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RE: News from the IBC front

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I sent this posting yesterday, but I got a note back that it was too long
for the list server. I am not sure if any one got it. I am sending it again
(without the complete thread) in case it didn't get posted. If you have seen
it, my apologies.

Mike

Two points of clarification in regard to your comments:

1-	The proposal for applying the 10/l limitation to all types of
construction was rejected mostly because of an opposition from the concrete
industry representatives. Dr. Ghosh (eloquent as usual) spoke against the
application to all types of shear walls because it might encourage short
shear walls, which are more problematic in concrete and masonry
construction.

2-	The exception for Rho coefficient application to diaphragms (which I
wholeheartedly agree with) was defeated mainly due to the opposition from
the FEMA/NEHRP people. I think that group is probably the only one that sees
justification in applying a factor, which is entirely based on the vertical
lateral force resisting system, to a horizontal element which rarely has
been a problem. Unfortunately, the opinion of this single group carries an
unproportional weight for most of the committee members. 

Ben Yousefi, SE
San Jose, CA




 

	-----Original Message-----
	From:	Mike Valley [SMTP:mtv(--nospam--at)skilling.com]
	Sent:	Monday, April 24, 2000 12:30 PM
	To:	seaint(--nospam--at)seaint.org
	Cc:	Bill(--nospam--at)AllenDesigns.com
	Subject:	RE: News from the IBC front

	Bill:

	I think you did have it figured out.  It appears that the code
	bureaucracy has screwed up the redundancy factor beyond belief.  In
	addition to your conversation with Dick Phillips, consider the email
	message from Ron Hamburger to this list.  (I've inserted it after my
	comments.)

	Although Ron notes that the 10/lw factor "has some serious negative
	impacts on wood frame construction", that observation follows a long
	discussion of the fact that the original code writers NEVER intended
	that 10/lw be taken greater than 1 FOR ANY TYPE OF CONSTRUCTION.
The
	SEAOC proposal to change the IBC erroneously applied only to
	"light-frame construction".  SEAW attempted to fix the SEAOC
proposal
	on the floor at the code hearings.  The proposed modification was
not
	accepted; as a result, the 10/lw problem was only fixed for
	light-frame construction.  Evidently SEAOC can't (collectively)
figure
	out and agree upon what 10/lw means.  Because of that, it hasn't
	really been fixed.

	A related problem was also NOT fixed at the IBC hearings.  There was
a
	need to clarify that the redundancy factor (which is related to the
	performance of the entire system) should not apply to prescriptive
	forces that are not related to the performance of the entire system.
	The most obvious example is the prescriptive diaphragm forces.  As
	discussed in the "Blue Book", the redundancy factor should only
apply
	to the diaphragm forces that are related to transfers of forces at
	offsets in the vertical elements of the lateral-force-resisting
	system.  In other words, diaphragms should only be penalized for
lack
	of system redundancy when they are part of the global load path (and
	not when they are simply delivering local loads that are unrelated
to
	system-wide redundancy).  The SEAOC proposal to fix this problem was
	rejected.

	In my opinion, both of these issues reflect a growing problem.  Many
	of those involved in today's code writing and adoption process have
	either forgotten or never known the reasons behind the code
	provisions.  Rather than read code commentaries (the Blue Book,
NEHRP
	Commentary, and others) or ask those who were involved, they close
	their eyes and dream up (flawed) rationale for the current code
	provisions.  More often than not, that rationale reflects their
	personal/professional bias rather than the original intent or real
	data and the code becomes a confusing political (not engineering)
	document.

	-Mike

	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-
	Michael Valley, P.E., S.E.                   E-mail:
mtv(--nospam--at)skilling.com
	Skilling Ward Magnusson Barkshire Inc.
Tel:(206)292-1200
	1301 Fifth Ave, #3200,  Seattle  WA 98101-2699      Fax:
-1201