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Re: Concrete vs. Steel

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>      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.

I certainly can't agree with those anti-concrete statements.  Well designed
concrete is entirely appropriate for high seismic regions, perhaps even
preferable.  Having seen some of the information brought back from Turkey, I can
only say that much of the construction and design quality was was so
unbelievably poor compared to what a U.S. code would require, that it is barely
even worth discussing.  It certainly does not constitute "obvious proof".  Many
of the buildings in Turkey that used things like ties in the columns and
deformed bars performed just fine (in steel design terms, advising these
rudimentary steps would be like saying try to stay away from cast-iron).  The
double-deck freeway that collapsed near Oakland is also in this category.  The
connection detailing was very poor by current standards, and so is no benchmark
of modern concrete construction.  Using these to condemn concrete is like saying
that Northridge was "obvious proof" that steel buildings are not appropriate for
high seismic regions.  In either case, good design, utilizing the latest
technology and materials, and being incredibly careful with detailing, makes all
the difference.  Be careful about using Japan (I am assuming you mean Kobe
specifically) as an example, since many of the building failures there were in
steel construction.  You could easily undermine your own point.

Here in Seattle (Zone 3), it seems that 75% of the large buildings currently
under construction (my guess based on living here and driving around) are c.i.p.
concrete.  Concrete may have higher mass, but it has a very favorable
damping/energy dissipation when properly confined and detailed.  It also tends
to have longer periods of response due to its higher mass.  When properly
confined and detailed, concrete is an excellent choice for resisting seismic
loads.

Paul Crocker