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Re: Effects of the New Code on Wood structures - good or bad?????

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: Re: Effects of the New Code on Wood structures - good or bad?????
• From: "Swingle, Mark" <Mark.Swingle(--nospam--at)dgs.ca.gov>
• Date: Fri, 23 Jul 1999 17:39:42 -0700

```Dennis
Determining the deflection of a simple span diaphragm - blocked or
unblocked, is not sufficient to determine how it will redistribute
horizontal shears if you have determined that it will act more rigidly than
purely flexible.  Please read again what I wrote.

Charles
I never once said that my method of bracketing the shears was an absolute
code requirement, I was simply proposing it as a way to cover all bases.
Everyone is complaining about the complexity and litigation, and going on
and on about diaphragm analyses etc., so I proposed a method where you could
be 100% sure that you would not underdesign any wall according to the code,
without doing anything with the diaphragm.  So now you are complaining that
I have simplified something that others were saying was so complicated.

It goes without saying that engineering judgement still has a part, but I
guess now I have to say it.  Engineering judgement still has a part in this.

Obviously, after one has "considered" the worst cases, a judgement is made
as to what is a reasonable force for each wall, and you go to sleep
peacefully.  If you find out that the difference in shears between the two
methods is only 10%, then you can easily bump it up if you want, or leave it
alone.

I maintain that this is a more rational method of design than using Rw=6, as
others have proposed.  If you find that the difference is 50%, then you have
found out some valuable information about your configuration and, again,
make some judgement as to what you are going to do about it.  An experienced
engineer can look at the building on paper and determine whether there is
going to be a variation of 10% or 50% without doing any calculations at all.

Saying that the word "considered" only requires thinking about it and not
acting upon it borders on the ridiculous.  The considering is a mathematical
considering, not a fantasy.  We consider live loads and dead loads all the
time, and then we act upon it.

Please reread what I wrote and put it into the context of what we're talking