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From: Jim Wilson <wilsonengineers(--nospam--at)yahoo.com>
Subject: Re: Bridge/building
To: seaint(--nospam--at)seaint.org

Ken,

How does the cost of a bridge designed for full
vehicular loadings + the cost of the buildings work
out?  The differential cost for the buildings not
having foundations could compensate for some
aggravation factor.

Jim Wilson
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--- Ken Peoples <kspeoples(--nospam--at)lvta.net> wrote:

> We have a client who would like some rough ball park
> cost figures for a bridge/structure over a river. 
> The bridge is not for vehicles, but for pedestrian
> traffic and shops/restaurant.  
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From: "sscholl2(--nospam--at)juno.com" <sscholl2(--nospam--at)juno.com>
To: seaint(--nospam--at)seaint.org
Subject: Re: Bridge/building


"light truck traffic" to a restaurant is not light.

The Coke delivery trucks are about as heavy as they come- perhaps
lighter than a ready-mix truck but not much. One broke through the Santa
Monica Pier about 15 yrs. ago.

Stan Scholl, P.E.
Laguna Beach, CA

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OK, my turn.  I think everyone is missing some major points here.  First
of all, trucks are still lighter than pedestrian loading.  Even Coke
trucks.  Their concentrated wheel loads are huge, but on a square foot
basis they're not as heavy as a lot of people standing close together.

Next, buildings are designed with a floor live load, plus there's the
weight of the building itself.  If some of the buildings qualify as
"places of public assembbly," the live load alone is the same as a
pedestrian live load.  So buildings are probably heavier than either
trucks or people.

And you don't save the cost of the foundations.  You still have
foundations.  They're just 250 feet north of where the load is.

Ken, if I was drinking with someone and they asked me that question, I
would guess anywhere from 500 dollars a square foot on up, just for the
bridge.  At 2000 feet x 100 feet, that's 100 million dollars at best.
Pricey real estate.  There is a bridge over I-90 west of Chicago with a
McDonalds rest stop on it; there's a US Post Office somewhere (New York,
I think) built over railroad tracks with 10 foot deep plate girders.
Maybe you can track them down.

Finally, I have to tell you--you seem to look at a lot of projects
which, judging by the questions you ask, you are only barely qualified
to do at best.  What is your criteria for rejecting a project?  A bridge
with spans of 500 feet is something a lot of very well qualified bridge
engineers would think twice about taking on.  You're way outside of the
range of beams.  A bridge like that wants huge trusses, arches, or (God
help you) some kind of cable suspension system.  You can't even begin to
think about something like this without detailed geotechnical
information; bad soils could easily double the cost of such a project.

My advice, and I don't intend this to be belittling because I do a lot
of them, is to go find a nice mezzanine to design.

Michael Hemstad, P.E.  
Saint Paul, Minnesota 

 

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