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Re: SAP SHELL DESIGN

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Chris' response was appropriate based on the way you phrased the question.

There is nothing more dangerous, in my opinion, than an engineer who blindly trusts software to do their job. Fine if you gain trust and can verify the results in the software, but that's something that happens over time. It sounded very much like you were basically saying "hey, tell me how to do this in SAP because I've never done it before and need to get this thing off to the client"

Chris has always been adamant against and cautious on this list about people using FEA software who don't know EXACTLY what they're doing. I think what he writes, although probably difficult, upsetting, and harsh to read as the person who posted the question, is correct.

But don't take it personal. :-)

-g

On 5/21/07, hossein mardanlo <hosein.mardanloo(--nospam--at)gmail.com > wrote:
ok, I got the point. You are not familiar with SAP. If you were, probably
you must had known that CSI company, producaer of SAP2000 has been adding
some new features to include concrete shell design based on specific design
Codes. I wanted to know if anyone had more information about it. It is of
very much surprise for me that you beleive softwares can not DESIGN
structural elements. Many of list members know that ETABS and SAP and many
other softwares do design for beams, columns, and ETABS does for walls. Of
course every engineer must check the results, but we can't say software
never design.

Hossein Mardanlu
----- Original Message -----
From: "Christopher Wright" < chrisw(--nospam--at)skypoint.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Sunday, May 20, 2007 12:49 PM
Subject: Re: SAP SHELL DESIGN


>
> On May 20, 2007, at 10:44 AM, hossein mardanlo wrote:
>
>> It seems you have got a lot of negative energy from someone recently!
> It sure does, doesn't it?
>
>> Anyway, I have been using applied mechanics for many years  successfully,
>> maybe more than you!
> It's possible--I wouldn't bet on it.
>
>> And of course I always will need to learn more, even though  someones
>> like you may doesn't need for more learning!  But using  new methods are
>> always necessary. I wish You could answer my question!
> Your question really had no answer, since you didn't specify what  kinds
> of suggestions you were after. SAP2000 does what it does--
> nothing to suggest. SAP 2000 is like ANSYS or NASTRAN or other  general
> purpose FEA software--they do analysis, not design. Design is  an
> engineer's job. Sometimes you'll find program features that seem  to mimic
> design, but they're usually doing iterative analysis based  on
> user-specified criteria. Codes like the AISC Code or the Boiler  Code rely
> almost exclusively on manual calculation and proportions  for details
> which have given satisfactory service.
>
> That said there's not a whole lot of structural code provisions
> specifically addressing general shell theory. I don't use SAP2000,  but
> from what I read the Code provisions it incorporates are aimed at  framed
> structures. The design methodology in the ASME Codes is based  on shell
> theory, and there are areas in those Codes that are written  around the
> use of FEA output, but the loading and service doesn't  apply for all
> fields of engineering. It's not too tough to apply  equivalent standards
> to shell element results for metals, once you  know enough mechanics to
> understand the basis of Code provisions.  ANSYS, for example, has no AISC
> Code post processor, but it's fairly  simple to do the arithmetic with a
> spreadsheet using tabular output  if you're dealing with plate structures
> or shells.  If there are  programs which do anything other than simple Div
> 1 design (like  Caesar or Codeware) I'm not aware of them. ANSYS will
> provide  primary, secondary and peak stresses, for Nuclear Code
> assessment,  but it's really doing an analysis task, not design, and it
> should  only be used by engineers who really know their stuff, because
> it's  easy to confuse things.
>
> You didn't mention whether your plant design problem involved metal  or
> concrete. I daresay the ACI has provisions for shell like cooling  towers
> or domes. There may even be software which does design tasks  like re-bar
> placement but I don't do concrete, and I don't keep up  with it. The ASME
> Nuclear Code also covers concrete containment  vessels, but again, I don't
> know of software that actually designs  these things. Again--it's the
> engineer who does the design, using FEA  results.
>
> Christopher Wright P.E. |"They couldn't hit an elephant at
> chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
> .......................................| John Sedgwick, Spotsylvania
> 1864)
> http://www.skypoint.com/~chrisw/
>
>
>
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--
-gm