Mind-blowing bridge collapse..

[suomiviina]

I guess most of you have seen this, but in case there's someone who has missed it - take a look.

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Can someone who has read more physics than me explain how this happened? I remember the teacher saying something about oscillation and resonance but I don't remember the details...

[brahdawg]

It seems that the wind caused it by oscillating the bridge at its natural frequency.

Pretty crazy that the wind can cause something like that.

[gswarrior510]

here is another one in Russia

WEQrt_w7gN4

****ty design

[suomiviina]

It seems that the wind caused it by oscillating the bridge at its natural frequency.

Pretty crazy that the wind can cause something like that.

Yeah, the first time I saw it I was 99% sure it was fake...

[mojo85]

There was actually a cocker spaniel in that black car on the bridge that was killed :( People tried to rescue it but it was so scared it wouldnt leave and bit one of the rescuers.



According to wiki on the collapse.

" The original Tacoma Narrows Bridge was solidly built, with girders of carbon steel anchored in huge blocks of concrete. Preceding designs typically had open lattice beam trusses underneath the roadbed. This bridge was the first of its type to employ plate girders (pairs of deep I beams) to support the roadbed. With the earlier designs any wind would simply pass through the truss, but in the new design the wind would be diverted above and below the structure. Shortly after construction finished at the end of June (opened to traffic on July 1, 1940), it was discovered that the bridge would sway and buckle dangerously in relatively mild windy conditions that are common for the area, and worse during severe winds. This vibration was transverse, one-half of the central span rising while the other lowered. Drivers would see cars approaching from the other direction rise and fall, riding the violent energy wave through the bridge. However, at that time the mass of the bridge was considered to be sufficient to keep it structurally sound.


Remains of Galloping Gertie
The failure of the bridge occurred when a never-before-seen twisting mode occurred, from winds at a mild 40 miles per hour (64 km/h). This is a so-called torsional vibration mode (which is different from the transversal or longitudinal vibration mode), whereby when the left side of the roadway went down, the right side would rise, and vice versa, with the center line of the road remaining still. Specifically, it was the "second" torsional mode, in which the midpoint of the bridge remained motionless while the two halves of the bridge twisted in opposite directions. Two men proved this point by walking along the center line, unaffected by the flapping of the roadway rising and falling to each side. This vibration was caused by aeroelastic fluttering.
Fluttering is a physical phenomenon in which several degrees of freedom of a structure become coupled in an unstable oscillation driven by the wind. This movement inserts energy to the bridge during each cycle so that it neutralizes the natural damping of the structure; the composed system (bridge-fluid) therefore behaves as if it had an effective negative damping (or had positive feedback), leading to a exponentially growing response. In other words, the oscillations increase in amplitude with each cycle because the wind pumps in more energy than the flexing of the structure can dissipate, and finally drives the bridge toward failure due to excessive deflection and stress. The wind speed that causes the beginning of the fluttering phenomenon (when the effective damping becomes zero) is known as the flutter velocity. Fluttering occurs even in low-velocity winds with steady flow. Hence, bridge design must ensure that flutter velocity will be higher than the maximum mean wind speed present at the site.
Eventually, the amplitude of the motion produced by the fluttering increased beyond the strength of a vital part, in this case the suspender cables. Once several cables failed, the weight of the deck transferred to the adjacent cables that broke in turn until almost all of the central deck fell into the water below the span."

[Evolutionary1]

here is another one in Russia

WEQrt_w7gN4

****ty design

that one is fake.

[xToXiCxk23]

was the road in OP video made of a concrete/rubber mix or something? Jeez, surprised the ground didn't break apart while it was being twisted like that.

[gswarrior510]

that one is fake.

urine idiot..it was on the news

****ing bridge expert over here

[bodybuilder127]

the music makes the whole video seem so surreal....

[Dertygen]

was the road in OP video made of a concrete/rubber mix or something? Jeez, surprised the ground didn't break apart while it was being twisted like that.

large structures have an amazing amount of sway, or flex, allowed

the steel and asphalt would be good at handling it, but concrete don't never not like no tensile shear

plus you also can't see details up close and see the cracks develop


did you ever know tall buildings swing all the time?