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RE: Simplified Seismic Design Trends

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Thanks for chiming in Scott.

Caution is always good and your points are well taken. However...and there's
always an however... my impetus was/is to justify increased design time
(number crunching) against increased product safety.

In my mind simplification means getting the right feel for level of forces,
weak points, needs for critical connections, etc. in a smaller amount of
time such that the work of creative problem solving and detailing can take
the larger portion of our time. I would agree that just "bumping up the
numbers" can be construed as simplifying the design however that's not what
I would ask for us to look at. I guess my beef is when I spend significant
design time and the "numbers" are not all that different from the way I did
things under a previous code, then I question the change.

Construction costs will always be a consideration (isn't that one reason we
strive to refine the system needs?) and I would argue that more design time
needs to be devoted to this consideration. Both points, simple design
requirements produce higher construction costs and more design time helps
pare construction costs, are valid in my mind. The final result is a
balance, and since lateral design loads are significantly less accurately
known than gravity forces I'd easily recommend more caution with the higher
unknown. 

So my parting thought is this. Let's be advocates for better understanding
of lateral designs for buildings (EQ and Wind) but not fool ourselves into
thinking we can always do it less expensive than before. If we want to be
believed (respected) then we have to behave like a profession willing to
take a hard look at what we promote.

Barry H. Welliver
barrywelliver2(--nospam--at)earthlink.net
 

-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu] 
Sent: Monday, May 12, 2003 5:31 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Simplified Seismic Design Trends

I would argue a little caution.  In general, "simplified" design
procedures tend to mean that more generalized engineering assumptions need
to be made which tends tends to result in more conservative designs (good
from an engineering point of view).  While this is potentially good from
an engineering point of view from both cost/time and potentially safety
(assuming some of those "generalized engineering assumptions" don't
include anything that would result in unsafe assumptions), it typically
means that construction costs will be higher as typically more
"conservative" designs tend to result in things like more material and
other construction related costs.  And like it or not, constructions costs
tend to be MUCH more significant than design costs...from the point of
view of the client who is paying both costs.

Thus, the question becomes one of can you justify the cost to your client
to build the project WHILE also justifying the your cost to produce the
design.  You might save TONS of time with a more simplified design but end
up producing designs that cost significantly more to construct.  Thus,
while you might be able to lower cost of design services to the client
(or just increase your profit without lower the client's cost), clients
may ultimately pass you by to go with someone who charges them a little
more (or the same amount) to get a design that costs significantly less to
build.

The point is that simplified design, while nice and desirable for many
reasons (less engineering time involved, less likely for
misinterpretations/mistakes to be made, etc), also has some downsides
that you need to be aware of.

HTH,

Scott
Ypsilanti, MI


On Mon, 12 May 2003, Jim Persing wrote:

> Barry, I totally agree with you.  And ditto for wind.  The more simplified
> provisions should be the code and what we have now should be in an
appendix
> for use by those who can justify the expense for their larger projects.
>
> We should be spending more time designing structures and less time
> calculating loads.
>
> Jim Persing, PE
>   -----Original Message-----
>   From: Barry H. Welliver [mailto:barrywelliver2(--nospam--at)earthlink.net]
>   Sent: Saturday, May 10, 2003 6:28 AM
>   To: Seaint Listserv
>   Subject: Simplified Seismic Design Trends
>
>
>   I'm looking for some help in identifying any movements or trends to
> support a simplification in seismic design. I recognize that we have
efforts
> to that effect in the building code (and they are greatly appreciated by
> small budgeted projects) and am interested in both participating and
> encouraging these endeavors.
>
>
>
>   While one mans simple is another's complex, it does seem to me that the
> trend in code making is a both/and mentality. It's wonderful that we have
> both researchers and practitioners hammering out rules, but I fear we've
> lost the ability to distill what we know and focus on getting the most for
> our design dollars. Perhaps I've developed this sinking feeling based on
> comparisons between my practice 20+ years ago and today. I've been (and
> continue to be) an ardent supporter of EQ code evolution and think for the
> most part the directions have been justified. I get frustrated however by
> the quickly adopted provisions which get universally applied to general
> building design and then get massaged with additional formulation and
> exceptions. (EOR = End of Rant)
>
>
>
>   Of late I've been coming back to the thought... if Einstein can boil
> science down to E=mc2, then surely mere structural engineers can aim
toward
> M=wl2/8.
>
>
>
>   Your comments and suggestions would be appreciated.
>
>
>
>   Barry H. Welliver
>
>
>
>


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