations and which
> factors to apply.  If anybody has any ideas please respond directly to me.
>
>
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