Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Wood: Conventional Framing opinions needed from otherstates -Reply

[Subject Prev][Subject Next][Thread Prev][Thread Next]
In a message dated 97-12-01 13:19:47 EST, Tim McCormick write:

> 1. Conventional framing provisions require less story strength than the
>  minimums allowed for engineered designs.

No argument there.  But for houses, and that's about the only type of
occupancy that conventional framing provisions are used on, the records on
injuries and deaths don't demonstrate that greater story strength would have
any benefits. 

>  2. Deaths and personal injury HAVE occurred in buildings which met or
>  exceeded the conventional framing provisions since engineered buildings
>  typically provide more story strength than these provisions. 

Then your records must be more comprehensive than the file I've compiled,
which started with Anchorage.  I'm not aware of any occurrences, and would
appreciate specifics if you have them.  Even if there have been a few
casualties, safety is, statistically, an insignificant issue when compared
against the total number of houses, and their occupants, that have
experienced strong ground shaking.  And keep in mind we are talking about
casualties due principally to failures of lateral load paths in houses.  For
the two houses that slid downhill in the Northridge event and caused
fatalities, ground failures contributed to the load  path failures.
>  3. The use of design standards should be consistent. Either the
>  conventional framing provisions should be raised to meet or exceed the
>  minimum engineered standards or vice versa.

Thoreau said, "consistency is the hobgoblin of small minds".  It's been
suggested, perhaps somewhat tongue-in-cheek, that engineers are models of
consistency.  If the present conventional framing provides provide adequate
safety, why raise them for the sake of consistency?

> After seeing the effects of
>  the Northridge Earthquake on engineered wood frame buildings, would
>  anyone propose a LOWERING of the minimum engineering standard?

Did anyone propose lowering engineering standards?  If so, then I've missed
it.  All I've seen is Dennis Wish's crusade to eliminate the conventional
framing provisions.  My previous posting was in response to one from Wish.

>  4. Engineering is supposed to "do for a dollar what any fool can do for
>  two" by colloquial definition. An engineered structure should be MORE
>  economical, not more conservative than non-engineered designs.

I'm surprised to hear this supposition from someone working in a building
department.  If you have had much contact with contractors, you surely have
heard numerous opinions and anecdotal stories to the contrary when it comes
to the consruction costs of engineered and non-engineered houses.  If you
haven't had much contact, then ask some of your veteran field inspectors.
  I'll offer a challenge: ask ten contractors who have experience with both
types of projects, and also ten of your inspectors, about their impressions
of project costs and report the results on this listserv.  Perhaps L.A. is in
a different universe, and I'll be surprised.  If so, then you might put the
question to my old friend and your new boss, Andrew Adelman, who has worked
in No. Calif. all his career until recently.

>  The conventional standards should be more (or at least as)  conservative
>  the engineered design, not more economical.  Building codes should not
>  allow less strength when less professional judgement and oversight
>  exist..

Read again my last posting, and address the regulatory compliance cost and
public policy issues.  We engineers can't wrap ourselves with the 'safety'
flag to extend our influence into areas where we have no special expertise,
such as public policies on resource allocation.    In this age of
special-interest groups, agendas and politics, the public is increasingly
skeptical about claims of "we know what's best for you".  Giving engineers a
legal monopoly on all building structural design isn't going to fly.  This is
not to say that the recently adopted conventional framing provisions are now
perfect - modifications that can be supported by observations of damage and
experiences with constructability should be submitted..

Frank Lew, SE
Orinda, CA