Why do bridges shake when wind is high?
Wind rushes over the wall and creates an air vacuum that pulls the surface of the bridge up and down. This might not be noticeable in a typical day’s wind, but a strong, powerful wind exacerbated the effect and caused the bridge to shake and wave up and down.
What happens when a bridge vibrates?
If the mechanical resonance is strong enough, the bridge can vibrate until it collapses from the movement. A potent reminder of this was seen in June 2000, when London's Millennium Bridge opened to great fanfare. As crowds packed the bridge, their footfalls made the bridge vibrate slightly.
Why is the Golden Gate Bridge vibrating?
Since the suspension portion of the bridge is over half a mile long, the effect of the “vortex vibration” is able to magnify. Officials closed the bridge and are making plans to remove the retaining wall, and it sounds like that will solve the problem. But it might take longer for drivers to decide to take the bridge again.
Why are bridges so weak?
Sometimes low-grade or faulty materials were used, rendering the entire bridge too weak to withstand the rigors of time.
Is it normal for bridges to vibrate?
Structures like bridges and buildings, although they appear to be solid and immovable, have a natural frequency of vibration within them. A force that's applied to an object at the same frequency as the object's natural frequency will amplify the vibration of the object in an occurrence called mechanical resonance.
Why does bridge bounce?
Cambering is designed such that individual concrete slabs can flex downward to a level position under heavy loads. The bouncing is a common byproduct of bridge spans constructed with concrete slab spans. This particular design was used with the Bayside Bridge to prevent potential sagging or downward sloping.
How do you stop resonance on a bridge?
In order to mitigate fully the resonance effect in a bridge, engineers incorporate dampeners into the bridge design to interrupt the resonant waves and prevent them from growing. Another way to halt resonance is to give it less room to run wild.
What causes bridge resonance?
Every object has a natural frequency at which it likes to vibrate. When the wind drives the bridge to oscillate at its natural frequency, we say that they're in resonance. This causes the oscillations of the bridge to be amplified.
Do bridges wobble?
When the number of people walking on a bridge passes this threshold, the force of their collective footfalls pushes the bridge from side to side in sync with the bridge's minute oscillations and exacerbates the swaying.
Why do suspension bridges sway?
Most suspension bridges have a truss system built into them beneath the road to keep it more rigid and less apt to sway and twist. But suspension bridges have to be somewhat flexible during high winds. Otherwise, they may break. The combined effects of too much weight and wind can lead to breaking support cables.
Why are soldiers told to break step when crossing a bridge?
At a certain point, the bridge would start oscillating to the same rhythm as that of the marching steps. This oscillation would reach a maximum peak when the bridge can no longer sustain its own strength and hence collapses. Therefore, soldiers are ordered to break their steps while crossing a bridge.
Can a cat collapse a bridge?
But a cat? No, that's pure myth.” The story of the company of soldiers bringing down a bridge by walking over it in step is based on an actual incident. The Angers Bridge, also called the Basse-Chaîne Bridge (shown below), was a suspension over the Maine River in Angers, France.
What is buckling on a bridge?
Buckling is what happens when. the force of compression overcomes an object's ability to handle compression, and. snapping is what happens when the force of tension overcomes an object's ability to. handle tension.
Can a bridge collapse due to wind?
I'm amazed, says Nitin Gadkari. NEW DELHI: Union minister Nitin Gadkari on Monday said he was amazed at the response of an IAS officer who attributed the collapse of a portion of an under-construction road bridge in Sultanganj to 'strong winds'.
What is aeroelastic flutter on a bridge?
Aeroelastic flutter, defined as “an unstable, self-excited structural oscillation at a definite frequency where energy is extracted from the airstream by the motion of the structure”, is ubiquitous in a wide range of engineering fields.
What bridge shook itself apart?
Tacoma Narrows BridgeThe 1940 Tacoma Narrows Bridge, the first Tacoma Narrows Bridge, was a suspension bridge in the U.S. state of Washington that spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula....Tacoma Narrows Bridge (1940)Tacoma Narrows BridgeCollapsedNovember 7, 1940LocationWikimedia | © OpenStreetMap10 more rows
What happened to the Humen Bridge?
China’s state media released an account of what happened (translated): “It is reported that the Humen Bridge is under maintenance, and a 1.2-meter-high retaining wall has been added to the bridge deck, destroying the streamline of the section and causing vortex vibration.
Why are suspension bridges wind tolerant?
What does this mean? Well, part of the reason suspension bridges are wind tolerant is because they’re “streamlined,” meaning they present as little resistance to the through-flowing wind as possible. When engineers added a new four-foot wall to the suspension portion of the Humen Bridge in Guangdong, China, which opened over 20 years ago, they added what amounts to a wind-capturing sail.
When did the Tacoma narrows bridge collapse?
We were reminded of the catastrophic Tacoma Narrows bridge collapse of 1940, where a suspension bridge with a history of “wobbling” (gulp) waved itself into pieces that fell into the water below.
Where is the Humen Pearl River Bridge?
The bridge in Guangdong recently had a wind-obstructing retaining wall installed. The viral video above shows the Humen Pearl River Bridge in China that’s waving like the surface of the ocean—even when the bridge is crowded with cars.
How does the soldiers' rhythmic marching affect the vibrational frequency of the bridge?
If their frequency is closely matched to the bridge's frequency, the soldiers' rhythmic marching will amplify the vibrational frequency of the bridge. If the mechanical resonance is strong enough, the bridge can vibrate until it collapses from the movement. A potent reminder of this was seen in June 2000, when London's Millennium Bridge opened ...
When did the Broughton Suspension Bridge break?
In April 1831, a brigade of soldiers marched in step across England's Broughton Suspension Bridge. According to accounts of the time, the bridge broke apart beneath the soldiers, throwing dozens of men into the water. After this happened, the British Army reportedly sent new orders: Soldiers crossing a long bridge must "break stride," ...
When did soldiers break stride on a bridge?
(Image credit: <a href="http://www.shutterstock.com/gallery-111031p1.html">Rafal Olkis</a> | <a href="http://www.shutterstock.com">Shutterstock.com</a>) In April 1831, a brigade of soldiers marched in step across England's Broughton ...
What happens when soldiers march in unison across the structure?
If soldiers march in unison across the structure, they apply a force at the frequency of their step.
Why are bridges so damaged?
Bridge fires aren't a thing of the distant past, however. Several modern bridges have also collapsed or been severely damaged due to fire. The cause is typically the crash of a tanker truck carrying a large amount of a highly flammable substance like gasoline.
Why did the Silver Bridge collapse?
has become infamous for its connections to Mothman, a strange creature supposedly sighted near Point Pleasant in the months prior to the collapse (The 2002 Richard Gere film "The Mothman Prophecies," chronicled the story). In truth, the collapse was due to a manufacturing defect in one of the steel eyebars that held the bridge up. Years of corrosion worsened the defect until it eventually failed, resulting in the deaths of 46 people [source: LeRose].
How do floods cause bridges to collapse?
When the river passes under a bridge, the high water level smashes the debris into the bridge. If the impact doesn't destroy the bridge immediately, the weight of the piled up combined with the force of the flowing water pushing on it can bring the bridge down. This is what happened to the Conemaugh Viaduct in 1889, when the South Fork Dam in Pennsylvania collapsed, unleashing a massive torrent of water down the Little Conemaugh River [source: NPS ].
How did the Eschede train collapse?
This type of bridge collapse is extraordinarily rare, but one of the worst rail disasters in history, the Eschede train disaster, was a bridge collapse caused by train impact. In 1998, a high-speed train traveling through Germany suffered a mechanical malfunction of one of the wheels. The broken wheel struck a switch and shifted it, throwing subsequent cars onto a different track. Moving at roughly 124 miles (200 kilometers) per hour, the cars derailed and slammed into the piers of a road bridge that passed over the railroad tracks at that point. The massive impact brought the bridge down directly onto the passenger cars of the train, crushing them. As a result, 101 people died in the accident [source: Oestern ]. Eighty-three people lost their lives in a similar tragedy near Sydney, Australia in 1977 [source: ABC News ].
What caused the collapse of the I-35W bridge?
FBI agents investigate the collapse of the I-35W Bridge in Minneapolis, a disaster apparently caused by an inherent design weakness. See more bridge pictures .
What happened to the 14th Street Bridge?
Even rarer than trains crashing into bridges are airplane crashes that destroy bridges. The 1982 crash of Air Florida Flight 90 hit the 14th Street Bridge over Interstate 395 near Washington National Airport, killing several people in their cars. The bridge did not completely collapse, but did require extensive repairs [source: Wilber ].
What are the factors that affect bridge construction?
Although the general physics of bridge-building have been established for thousands of years, every bridge presents complicated factors that must be taken into consideration, such as the geology of the surrounding area, the amount of traffic, weather and construction materials. Sometimes these factors are miscalculated, or something occurs that the bridge designers didn't expect. The result can be tragic.
What caused the Tacoma narrows bridge to collapse?
Resonant frequencies are what caused the Tacoma Narrows bridge to collapse from a 40 mile per hour wind. It was a flaw in the original design. The video of the collapse is quite dramatic.
Why do kids swing higher?
Resonant frequencies are the reason that children can swing on a swing-set higher and higher, with just a little extra force applied on each swing. It's what causes a crystal glass to hum (and shatter, under the right conditions) when you circle a moistened fingertip around the rim of the glass.
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