huangyhg

fall protection
in this thread,
to save 30% on steel, yes.
haha, thanks.
rc
all that is necessary for the triumph of evil is that good men do nothing.
edmund burke

we use an "engineered" fall arrest system that only puts about 900 lbs into the fall arrest equipment. tested many times. osha also says that if you design for two times this load - it is ok.
we use a 6' lanyard with shock absorber, full body harness and approved d-ring or hook.
we have many "saves" over the last few years.
mike, i'm familiar with the 900# load requirement as well, due to the energy absorber. however, i would apply this as a live load to the beam, and check it and the supporting connections accordingly, be it asd or lrfd. can you elaborate on your "two times this load" comment?
nutte,
is the 900# load the service/stress load case and the 5000# ultimate tensile strength load case?
if i am given a 1000# service and 4000# ultimate for a davit assembly, do i use the 1000# as a live load/impact load and design as normal?
this all seems to be so arbitrary.
rc
all that is necessary for the triumph of evil is that good men do nothing.
edmund burke

if the lanyard limts the maximum arresting force(maf) to 1800 lbs with a harness (as per osha 1926.502(d)(16)(ii)) then you design for the 1800 lbs and apply a fs of two (per 1926.502(d)(15)(i)). the 5000 lbs is not an 'ultimate' load, but rather a general case for which the ppe is not known. all of the lanyards i deal with have a maf of 900 lbs, so i design all my anchor points for 1800 lbs. sometimes i add a % of that as a lateral load. i then add it to the live load as normal.
sounds like for your case you simply need to design for an 1800 lbs live load. .66fy works for me. or whatever it is in the new code.
in my mind, the 5000# is an arbitrary load, to be used if the system is not engineered.
if the system is engineered, i use 900# as a service live load and check accordingly. i'll have to look into the "factor of safety=2" thing. my initial thought is this would be the factor of safety built into the steel specification, and should not be applied to the live load, with that total being applied to the beam.

ok, digging into the osha requirements:
osha says 2:1. body belts have not been allowed for years - too dangerous. even with a body harness - you should have a rescue plan to get to the victim within 15 minutes - 30 maximum or use some of the newer harnesses which have a drop down foot holder that allows the user to "stand" and take weight off the harness.
we design to 1800 lbs. +/- and have the testing to prove it. we actaully took 250 lb "dummies" and threw them over the side. worked great - fall arrest system that is. at 1800 lbs - it is my opinion that osha put in a 2:1 safety factor - but we design steel to say .66 or .6 which gives you another safety factor.
still doesn't mean you won't get hurt - cuts, abrasions, concussion - because you will probably hit something on your way down - even at 6'length of lanyard. but at least you will go home that night..
and clean out your pants....
true - but the 1800 lb limit is the "max" that the person should "receive" from the harness, not what the harness (hook) might "take" from the person.
so, the test of the 250 lb person dropping 6 foot = x 2 (as safety factor) would tell you want load the hook (the tie-down point and tie-down structure) would need to be designed for.
i agree, their 5000 lb requirement is only applicable if you do not do an engineering (qualified person) review.

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