Engineers and scientists research materials on how much pressure a material can withstand, also making mini models to test out the max weight theories they have then apply that to the real mass scale structure. That's my guess anyways.
@hasher2288, thats what the faje news media wants you to think, were building two of every structure
wake up sheeple
@hasher2288, if you don’t know the answer, then just tell us
@hasher2288, they calculate the max expected load from cars/trucks on the bridge at a single moment. From there they add a factor of safety like 2 or 3 (for example). Then they design the bridge to hold 2-3x (per factor of safety) the maximum weight.
Seriously though. Generations of parents lying to their kids when they dont know is how we get dumber and dumber as a society
Same goes for elevators
@robee, how do they fit trucks in elevators though
@PacificaPelican, very carefully
They use their degrees to do a structural analysis and then throw in like a 4 or 5 factor of safety to be safe
As my dad always says: If I can't dazzle you with brilliance, I will baffle you with BS.