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Re: Sign Structures

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No problem with that.  On a 25' tall billboard, I believe a dynamic analysis is a wee bit excessive...

On Fri, Feb 29, 2008 at 2:51 PM, Harold Sprague <spraguehope(--nospam--at)> wrote:
The sign in question does not warrent a dynamic analysis, but there are signs along the strip in Las Vegas that sometimes are evaluated in wind tunnels with modifications at the base to determine a dynamic response. 
The Hilton sign in Las Vegas is 279' tall with a terrible plan and elevation aspect ratio.  The sign it replaced blew down in a wind storm. 

Harold Sprague

Date: Fri, 29 Feb 2008 09:15:41 -0800
From: d.topete73(--nospam--at)
To: seaint(--nospam--at)
Subject: Re: Sign Structures

A "dynamic" analysis for a billboard....  Tomfoolery at its highest...

On Fri, Feb 29, 2008 at 5:00 AM, Gary L. Hodgson and Assoc. <ghodgson(--nospam--at)> wrote:
Thanks, Harold
I will be doing that.  There is no guidance in our codes on signs or
other non-building structures. Your codes go further than ours, as ours
are only written in regard to buildings.  If I want to design a crane
runway, storage bin, or sign _for seismic loads_, I have to refer to
American publications. The problem is that our codes don't use the same
terms or geographical data.
In going up against this municipality, I have to be on firm footing,
because my customer has a history of bad relations with them--he has won
two law suits against the city and their three page letter (of
structural questions only) came two days after the latest judgement was
published in the newspaper.  This city has the first or second highest
average income in Canada and they don't like billboard signs, even if
though there a lot of them existing in the city.  One of the questions
was "did I do a dynamic analysis of the structure" (for a 20'x10' sign
with a top at 25' above grade).
How many cases of beer do I owe you now?

Harold Sprague wrote:
> Gary,
> The projected area in the plane of the sign is relatively small.
> Seismic may govern.  You could categorize signs as nonbuilding
> structures.  The loading is a function of the force resisting system
> which establishes the response coefficient and the mass.
> Regards,
> Harold Sprague
> > Date: Thu, 28 Feb 2008 17:04:42 -0500
> > From: ghodgson(--nospam--at)
> > To: seaint(--nospam--at)
> > Subject: Sign Structures
> >
> > List,
> > I design sign structures for 2 clients-these are all free-standing
> signs
> > on one or two posts. In our area, generally wind governs. A
> > municipality has questioned whether I designed a particular sign for
> > seismic loading. Nothing in our codes addresses the issue of signs
> > subject to seismic loading unless they are part of a building, in which
> > case they are considered a fixture just like a mechanical piece of
> > equipment. Our codes only require that signs over a certain height or
> > area have to be designed by a professional engineer. So, I guess my
> > question is what seismic loading do you design signs for? Thanks in
> > advance.
> > Gary

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