Structural Engineer On the Fallacies of Movie Bridge Destruction (hackaday.com)

szczys writes: Suspension bridges like the Golden Gate Bridge and the Brooklyn Bridge are favorite victims for movie makers but are almost always shown to perform in violation of the laws of physics. Structural Engineer Alex Weinberg couldn't stay silent any longer. He covers how bridge collapses in several major films should have looked. The biggest offender? Christopher Nolan's The Dark Knight Rises.

Comments

Re:Well written and funny article

[Anonymous Coward]

You should have read further and into the comments as well. Catenary is indeed not a parabola, but the suspension cables are. The cables are not free-hanging, they carry a considerable mass, which makes them parabola-shaped. As soon as the bridge fails, the cables turn into catenary shape, which makes his usage of the words accurate.

Re:It's a catenary curve

[hondo77]

From your own citation:

However, in a suspension bridge with a suspended roadway, the chains or cables support the weight of the bridge, and so do not hang freely. In most cases the roadway is flat, so when the weight of the cable is negligible compared with the weight being supported, the force exerted is uniform with respect to horizontal distance, and the result is a parabola...

OMG Pacific Rim

[Solandri]

Very fun movie to watch, but wow the bad physics. TFA mentions the Golden Gate Bridge standing in the background with the center span broken. Compared to all the other physics goofs, I didn't even notice that one.

- Oil tanker swung like a baseball bat (it would buckle and snap in half just lifting it by one end).
- Helicopters carrying gigantic armored robots (a C-5 Galaxy can carry a single M1A2 Abrams tank).
- EMP-type event not affecting one robot because it's nuclear powered.
- Nuclear reactor causing a nuclear explosion (they can't do that, their fuel isn't even the right type to attain uncontrolled criticality).
- Giant monsters with exoskeletons (they would collapse under own weight). I let this one pass because of the Godzilla tradition, including the streets and buildings.

Yep, Pacific Rim was bad physics

[Firethorn]

I'm with you on all of those.

For those that might be wondering about the oil tanker(and such). Consider how strong, proportionally, insects are compared to humans. This scaling continues. It's relatively easy to make a toy helicopter that can fall from several times it's height, ram it's blades into objects, and such and still come out without damage. A helicopter big enough for people? No way.

Things like oil tankers are carefully balanced and strong where they need to be strong for their designed purpose. A tanker is designed to carry it's weight while supported on all sides by water.

It's also why Superman's hands should tear through vehicles like paper instead of lifting them, much of the time. You don't jack up so much as 1/4 of a car without using specific points that are capable of holding the structure.