My physics teacher talked about it. something about the wind and the perfect something. gosh that was in freshman year can you explain it?
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I believe the analogous motion is that of someone being pushed on a swing. The push comes at exactly the right moment to increase the motion of the swing.
The original Tacoma Narrows bridge was built without regard for the wind speed and wind intervals that could be experienced. The wind buffeted the bridge at exactly the right intervals to increase its swinging motion. The wind that day blew at exactly the fundamental frequency of the bridge's side to side swing motion. Thus this motion increased to the point of collapse.
The original Tacoma Narrows bridge was built without regard for the wind speed and wind intervals that could be experienced. The wind buffeted the bridge at exactly the right intervals to increase its swinging motion. The wind that day blew at exactly the fundamental frequency of the bridge's side to side swing motion. Thus this motion increased to the point of collapse.
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http://www.youtube.com/watch?v=3mclp9QmC…
Note the picture of the workman on the 8 foot high Stiffening Girder at the front of the video. The bridge was a scale up of a common successful bridge design at the time. Compare to the open truss work stiffening of the Golden Gate Bridge. But, it was a scale up and was in a location noted for high winds. The bridge was long and thin and at right angle to the prevailing wind off the Pacific Ocean that blew up the Narrows.
The long, thin bridge with the 8 foot high girder (solid steel) had 2 effects: 1) The girder was an 8 foot high sail on the side of the bridge. 2) The long, thin profile resulted in Aeoliean Flutter
http://en.wikipedia.org/wiki/Aeolian_vib…
Aeolian Flutter is what causes the sound in a reed instrument
The bridge often shook in the wind and was called "Galloping Girdie." In a high wind the bridge both fluttered and swung in the wind. On a high wind day the bridge swung enough that the collars that held the cables to the towers broke (It is likely the collars had already been weakened but other winds,). With the broken collars the cables cound slide back and forth over the top of the towers. Now, the bridge cound also sag on one side and then the other. The bridge was swinging, fluttering, and twisting in the wind. This put the bridge into resonance. The energy in the bridge built until there was enough to destroy it.
Note the picture of the workman on the 8 foot high Stiffening Girder at the front of the video. The bridge was a scale up of a common successful bridge design at the time. Compare to the open truss work stiffening of the Golden Gate Bridge. But, it was a scale up and was in a location noted for high winds. The bridge was long and thin and at right angle to the prevailing wind off the Pacific Ocean that blew up the Narrows.
The long, thin bridge with the 8 foot high girder (solid steel) had 2 effects: 1) The girder was an 8 foot high sail on the side of the bridge. 2) The long, thin profile resulted in Aeoliean Flutter
http://en.wikipedia.org/wiki/Aeolian_vib…
Aeolian Flutter is what causes the sound in a reed instrument
The bridge often shook in the wind and was called "Galloping Girdie." In a high wind the bridge both fluttered and swung in the wind. On a high wind day the bridge swung enough that the collars that held the cables to the towers broke (It is likely the collars had already been weakened but other winds,). With the broken collars the cables cound slide back and forth over the top of the towers. Now, the bridge cound also sag on one side and then the other. The bridge was swinging, fluttering, and twisting in the wind. This put the bridge into resonance. The energy in the bridge built until there was enough to destroy it.