RussellMc wrote:
> In that case overloading a nut by a factor of two (more or less)
> killed a number of people.
> I'd feel that less than a factor of two over maximum possible loading
> is excessively low for a walkway - that's the sort of margins that you
> go to space on. And, when you DO go to space on a 1.5:1 safety margin
> (or 1.2:1 in some cases) , you find people doing up nuts with a force
> calibrated certified traceable nut driver, counting the turns and
> recording them in a log.

I only got a vague verbal description of the cause once from a structural
engineer.  There may well be reasons the actual stress factor was
considerbly more than 2x the design load.  If I remember right, it was the
bracket that actually failed, which was built differently than designed.  I
also don't know the load of the lower structure compared to the upper one.
Possibly it was several times higher.

There must be references web references you can find to this incident if yo=
u
really want to know the details.


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