Obligatory Calvin and Hobbes comic: https://www.gocomics.com/calvinandhobbes/1986/11/26
The most expensive number in engineering
11–20 of 176 posts
Re: The most expensive number in engineering
#12Factor of Safety or F.S. for short was something us civil engineers were taught to never forget. You got grades deducted if you solved the problem correctly but forgot to include it in the very last line.
It makes sure we calculate the loads correctly and use appropriate materials. You can't fix a bad design.
The Arkansas bridge that has been in the news lately probably would have collapsed if it wasn't for the F.S. https://www.ardot.gov/divisions/public-information/40-ms-riv...
Re: The most expensive number in engineering
#13You could just square your quantity before applying the 1.5 factor. Instead of "Our shuttle is safe up to 150% of the required speed!" design for "safe up to 150% of the required kinetic energy (1/2 m v^2)". Then you only need to design up to sqrt(1.5) = 123% of the required speed. (My point is that the scaling of the importance of quantities is arbitrary so a single safety factor doesn't make sense to be applied to…
The definition is
> breaking force divided by the expected force
Note force being used here, not energy or speed.
Re: The most expensive number in engineering
#14I'm not a civil or aerospace engineer so this could be built into the safety factor models already. Reading the post had me wondering:
If safety factor adds mass and additional mass requires additional force to accelerate is a lower safety factor safer since you'll lower the amount of force required thus increasing the structural safety?
Calculating safety factor for a given scenario feels like a complex multivariable equation. Is that the case?
Re: The most expensive number in engineering
#15Factor of Safety or F.S. for short was something us civil engineers were taught to never forget. You got grades deducted if you solved the problem correctly but forgot to include it in the very last line. It makes sure we calculate the loads correctly and use appropriate materials. You can't fix a bad design. The Arkansas bridge that has been in the news lately probably would have collapsed if it wasn't for the F.S.…
>It makes sure we calculate the loads correctly and use appropriate materials.
No, it make sure that nobody dies when you calculate the loads incorrectly and use inappropriate materials.
Re: The most expensive number in engineering
#16If you had the luxury of throwing away bridges or planes or space shuttles to test every possible circumstance, then I guess eventually the safety factor could conceivably come down to 1.0, right? You would've satisfied yourself that nothing in the real world was not in your simulations?
Re: The most expensive number in engineering
#17Factor of Safety or F.S. for short was something us civil engineers were taught to never forget. You got grades deducted if you solved the problem correctly but forgot to include it in the very last line. It makes sure we calculate the loads correctly and use appropriate materials. You can't fix a bad design. The Arkansas bridge that has been in the news lately probably would have collapsed if it wasn't for the F.S.…
> It makes sure we calculate the loads correctly and use appropriate materials. No, it make sure that nobody dies when you calculate the loads incorrectly and use inappropriate materials.
Also helps when management decides to defer maintenance for a decade or two and someone drives a truck over it that's just a bit over the weight limit what could it hurt?
Re: The most expensive number in engineering
#18Factor of Safety or F.S. for short was something us civil engineers were taught to never forget. You got grades deducted if you solved the problem correctly but forgot to include it in the very last line. It makes sure we calculate the loads correctly and use appropriate materials. You can't fix a bad design. The Arkansas bridge that has been in the news lately probably would have collapsed if it wasn't for the F.S.…
> It makes sure we calculate the loads correctly and use appropriate materials. No, it make sure that nobody dies when you calculate the loads incorrectly and use inappropriate materials.
Can’t tell if this is sarcasm.
Because of goal of civil engineering is building man made objects with public safety in mind.
Re: The most expensive number in engineering
#19If you had the luxury of throwing away bridges or planes or space shuttles to test every possible circumstance, then I guess eventually the safety factor could conceivably come down to 1.0, right? You would've satisfied yourself that nothing in the real world was not in your simulations?
A safety factor of 1.5x does not guarantee that nature will not throw 1.6x the expected force at you. That's why the author of the article calls it a "libation," because it isn't related to anyone's knowledge about the uncertainties in the situation at hand.
Re: The most expensive number in engineering
#20[deleted]