Thread: Failure by design

OK, I apologize for the title, but I don't know the correct engineering term.

It relates to the following everyday experience - take a can of highly carbonated soda whose walls are presumably under considerable pressure and pull the ring. The can's structure fails exactly where it is intended to, and we pour our fizzy drink.

Fine.

Now some years ago there was a road bridge in some Western US state (I can't remember which) where high winds induced harmonic oscillations which caused the bridge to fail, with loss of life. I read that the same thinking that goes into the construction of a ring-pull Coke can is now used in bridge construction to prevent such an event in the future.

I was given very little further detail, so I don't really understand this. Not being an engineer I should be amused to have this explained to me by a Mech Eng jock

Tacoma Narrows Bridge:

Tacoma Narrows Bridge (1940) - Wikipedia, the free encyclopedia

Video:

Tacoma Narrows Bridge Collapse - YouTube

Originally Posted by Guitarist

Now some years ago there was a road bridge in some Western US state (I can't remember which) where high winds induced harmonic oscillations which caused the bridge to fail, with loss of life.

There was no loss of human life, as there was sufficient time to clear the bridge. The sole casualty was a dog (his owner was unable to induce the panicked dog to get off the bridge).

F1 & everyday car will break like a paper during a crash (and this is by design) because the obliterated pieces is intended to absorb all the energy of the impact but saves the driver, and the same thing happen with our cellphone (precursor to iPhone) where the plastic body of a cellphone exploded everwhere when the phone crashed on the floor which prevented the (expensive) screen from cracking. The front body of a car & that plastic cover are by design is weak and deformable so that it absorbs all the energy of the crash while other (expensive) part are shielded from it. This is what you meant I think?

OR
you meant that stuff is designed to have limited lifespan so it can be replaced? This is practiced by lightbulb industries in 19th century to promote consumerism. Its called "Planned obsolescence" (probably not this... lol)

A fuse will melt before your wiring catches on fire, a shear pin will break before you destroy the propellor on your boat, and a freeze plug on a car engine will pop out before you crack the engine block. I don't know of anything like that on a bridge, though.

Really they are two different things. The examples in your last post were indeed designed failures to prevent greater damage. Create a weak link, and it should fail first (a minor incovenience) as opposed to destroying the machine.

The Tacoma Narrows "Galloping Gertie" bridge failure was a faulty design, failing to consider harmonic response of the bridge to steady high winds. It taught an important lesson, which has been incorporated into new bridge designs, as well as retrofitted into existing bridges to prevent the same type of problem,