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RE: Fall Protection

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My understanding is that you must design the anchorage (supports) for a
least 5,000 lbs.  However, no specific factor of safety is required by
OSHA.  Lifelines that allow free fall distances greater than 2 feet must be
capable "of sustaining a minimum tensile load of 5,000 lbs".   The words
minimum tensile imply that failure is the criteria.  Therefore, the
anchorage is okay if it doesn't break or yield excessively.  In other
words, many anchorages will be okay even if the 5,000 loads stresses them
all the way to the yield strength.  You may have to use lower values if
buckling, or instability problems limit the allowable stress.  A 1/3
increase is certainly okay for most anchorages for fall protection.





Mike Ritter <mritter(--nospam--at)lgt.lg.com> on 10/15/98 01:00:52 PM

Please respond to seaint(--nospam--at)seaint.org


To:   "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
cc:    (bcc: Scott A Jensen/SAJ5/LMITCO/INEEL/US)
Subject:  RE: Fall Protection




I did some anchorage calcs for a fall protection system about a year
ago.  Mine was a window washing system tie-off.  If I remember
correctly, the trick was to try to get an "engineered system" to meet
the OSHA requirements, which would produce a force less than 5000
pounds.  These "engineered systems" consist of springs and other devices
that absorb some of the energy from the falling person.  The system we
used was quite expensive, but I have noticed that even Unistrut now has
an engineered fall protection system available.  They might be able to
help reduce the force you need to design for.

In my case, I ran a few side calcs and realized that a 200 pound person
falling from a structure can easily produce the 5000 pound force.  But
both the structure and the falling individual would be better off if the
force was substantially reduced.  I used the recommendations from the
system manufacturer and designed for only about 2,000 or 2,500 pounds,
without any 1/3 stress increase in the allowables.

Hope that helped,

Mike Ritter, PE

> -----Original Message-----
> From:   Michael D Zaitz [SMTP:mzaitz(--nospam--at)surfsouth.com]
> Sent:   Thursday, October 15, 1998 1:10 PM
> To:     seaint(--nospam--at)seaint.org
> Subject:     Fall Protection
>
> Hello,
>
> Has anyone done much design related to fall protection.  The OSHA
> specification requires a force of 5000 lbs.  for the design of the
> fall
> protection supports.  The question I have is could you allow a
> one-third
> stress increase the same as done for wind for the design of the steel
> frame for a fall protection system?
>
> Thanks,
>
> Mike
>
>
>