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Re: Fall Protection System - Loading

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My apologies for not responding more timely.


You need to be very careful here. If you are referring to the end support
for a horizontal lifeline, OSHA does not stipultae the anhorage strength
requirements. Instead, they state, in 1926 sub Part M, that horizontal
lifelines are to be "designed, installed and used under the supervision of a
qualified person" (Read professional engineer experienced in the design of
fall protection systems)

This is because the end anchorage  forces are dependent upon a number of
things including:

Is the cable single span or multiple span
Total length of cable
Length of single maximum span
Cable diameter
Cable composition
Number of users
Method of attachment and arresting forces
Properties of in-line load arresting devices 

Plus many other factors including friction, sag, fall distance, clearance
distances, system  elongation etc.
 

The load you referenced may overstate, OR UNDERSTATE, the actual dynamic
reaction. Tne solution to this problem is not as straight forward as many
would think and I have seen many engineers get involved in this process only
to realize that fact at the very end.


We provide these services professionally. Visit our web site at
www.evancorp.com or contact me directly if you would like more info at
dpe(--nospam--at)evancorp.com


At 10:36 AM 11/16/1999 EST, you wrote:
>Recently, I was involved with the design of a fall protection system, for 
>personnel engaged in activities on top of trucks in petroleum product loading 
>rack.  I was asked to follow OSHA guidelines.  According to OSHA, "Lifelines 
>shall be secured above the point of operation to an anchorage or structural 
>member capable of supporting a minimum dead weight of 5,400 pounds".  Design 
>based on this requirement resulted in lot of structural steel, which seems to 
>me to be an overkill.  The project was on a fast track, so I could not do 
>enough research before sketching the details.
>
>Now that the project is behind me (except for comments from all those 
>self-styled structural engineers, like "which idiot designed this ?") I can 
>get to the bottom of the design philosophy.  I am curious to know the basis 
>on which OSHA came up with their recommendation.  Yes, it is a dynamic 
>problem, but what assumptions or tests led to the 5,400 load?  Am I justified 
>in stressing the steel members to their yield limit, considering the loading 
>to be extraordinary?  Is it possible to get theoretical basis for the 
>recommendation etc.  I am looking forward to some lively discussions on the 
>topic.  Thanks, in advance.
>
>Raj.
>
>
David P. Evangelista, PE
Evan Corp.