Safety factors account for uncertainty. Uncertainty the quality of materials, of workmanship, of unaccounted-for sources of error. Uncertainty in whether the maximum load in the spec will actually be followed.
Without a safety factor, that uncertainty means that, some of the time, some of your bridge will fall down
A safety factor of 1.0 means “the structural integrity of this construct will meet the expectations of intended use with no issues.”
A safety factor of 1.7 means “if this construct is used in a way that is 70% more abusive than anticipated, the structural integrity should remain in tact.”
You’re hand-waving enough here that you have the luxury of agreeing or disagreeing with me, well-played. Your initial response was glib and not terribly productive.
This thread started because of "the cheapest bridge that just barely won't fail"
My point was that safety factors are a part of this. A safety factor of 1.0, designing bridges so that they can perfectly withstand the expectations of intended use, means that some unacceptable % of those bridges will fall down in practice.
In other words, it's true that you can explain safety factors as:
> Assuming perfect construction, and no defects, under designed maximum load, make sure that this bridge really stays up by a wide margin
But that misses the point of why we use safety factors. Nobody is paying for a bridge to really stay up by a wide margin. Because there's no material difference between a bridge that stays up, and a bridge that really stays up, right up until the point that the weaker one falls down due to inevitable over-loading or defects in construction / materials.
That is definitely not the free market at play. It's legislative body at play.
Engineers (real ones, not software) face consequences when their work falls apart prematurely. Doubly so when it kills someone. They lose their job, their license, and they can never work in the field again.
That's why it's rare for buildings to collapse. But software collapsing is just another Monday. At best the software firm will get fined when they kill someone, but the ICs will never be held responsible.
This only works when the barrier of entry to sue is low enough to be done and when the law is applied impartially without corruption with sanctions meaningful enough , potentially company-ending, to discourage them.
At the moment you remove one of these factors, free market becomes dangerous for the people living in it.