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Re: Structural Drawings with PDMS ?

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Raul,

        It sounds great!  I'm sure they also point out that you can completely
optimize the structural and keep up to all design changes as they
materialize!!  But this is utopian and can not be achieved in reality.

        The best the program can do in reality is perform a code check on
predetermined sizes; it can not optimize sizes for several practical reasons,
mostly financial.

        Because these projects (I'm referring to industrial projects such as
refineries and the like) take a long time to design, interest charges are
accruing on the construction financing, and the product is usually pre sold
(including the delivery schedule), there is intense pressure to have the civil
and structural work done (actually constructed in the field, not just designed)
long before all of the equipment loading is accurately known.  This makes it
quite common to "take your best guess and add 30% to all loading (they later
reinforce those components found to be under designed during the later
reviews), particularly when the structural cost is a small fraction of the
total cost.

        For a real life example, I once worked on a gasoline refinery which
required piles (with driving tips and using the heaviest section in the
Canadian steel handbook) 110 feet long.  At the time these cost about $5 000,00
each; and when I tried to get better information in order to save a few piles I
was informed "Daryl, we have $90,000,000.00 worth of piping materials in Area
20 alone!  We don't care if you do waste a few piles."  This same project had a
$500,000.00 per day penalty clause for late completion; they really didn't care
if we wasted a few piles or if the structural was 30% over designed!

        That's only for design.  Once the project is completed the operating
people begin looking for ways to change and improve and fine tune the
operation.  This includes things like adding monorails and jib cranes in
addition to modifications to the piping and to the process itself.  Having the
structural completely optimized (read that maxed out) would be counter
productive.

        Just some thoughts.  Hope they're not too far off topic.

Regards,

H. Daryl Richardson

Rlabbe wrote:

> List,
>
> I would like opinions on this issue. Regarding large industrial engineering
> jobs where all disciplines are involved, piping, mechanical, HV&C,
> structures, etc. it is coming a usual procedure to handle all of the design
> activities through PDS or PDMS modeling tools. It seems to me, that these
> fancy models have been conceived for piping / mechanical lay-out issues.
> How benefitial is this way of design, from a structural standpoint ? The
> vendors are usually mentioning steelwork design, as one of the resources
> availabe. The main and critical structural issues, like special seismic
> connections,
> or details, are they well covered ? The out-put, is it proper to check all
> these
> issues ?, etc.etc. Anything about the reinforced concrete structures, in
> this
> environement ?
> Any experience, or case study, or opinion about, would be appreciated.
>
> Regards,
>
> Raúl Labbé S.E.
> M.ASCE.
>
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