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RE: '97 UBC Lateral Design - Envelope Solutions???? - Part 1

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Hey, Dennis.

Good panel on Saturday. (Sorry I rushed off but I needed to hitch up the
trailer and vamoose to San Diego.) Good as far as it went which,
unfortunately, wasn't very far.

John Coil mentioned an SEAOC Proceedings paper from the late 70's that I
actually read and heeded. I did my first envelope design on a three story
wood frame hotel about 15 years ago. Of course the concept made much sense
since the floors had concrete topping (hard rock, not cellular), were fully
blocked  and had small aspect ratios. And I have never done such an analysis
on a residence other than to make ad hoc adjustments where appropriate due
to unusual conditions. I usually design the rear wall of the garage for the
full garage shear whether seismic or wind.

I disagree, however, with the option of eliminating conventional framing
provisions as such. I agree that they are inadequate and should be
strengthened. But, as you noted, we simply cannot force the cost of housing
out of the reach of low income individuals.

The standard way we deal with force is one of the difficulties. As engineers
we tend to increase strength when faced with increased forces. As many of us
discover the resulting increase in stiffness has a way of making the
situation worse rather better. I believe that the way to solve the problem
is to use lightweight materials more effectively. The use of such materials
will be limited until the development costs have been amortized. Ultimately,
though, I don't see that there is much choice for housing.

Mark Deardorff

-----Original Message-----
From: Seaintonln(--nospam--at) [mailto:Seaintonln(--nospam--at)]
Sent: Sunday, October 03, 1999 4:27 PM
To: Mark.Swingle(--nospam--at)
Cc: seaint(--nospam--at)
Subject: Re: '97 UBC Lateral Design - Envelope Solutions???? - Part 1

The most rational comments to come out of this panel discussion (see my
specific post) is the agreement that the development of load paths and the
proper detailing and implimentation is much more important than the design
methodology used.

I was not trying to become a proponent of rigid analysis - it has it's
but not in custom residential homes in my opinion. My point was that on
certain types of structures there was too much discrepency between methods.
This was not pointed out by the panel members who looked at fairly regular,
rectangular structures as models. I think a good case in point was John
model of the retrofit of the four story apartment buildings where he placed
the entire lateral restraint system in the center of the buildings -
essentially creating a core with two cantilevered, open front sides. I don't
believe this is appropriate in wood structures regardless of how stiff the
core is - but only time will tell.

I'm not sure we would be in this debate had engineers designed narrow but
highly loaded plywood paneled walls for deflection rather than simply code
allowable aspect limits (H/b).
These thoughts were supported by the comments made by Andrew Adelman(?) -
City of Los Angeles and Chris Christokas (DSA).

As far as being true to my word - the difference in politics and science is
our ability to change our position on the evidence of truth. We are still
from proving the benifits of the code methods for wood structures or
justifying a change in methodology which is not attributed to loss of life
high degrees of structural damage.
Regardless of what I think, aren't these the most important issues?