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Re: Concrete vs. Steel

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     I'm not saying that R/C won't work.  I'm saying that the better choice
(IMO) is steel.  Supporting arguments:

1.  To a point as with any material, concrete works fine in bending.  But,
in cyclic shear + tension it fractures one side at a time until all that is
left is two cone shaped ends with rebar holding them together and no
frictional surface.  Steel is ductile and concrete is brittle.
2.  The bay bridge failed in shear (I SAW the joints) at d/2 to d below the
knee.
3.  You can't fix wrongly detailed concrete.
4.  In the event of collapse, with concrete people get buried and steel
maintains a space (better)(~).
5.  With n=9(+) and weight per unit vol. =3.3 for steel/concrete the
strength to weight ratio makes steel a better material where mass is a
critical factor.

So much for that ACI Fellowship,
(no offense to ACI)
Greg


-----Original Message-----
From: Mark T. Swingle <mswingle(--nospam--at)earthlink.net>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Monday, October 25, 1999 3:19 AM
Subject: Re: Concrete vs. Steel


>Dear Greg in OK,
>
>Please don't come to California to design until
>you do some more
>homework! :-)
>
>Well-designed and -constructed concrete is a very
>viable and ec-
>onomical solution in all areas of high
>seismicity.  This type of
>structure has been proven safe in many
>earthquakes.
>
>The problems in Turkey were apparently due almost
>entirely to two
>factors: 1) poor detailing, and 2) poor material
>quality.
>
>In Kobe, steel buildings were affected as much, if
>not more, than
>concrete buildings.
>
>If you drive over the Bay Bridge, the only
>"obvious" thing is that
>it is made of steel, not concrete.  It was steel
>connections
>that failed.
>
>By your reasoning, perhaps we should prohibit the
>use of steel
>connections (in buildings as well as bridges) in
>earthquake country,
>based on the experience with the Bay Bridge and
>Northridge.
>
>Mark Swingle, SE
>Oakland, CA
>
>
>Greg Smith wrote:
>
>>  To be in charge of a project and prescribe the wrong material
>> (even for economical reasons) is like a doctor prescribing the
>> wrong medicine because the patient can't afford the right one.
>> In engineering as with medicine, this can lead to death.
>
>> I believe that concrete has been WRONGLY prescribed ANYWHERE in a
>> high seismic risk zone.  The EQ's in Turkey, Bay Bridge, Japan etc.
>> are obvious proof of this.  Yes, it is possible to construct a
>> concrete structure that will withstand a Richter 10 but THAT would
>> be UNeconomical.  Granted that Northridge revealed problems with
>> steel and brittle fracture, it will be easier to overcome this
>> than to take the mass out of concrete.  Concrete has it's
>> advantages but only in a compatible location.
>>
>> Greg in Oklahoma
>