How does resonance affect bridges?
How does resonance affect bridges?
In situations where the mechanical resonance is strong enough, the resulting vibrations can cause a bridge to collapse from the movement. Typically, the longer the span, the lower the resonance frequency of the bridge. Lower frequencies are also associated with large displacement amplitude vibrations.
What caused the Millennium Bridge to wobble?
According to Strogatz, the bridge was driven to sway sideways by the pedestrians as they walked across it. “Their periodic footfalls pumped energy into the bridge and caused it to move from side to side, which in turn caused the people to adjust their gaits to conform to the movement of the bridge,” he says.
How do bridges avoid resonance?
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.
Why does resonance cause bridges to collapse?
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. In this case, the Tacoma Narrows Bridge’s oscillations were amplified so much and for so long that its structure was not able to withstand the movement.
How do you calculate resonance of a bridge?
If you model your bridge as a SDOF with these properties: mass m and stiffness k. Then the natural frequency wn in radians per second is: wn=sqrt(k/m) and the cyclic natural frequency fn (in Hz) is calculated with this equation fn=wn /(2*pi).
Can a steel bridge collapse because of resonance?
Almost everything that exists has a natural frequency. Even a steel bridge can collapse because of resonance. When an object is forced to vibrate at its natural frequency, its vibration amplitude increases.
How was the Millennium Bridge engineered?
Built using ‘lateral suspension’, an engineering innovation allowing suspension bridges to be built without tall supporting columns, the Thames’ newest crossing was hit by a phenomenon called Synchronous Lateral Excitation when loads of people flooded over its shiny new deck.
What type of bridge is the Millennium Bridge?
Suspension bridgeMillennium Bridge / Bridge type
How do you stop resonance?
How to Avoid Resonance
- Adding stiffness increases the natural frequency.
- Adding mass decreases the natural frequency.
- Increasing damping reduces the peak response but widens the response range.
- Decreasing damping increases the peak response but narrows the response range.
What is bridge natural frequency?
Natural frequencies, considered to reflect bearing conditions and characterize resonance phenomena under periodic loading, are typically identified through acceleration measurement with sensors installed on bridges [1]. Nonetheless, sensor installation on a large number of bridges is not practical.
