I am trying to work out how I could do the calculations on a design for the attached lifeline anchor.
The attached sketch shows the concept made of 50x50 SHS inserted into 60x60 SHS which is encased in concrete.
The idea is to set one of these at either end of a cabin, attach a safety line onto each end which in turn would allow harnesses to be attached to it. This would let a couple of guys walk along a roof of a cabin.
They need to be able to support two grown men (total 190kgs) and a lifeline.
I want to be able to show if the 50x50 is sufficient or not, and if not then suggest an alternative.
I'm lost as to how to approach this and would appreciate any help.
You're going to need to establish a factor of safety (FOS) and I'm not sure how high to go. If a slip or fall occurs there will be impact or a high shock load (?) that needs to be considered.
The loading that you'll need likely calculate is cantilevered (moment) and composite - perpendicular to the safety line.
For the loading at the base of the 50x50 (+ 60x60) see:
You'll need the area moment of inertia of the cantilevered beam to do the calculations, therefore see:
or to try a different shape
So, you calculate the peak stress at the base of the cantilevered section when the peak is (expected loading * FOS) applied and compare that stress to the rated material yield or ultimate strength.
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