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FW: dynamic lateral force procedure

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BRAVO! BRAVO! BRAVO!

Well said Eric!

I have compared using a commercial computer program to hiring a person 
without knowing the person's name, education, experience or background; 
sitting him/her down at a drafting table to do calculations,  getting the 
"answers" back without supporting calculations and being assured that the 
answers are correct, and if they aren't correct, it's your responsibility.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Eric Gillham wrote:

. > OK, I'll weigh in with an IMO:

. > The attitude that more complex dynamic analyses utilizing faster and 
. > better computers is the inescapable wave of the future for our profession 
. > is IMO misguided and shortsighted.

. > Misguided because in the end it places more faith in a computer, and a
. > program written by someone else whom the designer probably hasn't met and
. > who they are basically relying upon to produce a safe and economical 
. > design. FEM programs are too the point where even if the programmer 
. > provided the code, it would be impractical to even attempt to check it 
. > --> the "black box" scenario.

. > Shortsighted because it lends momentum to a cycle of having to use a
. > computer driven dynamic analysis because the building is too complex to do
. > using a static procedure, after which the architect says "well, they 
. > handled that one, so the next one can be even MORE complex", and so on 
. > and so on. And no, I don't think that architects are evil, just that they 
. > will push to satisfy their needs, just like everyone else, unless an 
. > opposing force resists them.

. > I strive to work with my clients to REDUCE the complexity of the 
. > STRUCTURAL system so that I am not forced to use a dynamic analysis. In 
. > my experience it is quite possible to create a simple, symetrical 
. > structural system that is rational and can be understood, then hide it 
. > with architectural elements that create the effect the architect desires -
. > everyone is happy.

. > The problem that I see with the trend towards "throw more computer power 
. > at it" is that the designer soon gets to the point where checking the 
. > design, and fully understanding it, is next to impossible. Sure, one can 
. > still to a base shear check for equilibrium, but the mechanism formation 
. > for the biggie earthquake is a toss-up.

. > Besides, even today most analysis programs are still ELASTIC, and as we 
. > all know, most of our designs are done with INELASTIC mechanisms in mind. 
. > There are inelastic analysis programs out there and I have used them 
. > (mainly for checking older, existing structures), but the application WRT 
. > a new design is limited, IMO, unless it is for a final check.

. > On the other hand, maybe it's because I enjoy being able to put down on
. > paper, with a reasonable degree of certainty, just how the mechanisms are
. > likely to form. If that is the case, then it is probably just hubris on my
. > part - but I'll continue to do it :)

. > My to cents.


. > T. Eric R. Gillham PE

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