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fall arrest system anchor point
a fall arrest system is required to have an anchor point capable of holding 5000#. is the anchor point required to hold this 5000# without exceeding the yield stress? i have a beam that can hold 4500# in the elastic region and about 8000# in the plastic region. does this meet osha code?
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cfr 1915.159(a)(9) which is for shipyards states:
"anchorages shall be capable of supporting at least 5,000 lb per employee attached or shall be designed, installed and used as follows:
as part of a complete personal fall arrest system which maintains a safety factor of at least two; andunder the direction and supervision of a qualified person"
my interpretation is 5000 lb prescriptive is on yield of material which gives approximately 1.6 factor of safety on ultimate. if you design the "system" you need a factor of safety of 2 on ultimate for the maximum load you will see in your "system".
quote:
anchorages shall be capable of supporting at least 5,000 lb per employee attached or shall be designed, installed and used as follows
my take on the wording is that these anchorages must handle these loads as a normal condition, e.g., not require replacement or checking after such loading.
ttfn
i have designed anchorages of this type to ultimate stength. the compny for which i have designed them has a standiding proceedure that requires inspection of an anchorage point should it be subjected to a fall-protection loading.
i also note that this company has a dedicated deprtment devoted to safety and is diligent in monitoring these anchor points.
i think the safety factor of 2.0 should be applied to ultimate loading. companies like cm mockabee, who do cables and sheaves etc. typically apply their safety factors versus ultimate and this seems similar to that.
continued inspection is also a must
best to add some web or flange stiffing, cross bracing, post tention tendons (lots of options dependant on your application)...to your beam to get the 5000# with a factor of safety.
rule of thumb is...would you put on a harness and jump after the design is complete? if not, then replace the beam or add some meat!.
actually the ultimate load 5000#'s and the actual working load to which the anchor would be subjected, ie 250 #'s falling thru 6' or 8', can't remember which at the moment, are of course different. never test an existing anchor to 5000 #'s, never post the capacity of the anchor as 5000 #'s. we used to test anchors, subject them to 2500#'s pull incrementally, recording deflection, can't re
i am leaning toward the 5000# based on ultimate strength. as long as the beam is sure to arrest the fall, i see no need to strengthen. in case of a fall, the beam will be inspected after the accident, and if there is any plastic deformation, then the beam will be replaced.
if there is any code or law that requires more than this, please let me know, otherwise i will leave the beam as is.
thank you all for your posts,
weron4u
i see i'm a little late responding to this thread, but i'll put my .02 in anyway:
i work at heights everyday and am familiar with oshas regs.
the anchorage must be capable of supporting 5,000lbs. per worker. however, personnel using personal fall arrest systems with a body harness must have maximum arresting forces limited to 1,800 lbs. there's also an allowance that a 'designed/engineered' anchorage can be designed with a 2:1 safety factor, which would then be 3,600 lbs.
in reality, virtually all shock arrest/decelerating lanyards produced today limit maximum forces to around 900lbs., and that's with a big boy falling.
if you've got an anchorage that's good for 4,500lbs, you should be able to sleep well.
osha requires all pfa to be inspected after a fall, so it's reasonable to assume the anchorage should be inspected as well.
regards,
j
correct yes 'theclimber', 5000 lbs is the failure or ultimate limits state, not at all the 'specified' or 'working' load for the anchor.

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