huangyhg

loads on flange of rafter
the erector wants to use a saftey harness that clips onto the top flange of the rafter. i need to figure out if the rafter will be able to hold the loads that the harness is perscribed to hold. attached is a diagram showing the loads. there is a concentraded vertical load on the flange of the beam as well as a moment. i am not sure how to check if the fange can hold this load.
thanks for any help.
you can calculate the strength of the i-beam in bending, torsion and the flange in bending but why should you and your company take responsibility for this? the liability is huge. your risk management department would choke on their lunch if you asked them about this. the erector should provide safe working conditions for his men/women. if they want to clip on to your beams, let them hire an expert to determine the safety and then monitor the erector to insure compliance with any ifs, ands, buts and conditions the analysis requires.
on the other hand, if you are the erector, you have a relatively straightforward problem in static analysis. however, if you have to ask how to do this, you'd be better off hiring someone who has experience to guide you.
my humblest opinion only...
fall arrest systems...
the loads required are ultimate limit states and the joist only needs to sustain the loads for an instant if someone does fall (impact loading). i would check the joist for strong and weak axis bending. i don't believe the structure will fail in torsion, it will twist excessivley. i wouldn't rely on the installers recommendation when they say "it's safe and they have done some testing" because they probably won't have a clue.

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