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RE: Metal building frames blown over (was Levelling plates or shi ms ?)

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Paul,

There is a certain amount of time when erecting pre-engineered buildings
that you are vulnerable.  Each frame is set one at a time.  Until you have 2
frames erected, there is nothing to brace to.  This particular failure
occurred while they were installing the bracing after the second frame was
set.

And give the hard hats a break.  WE are the ones that have been trained and
educated to design properly for wind, and we make mistakes.  Structural
engineers are generally not part of the process in BUILDINGS to develop
erection sequence plans.  Structural engineers have generally avoided
getting into methods and means because of the increased liability.  The iron
workers have been pretty much on their own.  And it is the iron workers who
have the most at stake ...their lives.  And they are very aware of it.

I attended a meeting of iron workers after the failure.  They were pissed
that our profession does not appear interested in their problems.  We are
sitting in our offices, and they are the ones that are getting killed.

I would love to get some of my engineering colleagues out on the iron to see
what it is like.  Some call it empathy, I call it Socratic wisdom.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	ad026(--nospam--at)hwcn.org [SMTP:ad026(--nospam--at)hwcn.org]
> Sent:	Thursday, February 28, 2002 10:02 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	Metal building frames blown over (was Levelling plates or
> shims ?)
>
> > From: "Sprague, Harold O." <SpragueHO(--nospam--at)bv.com>
>
> > Good point.  Four bolts is a must!!  The OSHA Subpart R is now the law,
> and
> > a good idea.  It is so automatic with me, I did not even mention it.
>
> > For narrow bolt configurations that are popular with the 3 hinge arch
> frames
> > for pre-engineered metal buildings, it can be even more critical.  I
> have
> > seen frames like these blown over, and iron workers killed (Denver
> 1998).
> > Engineers who design these structures should run the numbers for wind on
> the
> > projected area based on a 5 year wind.  There will be a paper published
> soon
> > correlating construction wind velocities to a 5 year wind.
>
> Whack! Pre-eng takes another one up-side the head. Why doesn't anybody
> say, "Look! Another poorly designed/erected conventional steel structure
> just fell down ...?" 8-)
>
> It is unlikely that wider spacing on the anchor bolts would have done
> much in such a case.
>
> Additionally, OSHA's requirement for 4 bolts is simply an improvement
> over some of the more gross site stupidity and ignores the
> wind/stability/impact forces (now, that's poor engineering!). There will
> be erectors who assume that they don't have to provide bracing to those
> columns since OSHA has mandated a "fix".
>
> The wind susceptibility of metal building rigid frames is well
> understood by most metal building designers. Unfortunately, it is not
> well understood by some contractors and/or they try to cut corners by
> ignoring the construction bracing!!!!!
>
> Due to the deep sections commonly used, it can be possible to exceed the
> surface area of the endwall, and/or the equivalent wind force of a fully
> clad building, with just a few frames erected. It is imperative that the
> first frame erected is well stabilized and the first pair of frames
> erected includes the engineered building bracing. I have not encountered
> a manufacturer that does not include this in the erection instructions.
>
> Metal building manufacturers do not put any effort into construction
> phase analysis except in very rare circumstances. The contractors are
> rarely sophisticated enough to have it done or prefer to pay the
> insurance premium, instead.
>
> There was a failure, near Niagara Falls, last year. If I recall
> correctly:
> 1) about 10 frames fell
> 2) there was no apparent bracing of any type installed, including the
> engineered bracing
> 3) it happened on a weekend when nobody was on site (fortunately), but
> it means that they left it that way, expecting it to stand.
>
> The problem is not the framing style or quantity of bolts or spacing.
> It's the occasional void under the hard hat.
>
> --
> Paul Ransom, P. Eng.
> Civil/Structural/Project/International
> Burlington, Ontario, Canada
> <mailto:ad026(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>
>

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