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Re: Effects of the New Code on Wood structures - good or bad?????-Part 1

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"Swingle, Mark" wrote:
> I would like you (or anyone else) to explain
> exactly what has changed in the 97 code that leads to your ranting and
> raving.  I am unable to find the major changes of which you speak.  You keep
> blaming the new code and speak with urgency about it due to the fact that it
> took effect in CA this July 1.  The relevant portions of which you complain
> the most have not changed at all since the 1994 UBC, and have not changed
> significantly since 1967.
> 
This is a good questions, and I would also like a response to this. 
However, my feelings are that if there are in fact no changes in the
Code, and we as an engineering community have been successfully ignoring
these sections of the code for 30 years, then WHY CANT WE CONTINUE TO
IGNORE THIS STUFF!!!

> What is happening is that the professional community is only now catching up
> to what has been in the code for over 30 years.  The design examples you
> cite are just the first step in that catch-up process, but it is not a
> result of any new code provision.  As I understand it, these new examples
> simply perform both a rigid diaphragm and flexible diaphragm analysis, and
> simply use the worst case for each, so no consideration of diaphragm
> stiffness is required.  For the flexible case this is simple, and is the way
> it has been done typically in the past.

This is not exactly true.  Many plan check agencies are not always up on
the latest code developments.  An exception to this are DSA and OSHPD. 
The plan checkers for these agencies are very experienced structural
engineers.  We recently had a fairly good size DSA project we did. 
Prior to our starting on the project, I met with the DSA and told them I
was considering designing the diaphragms as rigid, because that is what
the Code clearly said.  With full knowledge of what the code said, the
DSA plan checker said that if I wanted to do a rigid analysis on the
diaphragm, that was okay, but that I would have to also do a flexible
diaphragm analysis and the building would have to fully comply with the
results of that analysis.  They basically were not going to require the
rigid diaphragm analysis, and in fact WOULD NOT ACCEPT that type of
analysis alone.
I find it very interesting that DSA would not accept the Code required
analysis.  They want it done based on flexible diaphragm, and will not
accept a design that does not include this, even though it is clearly
not required in the Code.

These people are aware of the Code requirements, and do not accept it. 
It is not because the are ignorant of the Code.


Lynn